Java用三个线程按顺序循环打印 abc 三个字母,比如 abcabcabc。

Myth丶恋晨 2022-05-24 13:40 144阅读 0赞

这是一道经典的Java多线程面试题。自己写了一种较为巧妙的方法：

package JavaDay5_27;
    
    import java.util.Collections;
    
    /**
     * @author myvina@qq.com
     * @date 18-5-27  下午8:00
     */
    
    public class Demo1 {
        public static void main(String[] args) {
            Demo1 demo1 = new Demo1();
            PrintLetter printLetter = demo1.new PrintLetter();
            new Thread(demo1.new PrintThread(printLetter, 'B')).start();
            new Thread(demo1.new PrintThread(printLetter, 'A')).start();
            new Thread(demo1.new PrintThread(printLetter, 'C')).start();
    //        Collections.synchronizedList()
        }
    
        private class PrintLetter {
            private char letter = 'A';
    
            public char getLetter() {
                return letter;
            }
    
            public void print() {
                System.out.print(letter);
                if('C' == letter) {
                    System.out.println();
                }
            }
    
            public void nextLetter() {
                switch (letter) {
                    case 'A': {
                        letter = 'B';
                        break;
                    }
                    case 'B': {
                        letter = 'C';
                        break;
                    }
                    case 'C': {
                        letter = 'A';
                        break;
                    }
                }
            }
        }
    
        private class PrintThread implements Runnable {
            private PrintLetter printLetter;
            private char letter;
    
            public PrintThread(PrintLetter printLetter, char letter) {
                this.printLetter = printLetter;
                this.letter = letter;
            }
    
            @Override
            public void run() {
                for(int i = 0; i < 10; i++) {
                    synchronized (printLetter) {
                        while(letter != printLetter.getLetter()) {
                            try {
                                printLetter.wait();
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                        printLetter.print();
                        printLetter.nextLetter();
                        printLetter.notifyAll();
                    } 
                }
            }
        }
    }

运行结果为：

![70][]

[70]: /images/20220524/abc0c3d64e7a4ee6b1b7d0c851c9b848.png