diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/FlagDefinition.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/FlagDefinition.java
index 86d96fe..6b8c327 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/FlagDefinition.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/FlagDefinition.java
@@ -5,18 +5,19 @@ import java.util.Optional;
 /**
  * Represents a single flag defined in a {@link FlagGraph}.
  *
+ * @param <V> The type of the flag's value.
  * @param <S> A set of this type of flags.
  */
-public interface FlagDefinition<S> {
+public interface FlagDefinition<V, S> {
     /**
-     * The alias of the flag.
+     * The alias of the flag. A composed flag always has an alias.
      */
-    Optional<String> getAlias();
+    Optional<String> alias();
 
     /**
-     * A set containing the value of the flag, or multiple values if it is a composed flag.
+     * The value of the flag. A composed flag has no value.
      */
-    S values();
+    Optional<V> value();
 
     /**
      * Test if this flag and all its parents are present in the set.
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/FlagGraph.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/FlagGraph.java
index fafa1c0..3e44211 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/FlagGraph.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/FlagGraph.java
@@ -1,8 +1,7 @@
 package fr.louisdevie.tatsuki;
 
-import java.util.Collection;
-import java.util.Optional;
-import java.util.Set;
+import java.lang.reflect.Array;
+import java.util.*;
 
 /**
  * Represents a group of flags of type {@link V} and the relationships between
@@ -11,71 +10,128 @@ import java.util.Set;
  * @param <V> The type of the flag values.
  * @param <S> The type used to contain the flags.
  */
-public interface FlagGraph<V, S> {
+public abstract class FlagGraph<V, S> {
+    private final HashMap<V, FlagDefinition<V, S>> definitionsByValue;
+    private final HashMap<String, FlagDefinition<V, S>> definitionsByAlias;
+
+    protected FlagGraph(Collection<? extends FlagDefinition<V, S>> c) {
+        this.definitionsByValue = new HashMap<>();
+        this.definitionsByAlias = new HashMap<>();
+
+        for (var definition : c) {
+            if (definition.value().isPresent()) {
+                V value = definition.value().get();
+                if (this.definitionsByValue.put(value, definition) != null) {
+                    throw new IllegalArgumentException(String.format("Duplicate value \"%s\"", value));
+                }
+                if (definition.alias().isPresent()) {
+                    String alias = definition.alias().get();
+                    if (this.definitionsByAlias.put(alias, definition) != null) {
+                        throw new IllegalArgumentException(String.format("Duplicate alias \"%s\"", alias));
+                    }
+                }
+            } else {
+                String alias = definition.alias().orElseThrow(() ->
+                        new IllegalArgumentException("Invalid flag definition: a composed flag must always have an alias")
+                );
+                if (this.definitionsByAlias.put(alias, definition) != null) {
+                    throw new IllegalArgumentException(String.format("Duplicate alias \"%s\"", alias));
+                }
+            }
+        }
+    }
+
     /**
      * Returns the number of definitions in this graph.
      */
-    int size();
+    public int size() {
+        return this.definitionsByValue.size() +
+                (int) this.definitionsByAlias.values().stream()
+                        .filter(d -> d.value().isEmpty())
+                        .count();
+    }
 
     /**
      * Returns {@code true} if this graph contains no definitions.
      */
-    boolean isEmpty();
-
-    /**
-     * Returns {@code true} if this graph contains a definition with the specified alias.
-     */
-    boolean containsAlias(String alias);
+    public boolean isEmpty() {
+        return this.definitionsByValue.isEmpty() && this.definitionsByAlias.isEmpty();
+    }
 
     /**
      * Returns {@code true} if this graph contains a definition with the specified value.
      */
-    boolean containsValue(V value);
+    public boolean containsValue(V value) {
+        return this.definitionsByValue.containsKey(value);
+    }
+
+    /**
+     * Returns {@code true} if this graph contains a definition with the specified alias.
+     */
+    public boolean containsAlias(String alias) {
+        return this.definitionsByAlias.containsKey(alias);
+    }
 
     /**
      * Returns {@code true} if the specified definition belongs to this graph.
      */
-    boolean containsDefinition(FlagDefinition<S> definition);
-
-    /**
-     * Returns the flag definition with the specified alias.
-     *
-     * @param alias The alias of the flag.
-     *
-     * @return An {@link Optional} of the corresponding definition, or an empty
-     * {@link Optional} if there is no definition with this alias.
-     */
-    Optional<FlagDefinition<S>> definitionNamed(String alias);
+    public boolean containsDefinition(FlagDefinition<V, S> definition) {
+        return this.definitionsByValue.containsValue(definition) || this.definitionsByAlias.containsValue(definition);
+    }
 
     /**
      * Returns the flag definition with the specified value.
      *
      * @param value The base value of the flag.
-     *
      * @return An {@link Optional} of the corresponding definition, or an empty
      * {@link Optional} if there is no definition with this value.
      */
-    Optional<FlagDefinition<S>> definitionOf(V value);
+    public Optional<FlagDefinition<V, S>> definitionOf(V value) {
+        return Optional.ofNullable(this.definitionsByValue.get(value));
+    }
+
+    /**
+     * Returns the flag definition with the specified alias.
+     *
+     * @param alias The alias of the flag.
+     * @return An {@link Optional} of the corresponding definition, or an empty
+     * {@link Optional} if there is no definition with this alias.
+     */
+    public Optional<FlagDefinition<V, S>> definitionNamed(String alias) {
+        return Optional.ofNullable(this.definitionsByAlias.get(alias));
+    }
 
     /**
      * Returns a {@link Set} view of the aliases defined in this graph.
      */
-    Set<String> aliasSet();
+    public Set<String> aliasSet() {
+        return new ReadOnlyKeySet<>(this.definitionsByAlias);
+    }
 
