随机生成字符串，并进行排序的方法

// 随机添加String.
public void Test3() {
List<String> stringlist = new ArrayList<String>();
String str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

    Random random = new Random();
    Random random2 = new Random();

    for (int i = 0; i < 5; i++) {
        StringBuffer sb = new StringBuffer();
        int length;
        do {                
             length = random2.nextInt(5);
        } while (length==0);

        for (int j = 0; j < length; j++) {
            int number = random.nextInt(62);
            sb = sb.append(str.charAt(number));
        }
        if (!stringlist.contains(sb)) {
            String print = sb.toString();
            System.out.println("添加了：" + print);
            stringlist.add(print);
        }
    }
    System.out.println(stringlist);
    System.out.println("-----排序后：-----");
    java.util.Collections.sort(stringlist);
    for (String string : stringlist) {
        System.out.println(string);
    }

}