Java Random生成序列号例子

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import java.util.Random;

public class SidGenerator {

        /**
         * 序列号格式:16
         *
         * @return
         */
        public static String nextVal() {
                return randomCode(16);
        }

        /**
         * 序列号格式:16
         *
         * @return
         */
        public static String nextValNum() {
                return randomCodeNum(16);
        }

        /**
         * 序列号格式:16
         *
         * @return
         */
        public static String nextValNum(int len) {
                return randomCodeNum(len);
        }

        public static String randomCode(int length) {
                Random randGen = null;
                char[] numbersAndLetters = null;
                Object initLock = new Object();
                if (randGen == null) {
                        synchronized (initLock) {
                                if (randGen == null) {
                                        randGen = new Random();
                                        numbersAndLetters = ("0123456789abcdefghijklmnopqrstuvwxyz"
                                                        + "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
                                }
                        }
                }
                char[] randBuffer = new char[length];
                for (int i = 0; i < randBuffer.length; i++) {
                        randBuffer[i] = numbersAndLetters[randGen.nextInt(71)];
                }
                return new String(randBuffer);
        }

        public static String randomCodeNum(int length) {
                Random randGen = null;
                char[] numbersAndLetters = null;
                Object initLock = new Object();
                if (randGen == null) {
                        synchronized (initLock) {
                                if (randGen == null) {
                                        randGen = new Random();
                                        numbersAndLetters = ("01234567890123456789").toCharArray();
                                }
                        }
                }
                char[] randBuffer = new char[length];
                for (int i = 0; i < randBuffer.length; i++) {
                        randBuffer[i] = numbersAndLetters[randGen.nextInt(19)];
                }
                return new String(randBuffer);
        }

        public static void main(String[] args) {
                System.out.println(nextVal());
                System.out.println(nextValNum());
                System.out.println(nextValNum());
                System.out.println(nextValNum());
                System.out.println(nextValNum());
                System.out.println(nextValNum());
                System.out.println(nextValNum());
                System.out.println(nextValNum());
                System.out.println(nextValNum());
                System.out.println(nextValNum());

        }
}