Java Random String generateRandomString(final int minCharLen, final int maxCharLen)

Description

generate Random String

License

Open Source License

Declaration

public static String generateRandomString(final int minCharLen, final int maxCharLen) 

Method Source Code

//package com.java2s;
/**//from   w  w  w. j a  va  2  s . co  m
 * The MIT License (MIT)
 *
 * Copyright (c) 2016 netirc.org development team
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

import java.util.Random;

public class Main {
    private static String symbols;

    public static String generateRandomString(final int minCharLen, final int maxCharLen) {
        if (minCharLen > maxCharLen) {
            throw new IllegalArgumentException(
                    "Maximum Character Length must be larger than the Minimum Character Length");
        }

        StringBuilder builder = new StringBuilder();
        generateCharacterList();
        int len = (int) (Math.random() * (minCharLen - maxCharLen)) + minCharLen;

        Random r = new Random();
        final int randomMax = symbols.length();

        for (int i = 0; i < len; i++) {
            builder.append(symbols.charAt(r.nextInt(randomMax)));
        }

        return builder.toString();
    }

    protected static void generateCharacterList() {
        if (symbols != null) {
            return;
        }

        StringBuilder tmp = new StringBuilder();

        for (char ch = '0'; ch <= '9'; ++ch) {
            tmp.append(ch);
        }
        for (char ch = 'a'; ch <= 'z'; ++ch) {
            tmp.append(ch);
        }
        for (char ch = 'A'; ch <= 'Z'; ++ch) {
            tmp.append(ch);
        }

        symbols = tmp.toString();
    }
}

Related

1. generateRandomString()
2. generateRandomString()
3. generateRandomString()
4. generateRandomString()
5. generateRandomString()
6. generateRandomString(final String pattern)
7. generateRandomString(int count)
8. generateRandomString(int len)
9. generateRandomString(int length)