1. 使用LockSupport.park()

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.LockSupport;
public class Main {
    static Thread t1 = null;
    static Thread t2 = null;
    public static void main(String[] args) throws InterruptedException {
        char[] array1 = "123456789".toCharArray();
        char[] array2 = "ABCDEFGHI".toCharArray();
        t1 = new Thread(()->{
            for (int i = 0; i < array1.length; i++) {
                System.out.println(array1[i]);
                LockSupport.unpark(t2);     //让t2执行
                LockSupport.park();         //自身停止
            }
        },"t1");
        t2 = new Thread(()->{
            for (int i = 0; i < array2.length; i++) {
                LockSupport.park();         //自身停止
                System.out.println(array2[i]);
                LockSupport.unpark(t1);     //让t1执行
            }
        },"t2");
        t1.start();
        t2.start();
    }
}

2. 类似cas实现

public class Mian1 {
    private enum ReadAndRun{ T1, T2 }
    static volatile ReadAndRun readAndRun = ReadAndRun.T1;
    public static void main(String[] args) {
        char[] array1 = "123456789".toCharArray();
        char[] array2 = "ABCDEFGHI".toCharArray();
        new Thread(()->{
            for (char c: array1) {
                while( readAndRun != ReadAndRun.T1 ){ }
                System.out.println(c);
                readAndRun = ReadAndRun.T2;
            }
        },"t1").start();
        new Thread(()->{
            for (char c: array2) {
                while( readAndRun != ReadAndRun.T2 ){ }
                System.out.println(c);
                readAndRun = ReadAndRun.T1;
            }
        },"t2").start();
    }
}