Add Registry

Core/src/main/java/fr/altarik/toolbox/core/Registry.java

@@ -0,0 +1,51 @@
+package fr.altarik.toolbox.core;
+
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Objects;
+
+public abstract class Registry<T, U> {
+
+    protected final HashMap<T, U> registry = new HashMap<>();
+
+    /**
+     * Return a set view of the keys contained in the registry.
+     * @return An iterator view of the keys contained in the registry
+     */
+    public Iterator<T> keySet() {
+        return registry.keySet().iterator();
+    }
+
+    /**
+     * Returns true if this registry contains the key.
+     * @param key the key whose presence in the registry is to be tested
+     * @return Returns true if this registry contains the key, false otherwise
+     */
+    public boolean containsKey(T key) {
+        return registry.containsKey(key);
+    }
+
+    /**
+     * Returns the containing value represented by a specific key, or {@code null} if the registry do not contain the key
+     * @param key the key whose associated value is to be returned
+     * @return The value to which the specified key is represented, or {@code null} if the registry do not contain the key
+     */
+    public @Nullable U getValue(T key) {
+        return registry.get(key);
+    }
+
+    /**
+     * If the specified key is not already associated with a value, associate it with the given value.
+     * @param key Key to which the specified value is to be associated
+     * @param value value to be associated with the specified key
+     * @throws NullPointerException if key or value is null
+     */
+    public void register(@NotNull T key, @NotNull U value) {
+        registry.putIfAbsent(Objects.requireNonNull(key), Objects.requireNonNull(value));
+    }
+
+}
+