UUID.java

/*******************************************************************************
 * Copyright (c) 2012-2017 Codenvy, S.A.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   Codenvy, S.A. - initial API and implementation
 *******************************************************************************/
package org.eclipse.che.ide.util;

/**
 * Generate a random UUID.
 *
 * @author Artem Zatsarynnyi
 */
public class UUID {
    private static final char[] CHARS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".toCharArray();

    /**
     * Generate a random uuid of the specified length.
     * Example: uuid(15) returns "VcydxgltxrVZSTV"
     *
     * @param len
     *         the desired number of characters
     */
    public static String uuid(int len) {
        return uuid(len, CHARS.length);
    }

    /**
     * Generate a random uuid of the specified length, and radix.
     * Examples:
     * <ul>
     * <li>uuid(8, 2) returns "01001010" (8 character ID, base=2)
     * <li>uuid(8, 10) returns "47473046" (8 character ID, base=10)
     * <li>uuid(8, 16) returns "098F4D35" (8 character ID, base=16)
     * </ul>
     *
     * @param len
     *         the desired number of characters
     * @param radix
     *         the number of allowable values for each character (must be <= 62)
     */
    public static String uuid(int len, int radix) {
        if (radix > CHARS.length) {
            throw new IllegalArgumentException();
        }
        char[] uuid = new char[len];
        // Compact form
        for (int i = 0; i < len; i++) {
            uuid[i] = CHARS[(int)(Math.random() * radix)];
        }
        return new String(uuid);
    }

    /**
     * Generate a RFC4122, version 4 ID.
     * Example: "92329D39-6F5C-4520-ABFC-AAB64544E172"
     */
    public static String uuid() {
        char[] uuid = new char[36];
        int r;

        // rfc4122 requires these characters
        uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';
        uuid[14] = '4';

        // Fill in random data.  At i==19 set the high bits of clock sequence as
        // per rfc4122, sec. 4.1.5
        for (int i = 0; i < 36; i++) {
            if (uuid[i] == 0) {
                r = (int)(Math.random() * 16);
                uuid[i] = CHARS[(i == 19) ? (r & 0x3) | 0x8 : r & 0xf];
            }
        }
        return new String(uuid);
    }

}