     /**
      * Returns a {@link Set} view of the values defined in this graph.
      */
-    Set<V> valueSet();
+    public Set<V> valueSet() {
+        return new ReadOnlyKeySet<>(this.definitionsByValue);
+    }
 
     /**
-     * Returns a list of all the defined flags.
+     * Returns a {@link Set} view of all the defined flags.
      */
-    Collection<FlagDefinition<S>> definitions();
+    public Set<FlagDefinition<V, S>> definitions() {
+        return new DefinitionSet();
+    }
+
+    /**
+     * Creates a set of flags from a list of values.
+     */
+    @SuppressWarnings("unchecked")
+    public abstract S of(V... values);
 
     /**
      * Creates a set of flags from a list of aliases.
      */
-    S named(String... aliases);
+    public abstract S named(String... aliases);
 
     /**
      * Checks whether the first set of flags includes at least one of the flags
@@ -86,7 +142,7 @@ public interface FlagGraph<V, S> {
      * @param flags    - A set of flags.
      * @param required - The flags to search for in the first set.
      */
-    boolean hasAny(S flags, S required);
+    public abstract boolean hasAny(S flags, S required);
 
     /**
      * Checks whether the first set of flags includes all the flags from the
@@ -97,7 +153,7 @@ public interface FlagGraph<V, S> {
      * @param flags    - A set of flags.
      * @param required - The flags to search for in the first set.
      */
-    boolean hasAll(S flags, S required);
+    public abstract boolean hasAll(S flags, S required);
 
     /**
      * Filters a flag set so that it only contains the flags that were defined
@@ -108,7 +164,7 @@ public interface FlagGraph<V, S> {
      * @return A new set of flags.
      * @see #maximum
      */
-    S minimum(S flags);
+    public abstract S minimum(S flags);
 
     /**
      * Filters a flag set so that it only contains the flags that were defined
@@ -119,5 +175,241 @@ public interface FlagGraph<V, S> {
      * @return A new set of flags.
      * @see #minimum
      */
-    S maximum(S flags);
+    public abstract S maximum(S flags);
+
+    private static class ReadOnlyKeySet<K> implements Set<K> {
+        private final Set<K> underlying;
+
+        public ReadOnlyKeySet(HashMap<K, ?> map) {
+            this.underlying = map.keySet();
+        }
+
+        @Override
+        public int size() {
+            return this.underlying.size();
+        }
+
+        @Override
+        public boolean isEmpty() {
+            return this.underlying.isEmpty();
+        }
+
+        @Override
+        public boolean contains(Object o) {
+            return this.underlying.contains(o);
+        }
+
+        @Override
+        public Iterator<K> iterator() {
+            return this.underlying.iterator();
+        }
+
+        @Override
+        public Object[] toArray() {
+            return this.underlying.toArray();
+        }
+
+        @Override
+        public <T> T[] toArray(T[] a) {
+            return this.underlying.toArray(a);
+        }
+
+        @Override
+        public boolean add(K key) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean remove(Object o) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean containsAll(Collection<?> c) {
+            return this.underlying.containsAll(c);
+        }
+
+        @Override
+        public boolean addAll(Collection<? extends K> c) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean retainAll(Collection<?> c) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean removeAll(Collection<?> c) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public void clear() {
+            throw new UnsupportedOperationException();
+        }
+    }
+
+    private static class DefinitionIterator<V, S> implements Iterator<FlagDefinition<V, S>> {
+        private final Iterator<FlagDefinition<V, S>> byValueIterator;
+        private final Iterator<FlagDefinition<V, S>> byAliasIterator;
+        private FlagDefinition<V, S> nextDefinition;
+
+        public DefinitionIterator(HashMap<?, FlagDefinition<V, S>> byValue, HashMap<?, FlagDefinition<V, S>> byAlias) {
+            this.byValueIterator = byValue.values().iterator();
+            this.byAliasIterator = byAlias.values().iterator();
+            this.lookahead();
+        }
+
+        private void lookahead() {
+            FlagDefinition<V, S> found = null;
+            if (this.byValueIterator.hasNext()) {
+                found = this.byValueIterator.next();
+            }
+            while (found == null && this.byAliasIterator.hasNext()) {
+                found = this.byAliasIterator.next();
+                if (found.alias().isPresent()) {
+                    found = null;
+                }
+            }
+            this.nextDefinition = found;
+        }
+
+        @Override
+        public boolean hasNext() {
+            return this.nextDefinition != null;
+        }
+
+        @Override
+        public FlagDefinition<V, S> next() {
+            var nextDefinition = this.nextDefinition;
+            if (nextDefinition == null) {
+                throw new NoSuchElementException();
+            }
+            this.lookahead();
+            return nextDefinition;
+        }
+    }
+
+    private class DefinitionSet implements Set<FlagDefinition<V, S>> {
+        @Override
+        public int size() {
+            return FlagGraph.this.size();
+        }
+
+        @Override
+        public boolean isEmpty() {
+            return FlagGraph.this.isEmpty();
+        }
+
+        @Override
+        public boolean contains(Object o) {
+            // noinspection SuspiciousMethodCalls
+            return FlagGraph.this.definitionsByValue.containsValue(o) ||
+                    FlagGraph.this.definitionsByAlias.containsValue(o);
+        }
+
+        @Override
+        public Iterator<FlagDefinition<V, S>> iterator() {
+            return new DefinitionIterator<>(FlagGraph.this.definitionsByValue, FlagGraph.this.definitionsByAlias);
+        }
+
+        @Override
+        public Object[] toArray() {
+            int maxSize = FlagGraph.this.definitionsByValue.size() + FlagGraph.this.definitionsByAlias.size();
+            Object[] array = new Object[maxSize];
+            int i = 0;
+            for (var definition : FlagGraph.this.definitionsByValue.values()) {
+                array[i++] = definition;
+            }
+            for (var definition : FlagGraph.this.definitionsByAlias.values()) {
+                if (definition.value().isEmpty()) {
+                    array[i++] = definition;
+                }
+            }
+            return Arrays.copyOf(array, i);
+        }
+
+        @Override
+        @SuppressWarnings("unchecked")
+        public <T> T[] toArray(T[] a) {
+            int maxSize = FlagGraph.this.definitionsByValue.size() + FlagGraph.this.definitionsByAlias.size();
+            T[] array = (T[]) Array.newInstance(a.getClass().componentType(), maxSize);
+            ;
+            int i = 0;
+            for (var definition : FlagGraph.this.definitionsByValue.values()) {
+                array[i++] = (T) definition;
+            }
+            for (var definition : FlagGraph.this.definitionsByAlias.values()) {
+                if (definition.value().isEmpty()) {
+                    array[i++] = (T) definition;
+                }
+            }
+            if (i > a.length) {
+                return Arrays.copyOf(array, i);
+            } else {
+                Arrays.fill(a, null);
+                System.arraycopy(array, 0, a, 0, i);
+                return array;
+            }
+        }
+
+        @Override
+        public boolean add(FlagDefinition<V, S> vsFlagDefinition) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean remove(Object o) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean containsAll(Collection<?> c) {
+            boolean result = true;
+            for (Object o : c) {
+                result = this.contains(o);
+                if (!result) break;
+            }
+            return result;
+        }
+
+        @Override
+        public boolean addAll(Collection<? extends FlagDefinition<V, S>> c) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean retainAll(Collection<?> c) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean removeAll(Collection<?> c) {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public void clear() {
+            throw new UnsupportedOperationException();
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if (!(obj instanceof Set<?> otherSet)) return false;
+
+            int count = 0;
+            for (var definition : FlagGraph.this.definitionsByValue.values()) {
+                if (!otherSet.contains(definition)) return false;
+                count++;
+            }
+            for (var definition : FlagGraph.this.definitionsByAlias.values()) {
+                if (definition.value().isEmpty()) {
+                    if (!otherSet.contains(definition)) return false;
+                    count++;
+                }
+            }
+            return count == otherSet.size();
+        }
+    }
 }
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BigBitFlagGraph.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BigBitFlagGraph.java
index 75d6e78..df8dab0 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BigBitFlagGraph.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BigBitFlagGraph.java
@@ -9,56 +9,15 @@ import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 
-public class BigBitFlagGraph implements FlagGraph<BigInteger, BigInteger> {
+public class BigBitFlagGraph extends FlagGraph<BigInteger, BigInteger> {
 
