2020 阿里巴巴機試之線程順序執行

 

上代碼：

import java.util.ArrayList;
import java.util.List;

public class ThreadSortsPrint {

    private static volatile char c = 'C';

    private static List<Character> list = new ArrayList<>(1000);

    public static void main(String[] args) throws InterruptedException {
        System.out.println(Math.round(-1.5));

        Thread t1 = new Thread(() -> {

            int count = 0;
            while (count <100) {
                synchronized (ThreadSortsPrint.class) {
                    if (c =='C') {
                        System.out.print("A");
                        c = 'A';
                        list.add(c);
                        count++;
                        ThreadSortsPrint.class.notifyAll();
                    }else {
                        try {
                            ThreadSortsPrint.class.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        });

        Thread t2 = new Thread(() -> {
            int count = 0;
            while (count <100) {
                synchronized (ThreadSortsPrint.class) {
                    if (c == 'A') {
                        System.out.print("B");
                        c = 'B';
                        list.add(c);
                        count++;
                        ThreadSortsPrint.class.notifyAll();
                    }else {
                        try {
                            ThreadSortsPrint.class.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        });

        Thread t3 = new Thread(() -> {
            int count = 0;
            while (count <100) {
                synchronized (ThreadSortsPrint.class) {
                    if (c =='B') {
                        System.out.print("C");
                        c = 'C';
                        list.add(c);
                        count++;
                        ThreadSortsPrint.class.notifyAll();
                    }else {
                        try {
                            ThreadSortsPrint.class.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        });

        t1.start();
        t2.start();
        t3.start();

        t1.join();
        t2.join();
        t3.join();


        StringBuilder stringBuilder = new StringBuilder();
        for(Character c:list){
            System.out.print(c);
            stringBuilder.append(c);
        }

        System.out.println();
        System.out.println(stringBuilder.length());
    }


}

輸出結果：