Here you can find the source of join(Collection> collection, String sep)
public static String join(Collection<?> collection, String sep)
//package com.java2s; /******************************************************************************* * /* ww w. j a va2 s . c o m*/ * Copyright 2010 Alexandru Craciun, and individual contributors as indicated * by the @authors tag. * * This is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation; either version 3 of * the License, or (at your option) any later version. * * This software is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this software; if not, write to the Free * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA * 02110-1301 USA, or see the FSF site: http://www.fsf.org. ******************************************************************************/ import java.util.Collection; public class Main { public static String join(Collection<?> collection, String sep) { StringBuilder s = new StringBuilder(); for (Object obj : collection) { if (s.length() > 0) { s.append(sep); } if (obj == null) { s.append(""); } else { s.append(obj.toString()); } } return s.toString(); } }