-    @Override
-    public int size() {
-        return 0;
+    protected BigBitFlagGraph(Collection<FlagDefinition<BigInteger, BigInteger>> c) {
+        super(c);
     }
 
     @Override
-    public boolean isEmpty() {
-        return false;
-    }
-
-    @Override
-    public boolean containsAlias(String alias) {
-        return false;
-    }
-
-    @Override
-    public boolean containsValue(BigInteger value) {
-        return false;
-    }
-
-    @Override
-    public boolean containsDefinition(FlagDefinition<BigInteger> definition) {
-        return false;
-    }
-
-    @Override
-    public Optional<FlagDefinition<BigInteger>> definitionNamed(String alias) {
-        return Optional.empty();
-    }
-
-    @Override
-    public Optional<FlagDefinition<BigInteger>> definitionOf(BigInteger value) {
-        return Optional.empty();
-    }
-
-    @Override
-    public Set<String> aliasSet() {
-        return Set.of();
-    }
-
-    @Override
-    public Set<BigInteger> valueSet() {
-        return Set.of();
-    }
-
-    @Override
-    public Collection<FlagDefinition<BigInteger>> definitions() {
-        return List.of();
+    public BigInteger of(BigInteger... values) {
+        return null;
     }
 
     @Override
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BigBitFlagsIterator.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BigBitFlagIterator.java
similarity index 87%
rename from java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BigBitFlagsIterator.java
rename to java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BigBitFlagIterator.java
index d2e13e2..b5c1067 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BigBitFlagsIterator.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BigBitFlagIterator.java
@@ -4,11 +4,11 @@ import java.math.BigInteger;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 
-public class BigBitFlagsIterator implements Iterator<BigInteger> {
+public class BigBitFlagIterator implements Iterator<BigInteger> {
     private BigInteger value;
     private BigInteger current;
 
-    public BigBitFlagsIterator(BigInteger value) {
+    public BigBitFlagIterator(BigInteger value) {
         this.value = value;
         this.current = BigInteger.ONE;
     }
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlagGraph.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlagGraph.java
index 0209457..1791459 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlagGraph.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlagGraph.java
@@ -8,57 +8,16 @@ import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 
-public class BitFlagGraph implements FlagGraph<Integer, Integer> {
+public class BitFlagGraph extends FlagGraph<Integer, Integer> {
+    protected BitFlagGraph(Collection<FlagDefinition<Integer, Integer>> c) {
+        super(c);
+    }
+
     @Override
-    public int size() {
+    public Integer of(Integer... values) {
         return 0;
     }
 
-    @Override
-    public boolean isEmpty() {
-        return false;
-    }
-
-    @Override
-    public boolean containsAlias(String alias) {
-        return false;
-    }
-
-    @Override
-    public boolean containsValue(Integer value) {
-        return false;
-    }
-
-    @Override
-    public boolean containsDefinition(FlagDefinition<Integer> definition) {
-        return false;
-    }
-
-    @Override
-    public Optional<FlagDefinition<Integer>> definitionNamed(String alias) {
-        return Optional.empty();
-    }
-
-    @Override
-    public Optional<FlagDefinition<Integer>> definitionOf(Integer value) {
-        return Optional.empty();
-    }
-
-    @Override
-    public Set<String> aliasSet() {
-        return Set.of();
-    }
-
-    @Override
-    public Set<Integer> valueSet() {
-        return Set.of();
-    }
-
-    @Override
-    public Collection<FlagDefinition<Integer>> definitions() {
-        return List.of();
-    }
-
     @Override
     public Integer named(String... aliases) {
         return 0;
@@ -83,4 +42,5 @@ public class BitFlagGraph implements FlagGraph<Integer, Integer> {
     public Integer maximum(Integer flags) {
         return 0;
     }
+
 }
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlagsIterator.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlagIterator.java
similarity index 86%
rename from java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlagsIterator.java
rename to java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlagIterator.java
index f2c59a4..a6e8bb1 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlagsIterator.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlagIterator.java
@@ -3,11 +3,11 @@ package fr.louisdevie.tatsuki.bitflags;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 
-public class BitFlagsIterator implements Iterator<Integer> {
+public class BitFlagIterator implements Iterator<Integer> {
     private int value;
     private int current;
 
