icu4j/main/classes/core/src/com/ibm/icu/impl/CollectionSet.java

// © 2018 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html#License
package com.ibm.icu.impl;

import java.util.Collection;
import java.util.Iterator;
import java.util.Set;

/**
 * A wrapper around java.util.Collection that implements java.util.Set. This class keeps a pointer to the
 * Collection and does not persist any data on its own.
 *
 * Useful when you need a Set but creating a HashSet is too expensive.
 *
 * IMPORTANT: The elements of the Collection *must* be unique! This class does not check.
 */
public class CollectionSet<E> implements Set<E> {

    private final Collection<E> data;

    public CollectionSet(Collection<E> data) {
        this.data = data;
    }

    @Override
    public int size() {
        return data.size();
    }

    @Override
    public boolean isEmpty() {
        return data.isEmpty();
    }

    @Override
    public boolean contains(Object o) {
        return data.contains(o);
    }

    @Override
    public Iterator<E> iterator() {
        return data.iterator();
    }

    @Override
    public Object[] toArray() {
        return data.toArray();
    }

    @Override
    public <T> T[] toArray(T[] a) {
        return data.toArray(a);
    }

    @Override
    public boolean add(E e) {
        return data.add(e);
    }

    @Override
    public boolean remove(Object o) {
        return data.remove(o);
    }

    @Override
    public boolean containsAll(Collection<?> c) {
        return data.containsAll(c);
    }

    @Override
    public boolean addAll(Collection<? extends E> c) {
        return data.addAll(c);
    }

    @Override
    public boolean retainAll(Collection<?> c) {
        return data.retainAll(c);
    }

    @Override
    public boolean removeAll(Collection<?> c) {
        return data.removeAll(c);
    }

    @Override
    public void clear() {
        data.clear();
    }
}