华为OJ初级题中多线程

问题描述：有4个线程和1个公共的字符数组。线程1的功能就是向数组输出A，线程2的功能就是向字符输出B，线程3的功能就是向数组输出C，线程4的功能就是向数组输出D。要求按顺序向数组赋值ABCDABCDABCD，ABCD的个数由线程函数1的参数指定。

我采用java实现代码如下：

public class IterPrint {

public static void main(String[] args) {

Scanner scanner=new Scanner(System.in);
int num=scanner.nextInt();
scanner.close();
MyThread thr1 = new MyThread('A',num);
MyThread thr2 = new MyThread('B');
MyThread thr3 = new MyThread('C');
MyThread thr4 = new MyThread('D');
new Thread(thr1).start();
new Thread(thr2).start();
new Thread(thr3).start();
new Thread(thr4).start();
}

}

class MyThread implements Runnable {
public final char ch;// 负责打印的字符
public static char[] chs =null;
public static int index;
public static int iterNum = 3;//默认值
public static char flag = 'A';
public static Object lock = new Object();

// 负责打印的字符，构造函数传入之后，不再修改
public MyThread(char ch) {
super();
this.ch = ch;
}

// 负责打印的字符，构造函数传入之后，不再修改
public MyThread(char ch, int num) {
super();
this.ch = ch;
MyThread.iterNum = num;
}

@Override
public void run() {
for (int i = 0; i < iterNum; i++) {

printWr(ch);

}
}

public void printWr(char ch) {
// 没有分到，则循环等待
while (ch != flag||(flag!='A'&&chs==null));

synchronized (lock) {
if(flag=='A'&&chs==null)
chs=new char[iterNum*4];

chs[index] = ch;
System.out.print(chs[index]);
index++;
flag += 1;// +=自动完成flag强制类型转化

if (flag == 'E')
flag = 'A';

}
}

}