使用CAS思想

这种方式就是会使得线程空跑，不会有线程的启动挂起

class TheadPrint implements Runnable{

    private AtomicInteger letter;

    private final int log;

    private final char print;

    public TheadPrint(AtomicInteger letter, int log, char print) {
        this.letter = letter;
        this.log = log;
        this.print = print;
    }

    @Override
    public void run() {
        int i=0;
        while (i<100){
            if(letter.get() % 2 == log){
                System.out.print(print);
                letter.incrementAndGet();
                i++;
            }
        }
    }
}

image.png

使用lock的方式

这种方式就是需要Park和UnPark线程

class TheadPrint1 implements Runnable{
    @Override
    public void run() {
        while (true){
            Application.lock.lock();
            if(Application.state % 2 == 0){
                System.out.println("A");
                Application.state ++;
            }
            Application.lock.unlock();
        }

    }
}
class TheadPrint2 implements Runnable{
    @Override
    public void run() {
        while (true){
            Application.lock.lock();
            if(Application.state % 2 == 1){
                System.out.println("B");
                Application.state ++;
            }
            Application.lock.unlock();
        }
    }
}

image.png

改进方式

class PrintThread implements Runnable{
    private Lock lock;
    private AtomicInteger signal ;
    private char[] printArray;
    public PrintThread(Lock lock ,AtomicInteger signal,char[] printArray) {
        this.lock = lock;
        this.signal = signal;
        this.printArray = printArray;
    }

    @Override
    public void run() {
        for(int i=0;i<100;i++){
            try {
                lock.lock();
                if(printArray != null && printArray.length > 0){
                    System.out.println(printArray[Math.abs(signal.get() % printArray.length)]);
                }
                signal.incrementAndGet();
            }finally {
                lock.unlock();
            }
        }
    }
}

总结

这两种方式都要涉及到公共资源的修改，必须有公共变量，一种是乐观模式一种是悲观模式