Java Collection Join join(Collection collection, String separator)

Description

Joins the elements of the provided Collection into a single String containing the provided elements.

No delimiter is added before or after the list.

License

Apache License

Parameter

Parameter	Description
collection	the <code>Collection</code> of values to join together, may be null
separator	the separator character to use, null treated as ""

Return

the joined String, null if null iterator input

Declaration

public static String join(Collection collection, String separator)

Method Source Code


//package com.java2s;
/*/*from  w  ww  .  j  a v  a  2s  .c  o m*/
 * Apache Commons Lang
 *
 * Copyright 2010 The Apache Software Foundation
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.Collection;
import java.util.Iterator;

public class Main {
    /**
     * <p>Joins the elements of the provided <code>Collection</code> into
     * a single String containing the provided elements.</p>
     * <p/>
     * <p>No delimiter is added before or after the list.
     * A <code>null</code> separator is the same as an empty String ("").</p>
     * <p/>
     *
     * @param collection the <code>Collection</code> of values to join together, may be null
     * @param separator  the separator character to use, null treated as ""
     * @return the joined String, <code>null</code> if null iterator input
     * @since 2.3
     */
    public static String join(Collection collection, String separator) {
        if (collection == null) {
            return null;
        }
        return join(collection.iterator(), separator);
    }

    /**
     * <p>Joins the elements of the provided <code>Iterator</code> into
     * a single String containing the provided elements.</p>
     * <p/>
     * <p>No delimiter is added before or after the list.
     * A <code>null</code> separator is the same as an empty String ("").</p>
     * <p/>
     *
     * @param iterator  the <code>Iterator</code> of values to join together, may be null
     * @param separator the separator character to use, null treated as ""
     * @return the joined String, <code>null</code> if null iterator input
     */
    public static String join(Iterator iterator, String separator) {
        // handle null, zero and one elements before building a buffer
        if (iterator == null) {
            return null;
        }
        if (!iterator.hasNext()) {
            return "";
        }

        Object first = iterator.next();

        if (!iterator.hasNext()) {
            return toString(first);
        }

        // two or more elements
        StringBuffer buf = new StringBuffer(256); // Java default is 16, probably too small
        if (first != null) {
            buf.append(first);
        }

        while (iterator.hasNext()) {
            if (separator != null) {
                buf.append(separator);
            }
            Object obj = iterator.next();
            if (obj != null) {
                buf.append(obj);
            }
        }
        return buf.toString();
    }

    /**
     * <p>Gets the <code>toString</code> of an <code>Object</code> returning
     * an empty string ("") if <code>null</code> input.</p>
     * <p/>
     * <pre>
     * ObjectUtils.toString(null)         = ""
     * ObjectUtils.toString("")           = ""
     * ObjectUtils.toString("bat")        = "bat"
     * ObjectUtils.toString(Boolean.TRUE) = "true"
     * </pre>
     *
     * @param obj the Object to <code>toString</code>, may be null
     * @return the passed in Object's toString, or nullStr if <code>null</code> input
     * @see String#valueOf(Object)
     * @since 2.0
     */
    public static String toString(Object obj) {
        return obj == null ? "" : obj.toString();
    }
}