用Java写一个26字母和0-9数字 不同长度组合的输出，输出全部的时间不能超过2个小时。需要用多线程录

直接上代码

public class MyThread extends Thread{
    char[] word = new char[]{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'g', 'k', 'l'
            , 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
            'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
    int mark;
    public MyThread(int mark) {
        this.mark = mark;
    }
    public void loop(int count){
        char [] newWord = new char[6];
        for (int i = mark;i <= count;i++) {
            newWord[0] = word[i];
            for (int j = 0;j <= 35;j++) {
                newWord[1] = word[j];
                for (int k = 0;k <= 35;k++) {
                    newWord[2] = word[k];
                    for (int l = 0;l <= 35;l++) {
                        newWord[3] = word[l];
                        for (int m = 0;m <= 35;m++) {
                            newWord[4] = word[m];
                            for (int n = 0;n <= 35;n++) {
                                newWord[5] = word[n];
                                System.out.println(newWord);
                            }
                        }

                    }
                }
            }

        }
    }
    @Override
    public void run() {
        loop(mark);
    }

    public static void main(String[] args) {
        for (int i = 0;i<=35;i++){
            MyThread MyThread = new MyThread(i);
            MyThread.start();
        }

    }

}