-    public BitFlagsIterator(int value) {
+    public BitFlagIterator(int value) {
         this.value = value;
         this.current = 1;
     }
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlags.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlags.java
index 4a90fc0..da2cefb 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlags.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/BitFlags.java
@@ -109,7 +109,7 @@ public final class BitFlags {
 
     private record IterableInteger(int value) implements Iterable<Integer> {
         public Iterator<Integer> iterator() {
-            return new BitFlagsIterator(this.value);
+            return new BitFlagIterator(this.value);
         }
     }
 
@@ -122,7 +122,7 @@ public final class BitFlags {
 
     private record IterableLong(long value) implements Iterable<Long> {
         public Iterator<Long> iterator() {
-            return new LongBitFlagsIterator(this.value);
+            return new LongBitFlagIterator(this.value);
         }
     }
 
@@ -135,7 +135,7 @@ public final class BitFlags {
 
     private record IterableBigInteger(BigInteger value) implements Iterable<BigInteger> {
         public Iterator<BigInteger> iterator() {
-            return new BigBitFlagsIterator(this.value);
+            return new BigBitFlagIterator(this.value);
         }
     }
 }
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/LongBitFlagGraph.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/LongBitFlagGraph.java
index 3d3c99c..84b43c5 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/LongBitFlagGraph.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/LongBitFlagGraph.java
@@ -8,56 +8,15 @@ import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 
-public class LongBitFlagGraph implements FlagGraph<Long, Long> {
+public class LongBitFlagGraph extends FlagGraph<Long, Long> {
 
-    @Override
-    public int size() {
-        return 0;
+    protected LongBitFlagGraph(Collection<FlagDefinition<Long, Long>> c) {
+        super(c);
     }
 
     @Override
-    public boolean isEmpty() {
-        return false;
-    }
-
-    @Override
-    public boolean containsAlias(String alias) {
-        return false;
-    }
-
-    @Override
-    public boolean containsValue(Long value) {
-        return false;
-    }
-
-    @Override
-    public boolean containsDefinition(FlagDefinition<Long> definition) {
-        return false;
-    }
-
-    @Override
-    public Optional<FlagDefinition<Long>> definitionNamed(String alias) {
-        return Optional.empty();
-    }
-
-    @Override
-    public Optional<FlagDefinition<Long>> definitionOf(Long value) {
-        return Optional.empty();
-    }
-
-    @Override
-    public Set<String> aliasSet() {
-        return Set.of();
-    }
-
-    @Override
-    public Set<Long> valueSet() {
-        return Set.of();
-    }
-
-    @Override
-    public Collection<FlagDefinition<Long>> definitions() {
-        return List.of();
+    public Long of(Long... values) {
+        return 0L;
     }
 
     @Override
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/LongBitFlagsIterator.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/LongBitFlagIterator.java
similarity index 85%
rename from java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/LongBitFlagsIterator.java
rename to java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/LongBitFlagIterator.java
index 93e4272..f29a27c 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/LongBitFlagsIterator.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/bitflags/LongBitFlagIterator.java
@@ -3,11 +3,11 @@ package fr.louisdevie.tatsuki.bitflags;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 
-public class LongBitFlagsIterator implements Iterator<Long> {
+public class LongBitFlagIterator implements Iterator<Long> {
     private long value;
     private long current;
 
