java随机生成字符串工具类

package aA;

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

/**
 * 字符随机生成类
 */
public class RandomDemo {
    /**
     * 随机产生类型枚举
     */
    public static enum TYPE {
        /**小字符型*/
        LETTER,
        /**大写字符型*/
        CAPITAL,
        /**数字型*/
        NUMBER,
        /**大+小字符 型*/
        LETTER_CAPITAL,
        /**小字符+数字 型*/
        LETTER_NUMBER,
        /**大写字符+数字*/
        CAPITAL_NUMBER,
        /**大+小字符+数字 型*/
        LETTER_CAPITAL_NUMBER,
    }
    private static String[] lowercase = { "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o",
            "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z" };

    private static String[] capital = { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P",
            "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z" };

    private static String[] number = { "1", "2", "3", "4", "5", "6", "7", "8", "9", "0" };

    /**
     * 静态随机数
     */
    private static Random random = new Random();/**
     * 获取随机组合码
     * @param num 位数
     * @param type 类型
     * @type 
     * <br>小写字符型 LETTER,
     * <br>大写字符型 CAPITAL,
     * <br>数字型 NUMBER,
     * <br>大+小字符型 LETTER_CAPITAL,
     * <br>小字符+数字 型 LETTER_NUMBER,
     * <br>大字符+数字 型 CAPITAL_NUMBER,
     * <br>大+小字符+数字 型 LETTER_CAPITAL_NUMBER,
     */
    public static String getRandom(int num, TYPE type) {
        ArrayList<String> temp = new ArrayList<String>();
        StringBuffer code = new StringBuffer();
        switch (type) {
        case LETTER:
            temp.addAll(Arrays.asList(lowercase));
            break;
        case CAPITAL:
            temp.addAll(Arrays.asList(capital));
            break;
        case NUMBER:
            temp.addAll(Arrays.asList(number));
            break;
        case LETTER_CAPITAL:
            temp.addAll(Arrays.asList(lowercase));
            temp.addAll(Arrays.asList(capital));
            break;
        case LETTER_NUMBER:
            temp.addAll(Arrays.asList(lowercase));
            temp.addAll(Arrays.asList(number));
            break;
        case CAPITAL_NUMBER:
            temp.addAll(Arrays.asList(capital));
            temp.addAll(Arrays.asList(number));
            break;
        case LETTER_CAPITAL_NUMBER:
            temp.addAll(Arrays.asList(lowercase));
            temp.addAll(Arrays.asList(capital));
            temp.addAll(Arrays.asList(number));
            break;
        }
        for (int i = 0; i < num; i++) {
            code.append(temp.get(random.nextInt(temp.size())));
        }
        return code.toString();
    }
　　//测试

  　public static void main(String[] args) {
        System.out.println(RandomDemo.getRandom(10, RandomDemo.TYPE.LETTER_CAPITAL));
    }

}