Here you can find the source of copy(Map
public static <K, E> Map<K, List<E>> copy(Map<K, List<E>> original)
//package com.java2s; /**//from ww w . j a v a 2 s . c o m * JBoss, Home of Professional Open Source * Copyright Red Hat, Inc., and individual contributors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Map.Entry; public class Main { public static <K, E> Map<K, List<E>> copy(Map<K, List<E>> original) { Map<K, List<E>> copy = new HashMap<K, List<E>>(); for (Entry<K, List<E>> entry : original.entrySet()) { copy.put(entry.getKey(), new ArrayList<E>(entry.getValue())); } return copy; } }