-    public LongBitFlagsIterator(long value) {
+    public LongBitFlagIterator(long value) {
         this.value = value;
         this.current = 1L;
     }
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/FlagSetBuilder.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/FlagSetBuilder.java
new file mode 100644
index 0000000..2677f7c
--- /dev/null
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/FlagSetBuilder.java
@@ -0,0 +1,89 @@
+package fr.louisdevie.tatsuki.builders;
+
+import fr.louisdevie.tatsuki.builders.syntax.AsOrComposeValues;
+import fr.louisdevie.tatsuki.builders.syntax.AsOrRequiresOrDefineOrComposeValues;
+import fr.louisdevie.tatsuki.builders.syntax.RequiresOrDefineOrComposeValues;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+
+public abstract class FlagSetBuilder<V, R> implements AsOrRequiresOrDefineOrComposeValues<V, R>, AsOrComposeValues<V, R> {
+    private final ArrayList<PartialFlagDefinition<V>> definitions;
+    private final HashMap<String, PartialFlagDefinition<V>> aliasToDefinition;
+    private final HashMap<V, PartialFlagDefinition<V>> valueToDefinition;
+
+    private PartialFlagDefinition<V> currentDefinition;
+
+    protected FlagSetBuilder() {
+        this.definitions = new ArrayList<>();
+        this.aliasToDefinition = new HashMap<>();
+        this.valueToDefinition = new HashMap<>();
+
+        this.currentDefinition = null;
+    }
+
+    @Override
+    public RequiresOrDefineOrComposeValues<V, R> as(String alias) {
+        if (this.currentDefinition == null) {
+            throw new IllegalStateException("Attempt to set an alias while there is no current definition");
+        }
+        this.currentDefinition.setAlias(alias);
+        return this;
+    }
+
+    @Override
+    public RequiresOrDefineOrComposeValues<V, R> requires(String... aliases) {
+        throw new RuntimeException("Not implemented");
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public RequiresOrDefineOrComposeValues<V, R> requiresValues(V... values) {
+        throw new RuntimeException("Not implemented");
+    }
+
+    @Override
+    public AsOrRequiresOrDefineOrComposeValues<V, R> defineValue(V value) {
+        this.finishCurrentDefinition();
+        this.currentDefinition = new PartialValueFlagDefinition<>(value);
+        return this;
+    }
+
+    @Override
+    public AsOrComposeValues<V, R> compose(String... aliases) {
+        throw new RuntimeException("Not implemented");
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public AsOrComposeValues<V, R> composeValues(V... values) {
+        if (this.currentDefinition != null && !this.currentDefinition.isComposition()) {
+            this.finishCurrentDefinition();
+        }
+        this.currentDefinition = new PartialComposedFlagDefinition<>();
+
+        for (V value: values) {
+            this.currentDefinition.addParent(this.referenceToValue(value));
+        }
+        return this;
+    }
+
+    protected void finishCurrentDefinition() {
+        if (this.currentDefinition != null) {
+            this.definitions.add(this.currentDefinition);
+            this.currentDefinition = null;
+        }
+    }
+
+    protected ArrayList<PartialFlagDefinition<V>> partialDefinitions() {
+        return this.definitions;
+    }
+
+    private PartialFlagDefinition<V> referenceToValue(V value) {
+        var definition = this.valueToDefinition.get(value);
+        if (definition == null) {
+            definition = new ForwardReferenceByValue<>(value);
+        }
+        return definition;
+    }
+}
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/ForwardReferenceByValue.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/ForwardReferenceByValue.java
new file mode 100644
index 0000000..879ac87
--- /dev/null
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/ForwardReferenceByValue.java
@@ -0,0 +1,34 @@
+package fr.louisdevie.tatsuki.builders;
+
+class ForwardReferenceByValue<V> implements PartialFlagDefinition<V> {
+    private final V value;
+
+    public ForwardReferenceByValue(V value) {
+        this.value = value;
+    }
+
+    @Override
+    public void setAlias(String alias) {
+        throw new UnsupportedOperationException("Attempt to modify a forward reference");
+    }
+
+    @Override
+    public void addParent(PartialFlagDefinition<V> parent) {
+        throw new UnsupportedOperationException("Attempt to modify a forward reference");
+    }
+
+    @Override
+    public boolean isComposition() {
+        return false;
+    }
+
+    @Override
+    public String alias() {
+        return "";
+    }
+
+    @Override
+    public V value() {
+        return null;
+    }
+}
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/PartialComposedFlagDefinition.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/PartialComposedFlagDefinition.java
new file mode 100644
index 0000000..d4dd123
--- /dev/null
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/PartialComposedFlagDefinition.java
@@ -0,0 +1,31 @@
+package fr.louisdevie.tatsuki.builders;
+
+class PartialComposedFlagDefinition<V> implements PartialFlagDefinition<V> {
+    public PartialComposedFlagDefinition() {
+    }
+
+    @Override
+    public void setAlias(String alias) {
+        throw new RuntimeException("Not implemented");
+    }
+
+    @Override
+    public void addParent(PartialFlagDefinition<V> parent) {
+        throw new RuntimeException("Not implemented");
+    }
+
+    @Override
+    public boolean isComposition() {
+        return false;
+    }
+
+    @Override
+    public String alias() {
+        return "";
+    }
+
+    @Override
+    public V value() {
+        return null;
+    }
+}
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/PartialFlagDefinition.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/PartialFlagDefinition.java
new file mode 100644
index 0000000..980f8bd
--- /dev/null
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/PartialFlagDefinition.java
@@ -0,0 +1,13 @@
+package fr.louisdevie.tatsuki.builders;
+
+public interface PartialFlagDefinition<V> {
+    void setAlias(String alias);
+
+    void addParent(PartialFlagDefinition<V> parent);
+
+    boolean isComposition();
+
+    String alias();
+
+    V value();
+}
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/PartialValueFlagDefinition.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/PartialValueFlagDefinition.java
new file mode 100644
index 0000000..fc4c79f
--- /dev/null
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/PartialValueFlagDefinition.java
@@ -0,0 +1,38 @@
+package fr.louisdevie.tatsuki.builders;
+
+class PartialValueFlagDefinition<V> implements PartialFlagDefinition<V> {
+    private final V value;
+    private String alias;
+
+    public PartialValueFlagDefinition(V value) {
+        this.value = value;
+    }
+
+    @Override
+    public void setAlias(String alias) {
+        if (alias == null) {
+            throw new NullPointerException("null flag alias");
+        }
+        this.alias = alias;
+    }
+
+    @Override
+    public void addParent(PartialFlagDefinition<V> parent) {
+        throw new RuntimeException("Not implemented");
+    }
+
+    @Override
+    public boolean isComposition() {
+        return false;
+    }
+
+    @Override
+    public String alias() {
+        return this.alias;
+    }
+
+    @Override
+    public V value() {
+        return this.value;
+    }
+}
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/syntax/DefineOrComposeValues.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/syntax/DefineOrComposeValues.java
index 4ebf916..68d4316 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/syntax/DefineOrComposeValues.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/syntax/DefineOrComposeValues.java
@@ -1,7 +1,7 @@
 package fr.louisdevie.tatsuki.builders.syntax;
 
