请教多线程基础问题。

public class TaskThreadDemo {

      public static void main(String[] args) {

            //创建任务

            Runnable printA = new PrintChar('a', 10000);

            Runnable printB = new PrintChar('b', 100);

            Runnable print100 = new PrintNum(100);

            //创建线程

            Thread thread1 = new Thread(printA);

            Thread thread2 = new Thread(printB);

            Thread thread3 = new Thread(print100);

            //启动线程

            thread1.start();

            thread2.start();

            thread3.start();

      }

}



class PrintChar implements Runnable{

      private char charToPrint;

      private int times;

      public PrintChar(char c, int t){

            charToPrint = c;

            times = t;

      }

      @Override

      public void run() {

            for (int i = 0; i < times; i++) {

                  System.out.print(charToPrint);

            }

      }

}



class PrintNum implements Runnable{

      private int lastNum;

      public PrintNum(int n){

            lastNum = n;

      }

      @Override

      public void run() {

            for (int i = 0; i < lastNum; i++) {

                  System.out.print(" " + i);

            }

      }

}