Join all the elements of a string array into a single String. - Java java.lang

Java examples for java.lang:String Join

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Description

Join all the elements of a string array into a single String.

Demo Code

/*//from  w  w  w .  jav  a  2s . co m
 * Static String formatting and query routines.
 * Copyright (C) 2001-2005 Stephen Ostermiller
 * http://ostermiller.org/contact.pl?regarding=Java+Utilities
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * See COPYING.TXT for details.
 */
//package com.java2s;

public class Main {
    public static void main(String[] argv) {
        String[] array = new String[] { "1", "abc", "level", null,
                "java2s.com", "asdf 123" };
        System.out.println(join(array));
    }

    /**
     * Join all the elements of a string array into a single
     * String.
     * <p>
     * If the given array empty an empty string
     * will be returned.  Null elements of the array are allowed
     * and will be treated like empty Strings.
     *
     * @param array Array to be joined into a string.
     * @return Concatenation of all the elements of the given array.
     * @throws NullPointerException if array is null.
     *
     * @since ostermillerutils 1.05.00
     */
    public static String join(String[] array) {
        return join(array, "");
    }

    /**
     * Join all the elements of a string array into a single
     * String.
     * <p>
     * If the given array empty an empty string
     * will be returned.  Null elements of the array are allowed
     * and will be treated like empty Strings.
     *
     * @param array Array to be joined into a string.
     * @param delimiter String to place between array elements.
     * @return Concatenation of all the elements of the given array with the the delimiter in between.
     * @throws NullPointerException if array or delimiter is null.
     *
     * @since ostermillerutils 1.05.00
     */
    public static String join(String[] array, String delimiter) {
        // Cache the length of the delimiter
        // has the side effect of throwing a NullPointerException if
        // the delimiter is null.
        int delimiterLength = delimiter.length();

        // Nothing in the array return empty string
        // has the side effect of throwing a NullPointerException if
        // the array is null.
        if (array.length == 0)
            return "";

        // Only one thing in the array, return it.
        if (array.length == 1) {
            if (array[0] == null)
                return "";
            return array[0];
        }

        // Make a pass through and determine the size
        // of the resulting string.
        int length = 0;
        for (int i = 0; i < array.length; i++) {
            if (array[i] != null)
                length += array[i].length();
            if (i < array.length - 1)
                length += delimiterLength;
        }

        // Make a second pass through and concatenate everything
        // into a string buffer.
        StringBuffer result = new StringBuffer(length);
        for (int i = 0; i < array.length; i++) {
            if (array[i] != null)
                result.append(array[i]);
            if (i < array.length - 1)
                result.append(delimiter);
        }

        return result.toString();
    }
}

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