 
-public interface DefineOrComposeValues<V, R> extends Root<R> {
+public interface DefineOrComposeValues<V, R> {
     /**
      * Define a flag with the given value.
      *
@@ -26,4 +26,9 @@ public interface DefineOrComposeValues<V, R> extends Root<R> {
      */
     @SuppressWarnings("unchecked")
     AsOrComposeValues<V, R> composeValues(V... values);
+
+    /**
+     * Build a flag set with the flags previously defined.
+     */
+    R build();
 }
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/syntax/Root.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/syntax/Root.java
deleted file mode 100644
index badf502..0000000
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/builders/syntax/Root.java
+++ /dev/null
@@ -1,12 +0,0 @@
-package fr.louisdevie.tatsuki.builders.syntax;
-
-/**
- * Builder syntax root.
- * @param <R> The result type produced by the builder.
- */
-public interface Root<R> {
-    /**
-     * Build a flag set with the flags previously defined.
-     */
-    R build();
-}
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/CollectionFlagGraphBuilder.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/CollectionFlagGraphBuilder.java
deleted file mode 100644
index c129e06..0000000
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/CollectionFlagGraphBuilder.java
+++ /dev/null
@@ -1,27 +0,0 @@
-package fr.louisdevie.tatsuki.collections;
-
-import fr.louisdevie.tatsuki.builders.syntax.AsOrComposeValues;
-import fr.louisdevie.tatsuki.builders.syntax.AsOrRequiresOrDefineOrComposeValues;
-import fr.louisdevie.tatsuki.builders.syntax.DefineOrComposeValues;
-
-class CollectionFlagGraphBuilder<E> implements DefineOrComposeValues<E, SetFlagGraph<E>> {
-    @Override
-    public AsOrRequiresOrDefineOrComposeValues<E, SetFlagGraph<E>> defineValue(E value) {
-        return null;
-    }
-
-    @Override
-    public AsOrComposeValues<E, SetFlagGraph<E>> compose(String... aliases) {
-        return null;
-    }
-
-    @Override
-    public AsOrComposeValues<E, SetFlagGraph<E>> composeValues(E... values) {
-        return null;
-    }
-
-    @Override
-    public SetFlagGraph<E> build() {
-        return null;
-    }
-}
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/SetFlagDefinition.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/SetFlagDefinition.java
index 4295098..0dadbd4 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/SetFlagDefinition.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/SetFlagDefinition.java
@@ -1,19 +1,32 @@
 package fr.louisdevie.tatsuki.collections;
 
 import fr.louisdevie.tatsuki.FlagDefinition;
+import fr.louisdevie.tatsuki.builders.PartialFlagDefinition;
 
 import java.util.Optional;
 import java.util.Set;
 
-class SetFlagDefinition<E> implements FlagDefinition<Set<E>> {
-    @Override
-    public Optional<String> getAlias() {
-        return Optional.empty();
+class SetFlagDefinition<E> implements FlagDefinition<E, Set<E>> {
+    private final String alias;
+    private final E value;
+
+    private SetFlagDefinition(String alias, E value) {
+        this.alias = alias;
+        this.value = value;
+    }
+
+    public static <E> SetFlagDefinition<E> fromPartial(PartialFlagDefinition<E> partialFlagDefinition) {
+        return new SetFlagDefinition<>(partialFlagDefinition.alias(), partialFlagDefinition.value());
     }
 
     @Override
-    public Set<E> values() {
-        return Set.of();
+    public Optional<String> alias() {
+        return Optional.ofNullable(this.alias);
+    }
+
+    @Override
+    public Optional<E> value() {
+        return Optional.ofNullable(this.value);
     }
 
     @Override
diff --git a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/SetFlagGraph.java b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/SetFlagGraph.java
index a520971..2e5ce69 100644
--- a/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/SetFlagGraph.java
+++ b/java/tatsuki/src/main/java/fr/louisdevie/tatsuki/collections/SetFlagGraph.java
@@ -1,71 +1,27 @@
 package fr.louisdevie.tatsuki.collections;
 
 import fr.louisdevie.tatsuki.FlagGraph;
+import fr.louisdevie.tatsuki.builders.FlagSetBuilder;
 import fr.louisdevie.tatsuki.builders.syntax.DefineOrComposeValues;
-import fr.louisdevie.tatsuki.FlagDefinition;
 
-import java.util.Collection;
-import java.util.List;
-import java.util.Optional;
-import java.util.Set;
-
-public class SetFlagGraph<E> implements FlagGraph<E, Set<E>> {
-    public static <E> DefineOrComposeValues<E, SetFlagGraph<E>> builder() {
-        return new CollectionFlagGraphBuilder<>();
-    }
+import java.util.*;
+import java.util.stream.Collectors;
 
+public class SetFlagGraph<E> extends FlagGraph<E, Set<E>> {
     SetFlagGraph(Collection<SetFlagDefinition<E>> c) {
+        super(c);
+    }
 
+    public static <E> DefineOrComposeValues<E, SetFlagGraph<E>> builder() {
+        return new Builder<>();
     }
 
     @Override
-    public int size() {
-        return 0;
-    }
-
-    @Override
-    public boolean isEmpty() {
-        return false;
-    }
-
-    @Override
-    public boolean containsAlias(String alias) {
-        return false;
-    }
-
-    @Override
-    public boolean containsValue(E value) {
-        return false;
-    }
-
-    @Override
-    public boolean containsDefinition(FlagDefinition<Set<E>> definition) {
-        return false;
-    }
-
-    @Override
-    public Optional<FlagDefinition<Set<E>>> definitionNamed(String alias) {
-        return Optional.empty();
-    }
-
-    @Override
-    public Optional<FlagDefinition<Set<E>>> definitionOf(E value) {
-        return Optional.empty();
-    }
-
-    @Override
-    public Set<String> aliasSet() {
-        return Set.of();
-    }
-
-    @Override
-    public Set<E> valueSet() {
-        return Set.of();
-    }
-
-    @Override
-    public Collection<FlagDefinition<Set<E>>> definitions() {
-        return List.of();
+    @SuppressWarnings("unchecked")
+    public Set<E> of(E... values) {
+        return Arrays.stream(values)
+                .filter(this::containsValue)
+                .collect(Collectors.toUnmodifiableSet());
     }
 
