Java tutorial
//package org.hisp.dhis.system.util; /* * Copyright (c) 2004-2013, University of Oslo * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * Neither the name of the HISP project nor the names of its contributors may * be used to endorse or promote products derived from this software without * specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ import java.util.ArrayList; import java.util.Collection; public class Main { public static void main(String[] argv) { UniqueArrayList<String> l = new UniqueArrayList<>(); l.add("a"); l.add("a"); l.add("a"); System.out.println(l); } } /** * @author Lars Helge Overland */ class UniqueArrayList<E> extends ArrayList<E> { @Override public boolean add(E e) { return super.contains(e) ? false : super.add(e); } @Override public void add(int index, E e) { if (!super.contains(e)) { super.add(index, e); } } @Override public boolean addAll(Collection<? extends E> c) { boolean modified = false; if (c != null) { for (E e : c) { if (!super.contains(e)) { super.add(e); modified = true; } } } return modified; } @Override public boolean addAll(int index, Collection<? extends E> c) { boolean modified = false; if (c != null) { for (E e : c) { if (!super.contains(e)) { super.add(index++, e); modified = true; } } } return modified; } }