Java List Join join(String separator, List elements)

Description

Returns a string containing all elements concatenated by a specified separator.

License

Open Source License

Parameter

Parameter	Description
separator	Separator string.
elements	List of elements that should be concatenated.

Return

a concatenated string.

Declaration

public static String join(String separator, List<?> elements) 

Method Source Code

//package com.java2s;
/* ******************************************************************************
 * Copyright (c) 2006-2013 XMind Ltd. and others.
 *
 * This file is a part of XMind 3. XMind releases 3 and
 * above are dual-licensed under the Eclipse Public License (EPL),
 * which is available at http://www.eclipse.org/legal/epl-v10.html
 * and the GNU Lesser General Public License (LGPL),
 * which is available at http://www.gnu.org/licenses/lgpl.html
 * See http://www.xmind.net/license.html for details.
 *
 * Contributors://w w w. j  ava  2s  .  c  o  m
 *     XMind Ltd. - initial API and implementation
 *******************************************************************************/

import java.util.ArrayList;
import java.util.Arrays;

import java.util.List;

public class Main {
    /**
     * Returns a string containing all elements concatenated by a specified
     * separator.
     *
     * @param separator
     *            Separator string.
     * @param elements
     *            List of elements that should be concatenated.
     * @return a concatenated string.
     */
    public static String join(String separator, List<?> elements) {
        if (elements == null || elements.size() == 0) {
            return ""; //$NON-NLS-1$
        }
        StringBuffer sb = new StringBuffer(elements.size() * 3);
        int i = 0;
        for (Object elem : elements) {
            if (i++ > 0) {
                sb.append(separator);
            }
            sb.append(format(elem));
        }
        return sb.toString();
    }

    /**
     * Returns a string containing all elements concatenated by a specified
     * separator.
     *
     * @param separator
     *            Separator string.
     * @param elements
     *            List of elements that should be concatenated.
     * @return a concatenated string.
     */
    public static String join(String separator, Object... elements) {
        if (elements == null || elements.length == 0) {
            return ""; //$NON-NLS-1$
        }
        return join(separator, Arrays.asList(elements));
    }

    /**
     * Returns a string with all float values concatenated by a specified
     * separator.
     *
     * @param separator
     *            Separator string.
     * @param elements
     *            Float array.
     * @return a concatenated string.
     */
    public static String join(String separator, float... elements) {
        if (elements == null || elements.length == 0) {
            return ""; //$NON-NLS-1$
        }
        List<Number> list = new ArrayList<Number>(elements.length);
        for (Float elem : elements) {
            list.add(elem);
        }
        return join(separator, list);
    }

    /**
     * Returns a string with all double values concatenated by a specified
     * separator.
     *
     * @param separator
     *            Separator string.
     * @param elements
     *            Double array.
     * @return a concatenated string.
     */
    public static String join(String separator, double... elements) {
        if (elements == null || elements.length == 0) {
            return ""; //$NON-NLS-1$
        }
        List<Number> list = new ArrayList<Number>(elements.length);
        for (Double elem : elements) {
            list.add(elem);
        }
        return join(separator, list);
    }

    /**
     * Returns a formatted string of the specified number. All trailing zeroes
     * or decimal points will be stripped.
     *
     * @param number
     *            Number to convert to a string.
     * @return A formatted string.
     */
    public static String format(Number number) {
        String formatted = Double.toString(number.doubleValue()).replaceAll("\\.0+$", "") //$NON-NLS-1$ //$NON-NLS-2$
                .replaceAll("(\\.[0-9]*[1-9])0+$", "$1"); //$NON-NLS-1$ //$NON-NLS-2$
        return formatted;
    }

    /**
     * Returns a formatted string of the specified object.
     *
     * @param number
     *            Object to convert to a string.
     * @return A formatted string.
     */
    public static String format(Object obj) {
        if (obj instanceof Number) {
            return format((Number) obj);
        } else {
            return obj.toString();
        }
    }
}

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