     @Override
@@ -92,4 +48,13 @@ public class SetFlagGraph<E> implements FlagGraph<E, Set<E>> {
     public Set<E> maximum(Set<E> flags) {
         return Set.of();
     }
+
+    static class Builder<E> extends FlagSetBuilder<E, SetFlagGraph<E>> {
+        @Override
+        public SetFlagGraph<E> build() {
+            this.finishCurrentDefinition();
+            var definitions = this.partialDefinitions().stream().map(SetFlagDefinition::fromPartial).toList();
+            return new SetFlagGraph<>(definitions);
+        }
+    }
 }
diff --git a/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/FlagGraphTests.java b/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/FlagGraphTests.java
new file mode 100644
index 0000000..e169af8
--- /dev/null
+++ b/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/FlagGraphTests.java
@@ -0,0 +1,146 @@
+package fr.louisdevie.tatsuki;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Set;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class FlagGraphTests {
+    @Test
+    public void size() {
+        final var noFlags = new MockFlagGraph();
+
+        assertEquals(0, noFlags.size());
+
+        final var flags = new MockFlagGraph(
+                new MockFlagDefinition("A", "1"),
+                new MockFlagDefinition("B", null),
+                new MockFlagDefinition(null, "2")
+        );
+
+        assertEquals(3, flags.size());
+    }
+
+    @Test
+    public void isEmpty() {
+        final var noFlags = new MockFlagGraph();
+
+        assertTrue(noFlags.isEmpty());
+
+        final var flags = new MockFlagGraph(
+                new MockFlagDefinition("A", "x"),
+                new MockFlagDefinition("B", null),
+                new MockFlagDefinition(null, "y")
+        );
+
+        assertFalse(flags.isEmpty());
+    }
+
+    @Test
+    public void containsValue() {
+        final var flags = new MockFlagGraph(
+                new MockFlagDefinition("A", "x"),
+                new MockFlagDefinition("B", null),
+                new MockFlagDefinition(null, "y")
+        );
+
+        assertTrue(flags.containsValue("A"));
+        assertTrue(flags.containsValue("B"));
+        assertFalse(flags.containsValue("C"));
+    }
+
+    @Test
+    public void containsAlias() {
+        final var flags = new MockFlagGraph(
+                new MockFlagDefinition("A", "x"),
+                new MockFlagDefinition("B", null),
+                new MockFlagDefinition(null, "y")
+        );
+
+        assertTrue(flags.containsAlias("x"));
+        assertTrue(flags.containsAlias("y"));
+        assertFalse(flags.containsAlias("z"));
+    }
+
+    @Test
+    public void containsDefinition() {
+        final var inGraph = new MockFlagDefinition("A", "x");
+        final var notInGraph = new MockFlagDefinition("B", "y");
+        final var flags = new MockFlagGraph(inGraph);
+
+        assertTrue(flags.containsDefinition(inGraph));
+        assertFalse(flags.containsDefinition(notInGraph));
+    }
+
+    @Test
+    public void definitionOf() {
+        final var x = new MockFlagDefinition("A", "x");
+        final var y = new MockFlagDefinition("B", "y");
+        final var flags = new MockFlagGraph(x, y);
+
+        assertTrue(flags.definitionOf("A").isPresent());
+        assertSame(x, flags.definitionOf("A").get());
+
+        assertTrue(flags.definitionOf("B").isPresent());
+        assertSame(y, flags.definitionOf("B").get());
+
+        assertTrue(flags.definitionOf("C").isEmpty());
+    }
+
+    @Test
+    public void definitionNamed() {
+        final var x = new MockFlagDefinition("A", "x");
+        final var y = new MockFlagDefinition("B", "y");
+        final var flags = new MockFlagGraph(x, y);
+
+        assertTrue(flags.definitionNamed("x").isPresent());
+        assertSame(x, flags.definitionNamed("x").get());
+
+        assertTrue(flags.definitionNamed("y").isPresent());
+        assertSame(y, flags.definitionNamed("y").get());
+
+        assertTrue(flags.definitionNamed("z").isEmpty());
+    }
+
+    @Test
+    public void aliasSet() {
+        final var flags = new MockFlagGraph(
+                new MockFlagDefinition("A", "x"),
+                new MockFlagDefinition("B", null),
+                new MockFlagDefinition(null, "y")
+        );
+
+        assertEquals(Set.of("x", "y"), flags.aliasSet());
+
+        assertThrows(UnsupportedOperationException.class, () -> flags.aliasSet().remove("x"));
+        assertThrows(UnsupportedOperationException.class, () -> flags.aliasSet().add("z"));
+    }
+
+    @Test
+    public void valueSet() {
+        final var flags = new MockFlagGraph(
+                new MockFlagDefinition("A", "x"),
+                new MockFlagDefinition("B", null),
+                new MockFlagDefinition(null, "y")
+        );
+
+        assertEquals(Set.of("A", "B"), flags.valueSet());
+
+        assertThrows(UnsupportedOperationException.class, () -> flags.valueSet().remove("A"));
+        assertThrows(UnsupportedOperationException.class, () -> flags.valueSet().add("C"));
+    }
+
+    @Test
+    public void definitions() {
+        final var x = new MockFlagDefinition("A", "x");
+        final var B = new MockFlagDefinition("B", null);
+        final var y = new MockFlagDefinition(null, "y");
+        final var flags = new MockFlagGraph(x, B, y);
+
+        assertEquals(Set.of(x, B, y), flags.definitions());
+
+        assertThrows(UnsupportedOperationException.class, () -> flags.valueSet().remove("A"));
+        assertThrows(UnsupportedOperationException.class, () -> flags.valueSet().add("C"));
+    }
+}
diff --git a/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/MockFlagDefinition.java b/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/MockFlagDefinition.java
new file mode 100644
index 0000000..2a322ca
--- /dev/null
+++ b/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/MockFlagDefinition.java
@@ -0,0 +1,38 @@
+package fr.louisdevie.tatsuki;
+
+import java.util.Optional;
+
+public class MockFlagDefinition implements FlagDefinition<String, String> {
+    private final String value;
+    private final String alias;
+
+    public MockFlagDefinition(String value, String alias) {
+        this.value = value;
+        this.alias = alias;
+    }
+
+    @Override
+    public Optional<String> alias() {
+        return Optional.ofNullable(this.alias);
+    }
+
+    @Override
+    public Optional<String> value() {
+        return Optional.ofNullable(this.value);
+    }
+
+    @Override
+    public boolean isIn(String set) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public String addTo(String set) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public String removeFrom(String set) {
+        throw new UnsupportedOperationException();
+    }
+}
diff --git a/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/MockFlagGraph.java b/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/MockFlagGraph.java
new file mode 100644
index 0000000..dd3cbdc
--- /dev/null
+++ b/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/MockFlagGraph.java
@@ -0,0 +1,40 @@
+package fr.louisdevie.tatsuki;
+
+import java.util.Arrays;
+
+public class MockFlagGraph extends FlagGraph<String, String> {
+    @SafeVarargs
+    public MockFlagGraph(FlagDefinition<String, String>... definitions) {
+        super(Arrays.stream(definitions).toList());
+    }
+
+    @Override
+    public String of(String... values) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public String named(String... aliases) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public boolean hasAny(String flags, String required) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public boolean hasAll(String flags, String required) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public String minimum(String flags) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public String maximum(String flags) {
+        throw new UnsupportedOperationException();
+    }
+}
diff --git a/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/collections/CollectionFlagGraphTests.java b/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/collections/SetFlagGraphTests.java
similarity index 68%
rename from java/tatsuki/src/test/java/fr/louisdevie/tatsuki/collections/CollectionFlagGraphTests.java
rename to java/tatsuki/src/test/java/fr/louisdevie/tatsuki/collections/SetFlagGraphTests.java
index 2a55d5e..0a5c9b7 100644
--- a/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/collections/CollectionFlagGraphTests.java
+++ b/java/tatsuki/src/test/java/fr/louisdevie/tatsuki/collections/SetFlagGraphTests.java
@@ -6,7 +6,20 @@ import java.util.Set;
 
