Java Collection to String collectionToString(Collection collection)

Description

Returns a collection of Strings as a comma-delimitted list of strings.

License

Open Source License

Return

a String representing the Collection.

Declaration

public static String collectionToString(Collection<String> collection) 

Method Source Code

//package com.java2s;
/**/*w w w  . j  a  v  a  2s .c  om*/
 * <p>
 * Simple utility class for String operations useful across the framework.
 * <p/>
 * <p>
 * Some methods in this class were copied from the Spring Framework so we didn't
 * have to re-invent the wheel, and in these cases, we have retained all
 * license, copyright and author information.
 *
 * @since 0.9
 */

import java.util.*;

public class Main {
    /**
     * Constant representing the empty string, equal to &quot;&quot;
     */
    public static final String EMPTY_STRING = "";

    /**
     * Returns a collection of Strings as a comma-delimitted list of strings.
     *
     * @return a String representing the Collection.
     */
    public static String collectionToString(Collection<String> collection) {
        if (collection == null || collection.isEmpty()) {
            return "";
        }
        StringBuilder buf = new StringBuilder();
        String delim = "";
        for (String element : collection) {
            buf.append(delim);
            buf.append(element);
            delim = ",";
        }
        return buf.toString();
    }

    /**
     * Returns the specified array as a comma-delimited (',') string.
     *
     * @param array the array whose contents will be converted to a string.
     * @return the array's contents as a comma-delimited (',') string.
     * @since 1.0
     */
    public static String toString(Object[] array) {
        return toDelimitedString(array, ",");
    }

    /**
     * Returns the array's contents as a string, with each element delimited by
     * the specified {@code delimiter} argument. Useful for {@code toString()}
     * implementations and log messages.
     *
     * @param array the array whose contents will be converted to a string
     * @param delimiter the delimiter to use between each element
     * @return a single string, delimited by the specified {@code delimiter}.
     * @since 1.0
     */
    public static String toDelimitedString(Object[] array, String delimiter) {
        if (array == null || array.length == 0) {
            return EMPTY_STRING;
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < array.length; i++) {
            if (i > 0) {
                sb.append(delimiter);
            }
            sb.append(array[i]);
        }
        return sb.toString();
    }

    /**
     * Returns the collection's contents as a string, with each element
     * delimited by the specified {@code delimiter} argument. Useful for
     * {@code toString()} implementations and log messages.
     *
     * @param c the collection whose contents will be converted to a string
     * @param delimiter the delimiter to use between each element
     * @return a single string, delimited by the specified {@code delimiter}.
     * @since 1.2
     */
    public static String toDelimitedString(Collection c, String delimiter) {
        if (c == null || c.isEmpty()) {
            return EMPTY_STRING;
        }
        return join(c.iterator(), delimiter);
    }

    /**
     * Joins the elements of the provided {@code Iterator} into a single String
     * containing the provided elements.</p>
     * <p/>
     * No delimiter is added before or after the list. A {@code null} separator
     * is the same as an empty String ("").</p>
     * <p/>
     * Copied from Commons Lang, version 3 (r1138702).</p>
     *
     * @param iterator the {@code Iterator} of values to join together, may be
     * null
     * @param separator the separator character to use, null treated as ""
     * @return the joined String, {@code null} if null iterator input
     * @since 1.2
     */
    public static String join(Iterator<?> iterator, String separator) {
        final String empty = "";

        // handle null, zero and one elements before building a buffer
        if (iterator == null) {
            return null;
        }
        if (!iterator.hasNext()) {
            return empty;
        }
        Object first = iterator.next();
        if (!iterator.hasNext()) {
            return first == null ? empty : first.toString();
        }

        // two or more elements
        StringBuilder buf = new StringBuilder(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();
    }
}

Related

1. collectionToString(Collection list)
2. collectionToString(Collection collection, String prefix)
3. collectionToString(Collection