 import static org.junit.jupiter.api.Assertions.*;
 
-public class CollectionFlagGraphTests {
+public class SetFlagGraphTests {
+    @Test
+    public void of() {
+        final var flags = SetFlagGraph.<Integer>builder()
+                .defineValue(12).as("a")
+                .defineValue(45).as("b")
+                .defineValue(78).as("c")
+                .build();
+
+        assertEquals(Set.of(), flags.of());
+        assertEquals(Set.of(12), flags.of(12));
+        assertEquals(Set.of(12, 78), flags.of(12, 54, 78));
+    }
+
     @Test
     public void named() {
         final var flags = SetFlagGraph.<Integer>builder()
@@ -16,9 +29,9 @@ public class CollectionFlagGraphTests {
                 .compose("a", "b").as("ab")
                 .build();
 
-        assertEquals(Set.of(), flags.named()) ;
-        assertEquals(Set.of(12), flags.named("a")) ;
-        assertEquals(Set.of(12, 45, 78), flags.named("ab", "c")) ;
+        assertEquals(Set.of(), flags.named());
+        assertEquals(Set.of(12), flags.named("a"));
+        assertEquals(Set.of(12, 45, 78), flags.named("ab", "c"));
     }
 
     @Test
@@ -59,11 +72,11 @@ public class CollectionFlagGraphTests {
                 .defineValue(78).requiresValues(45)
                 .build();
 
-        assertEquals(Set.of(), flags.maximum(Set.of())) ;
-        assertEquals(Set.of(12), flags.maximum(Set.of(12))) ;
-        assertEquals(Set.of(12, 45), flags.maximum(Set.of(45))) ;
-        assertEquals(Set.of(12, 45, 78), flags.maximum(Set.of(78))) ;
-        assertEquals(Set.of(), flags.maximum(Set.of(99))) ;
+        assertEquals(Set.of(), flags.maximum(Set.of()));
+        assertEquals(Set.of(12), flags.maximum(Set.of(12)));
+        assertEquals(Set.of(12, 45), flags.maximum(Set.of(45)));
+        assertEquals(Set.of(12, 45, 78), flags.maximum(Set.of(78)));
+        assertEquals(Set.of(), flags.maximum(Set.of(99)));
     }
 
     @Test
@@ -74,12 +87,12 @@ public class CollectionFlagGraphTests {
                 .defineValue(78).requiresValues(45)
                 .build();
 
-        assertEquals(Set.of(), flags.minimum(Set.of())) ;
-        assertEquals(Set.of(12), flags.minimum(Set.of(12))) ;
-        assertEquals(Set.of(), flags.minimum(Set.of(45))) ;
-        assertEquals(Set.of(12, 45), flags.minimum(Set.of(12, 45))) ;
-        assertEquals(Set.of(12), flags.minimum(Set.of(12, 78))) ;
-        assertEquals(Set.of(12, 45, 78), flags.minimum(Set.of(12, 45, 78))) ;
-        assertEquals(Set.of(), flags.minimum(Set.of(99))) ;
+        assertEquals(Set.of(), flags.minimum(Set.of()));
+        assertEquals(Set.of(12), flags.minimum(Set.of(12)));
+        assertEquals(Set.of(), flags.minimum(Set.of(45)));
+        assertEquals(Set.of(12, 45), flags.minimum(Set.of(12, 45)));
+        assertEquals(Set.of(12), flags.minimum(Set.of(12, 78)));
+        assertEquals(Set.of(12, 45, 78), flags.minimum(Set.of(12, 45, 78)));
+        assertEquals(Set.of(), flags.minimum(Set.of(99)));
     }
 }