实现打印26个数字和26个字母交替打印

0、面试题

实现：第一个线程从1到26，第二个线程从A到Z，然后要让这两个线程做到同时运行，交替输出，顺序打印。

输出结果：1A2B3C4D5E6F7G8H9I10J11K12L13M14N15O16P17Q18R19S20T21U22V23W24X25Y26Z

你有哪些玩法？

1、LockSupport

public class LockSupportDemo {
    
    static Thread t1 = null, t2 = null;

    public static void main(String[] args) {
        String[] nums = new String[]{
                "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26"
        };
        String[] letters = new String[]{
                "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        };

        t1 = new Thread(() -> {
            for (String num : nums) {
                System.out.print(num);
                LockSupport.unpark(t2);//唤醒 t2
                LockSupport.park();// t1 阻塞
            }
        }, "T1");

        t2 = new Thread(() -> {
            for (String letter : letters) {
                LockSupport.park();// t2 阻塞
                System.out.print(letter);
                LockSupport.unpark(t1);//唤醒 t1
            }
        }, "T2");

        t1.start();
        t2.start();
    }
}

2、synchronized+wait+notify

public class WaitNotifyDemo {

    static Thread t1 = null, t2 = null;


    public static void main(String[] args) {

        final Object o = new Object();

        String[] nums = new String[]{
                "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26"
        };
        String[] letters = new String[]{
                "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        };

        t1 = new Thread(() -> {
            synchronized (o) {
                try {
                    for (String num : nums) {
                        System.out.print(num);
                        o.notify();
                        o.wait(); //阻塞 t1
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                o.notify();//必须，否则无法停止程序
            }
        }, "T1");

        t2 = new Thread(() -> {
            synchronized (o) {
                try {
                    for (String letter : letters) {
                        System.out.print(letter);
                        o.notify();
                        o.wait(); //阻塞 t2
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                o.notify(); //必须，否则无法停止程序
            }
        }, "T2");

        t1.start();
        t2.start();
    }
}

3、ReentrantLock + 1个Condition

public class LockConditionDemo {

    static Thread t1 = null, t2 = null;

    public static void main(String[] args) {

        String[] nums = new String[]{
                "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26"
        };
        String[] letters = new String[]{
                "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        };

        ReentrantLock lock = new ReentrantLock();

        Condition condition = lock.newCondition();

        t1 = new Thread(() -> {
            lock.lock();
            try {
                for (String num : nums) {
                    System.out.print(num);
                    condition.signal();
                    condition.await();
                }
                condition.signal();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "T1");

        t2 = new Thread(() -> {

            lock.lock();
            try {
                for (String letter : letters) {
                    System.out.print(letter);
                    condition.signal();
                    condition.await();
                }
                condition.signal();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "T2");

        t1.start();
        t2.start();
    }
}

4、ReentrantLock + 2个Condition

public class LockConditionDemo2 {

    static Thread t1 = null, t2 = null;

    public static void main(String[] args) {

        String[] nums = new String[]{
                "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26"
        };
        String[] letters = new String[]{
                "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        };

        ReentrantLock lock = new ReentrantLock();

        Condition conditionT1 = lock.newCondition();
        Condition conditionT2 = lock.newCondition();

        t1 = new Thread(() -> {
            lock.lock();
            try {
                for (String num : nums) {
                    System.out.print(num);
                    conditionT2.signal();
                    conditionT1.await();
                }
                conditionT2.signal();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "T1");

        t2 = new Thread(() -> {

            lock.lock();
            try {
                for (String letter : letters) {
                    System.out.print(letter);
                    conditionT1.signal();
                    conditionT2.await();
                }
                conditionT1.signal();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "T2");

        t1.start();
        t2.start();
    }
}

5、自定义CAS实现

public class CASDemo {

    enum ReadyToRun {T1, T2}

    static volatile ReadyToRun r = ReadyToRun.T1;

    static Thread t1 = null, t2 = null;

    public static void main(String[] args) {
        String[] nums = new String[]{
                "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26"
        };
        String[] letters = new String[]{
                "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        };

        t1 = new Thread(() -> {
            for (String num : nums) {
                while (r != ReadyToRun.T1) {
                }
                System.out.print(num);
                r = ReadyToRun.T2;
            }
        }, "T1");

        t2 = new Thread(() -> {
            for (String letter : letters) {
                while (r != ReadyToRun.T2) {
                }
                System.out.print(letter);
                r = ReadyToRun.T1;
            }
        }, "T2");

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

    }

}

6、Semaphore

public class SemaphoreDemo {

    static Thread t1 = null, t2 = null;

    private static Semaphore semaphore1 = new Semaphore(1);
    private static Semaphore semaphore2 = new Semaphore(0);

    public static void main(String[] args) {
        String[] nums = new String[]{
                "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26"
        };
        String[] letters = new String[]{
                "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        };

        t1 = new Thread(() -> {
            try {
                for (String num : nums) {

                    semaphore1.acquire();
                    System.out.print(num);
                    semaphore2.release();

                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "T1");

        t2 = new Thread(() -> {
            try {
                for (String letter : letters) {
                    semaphore2.acquire();
                    System.out.print(letter);
                    semaphore1.release();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "T2");

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

    }

}

7、BlockingQueue

public class BlockingQueueDemo {

    static BlockingQueue<String> queue1 = new ArrayBlockingQueue<>(1);
    static BlockingQueue<String> queue2 = new ArrayBlockingQueue<>(1);

    static Thread t1 = null, t2 = null;

    public static void main(String[] args) {

        String[] nums = new String[]{
                "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26"
        };
        String[] letters = new String[]{
                "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        };

        t1 = new Thread(() -> {
            try {
                for (String num : nums) {
                    System.out.print(num);
                    queue1.put("ok");
                    queue2.take();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "T1");

        t2 = new Thread(() -> {
            try {
                for (String letter : letters) {
                    queue1.take();
                    System.out.print(letter);
                    queue2.put("ok");
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "T2");

        t1.start();
        t2.start();
        
    }

}

8、TransferQueue

public class TransferQueueDemo {

    static Thread t1 = null, t2 = null;

    public static void main(String[] args) {
        String[] nums = new String[]{
                "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26"
        };
        String[] letters = new String[]{
                "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"
        };

        TransferQueue<String> queue = new LinkedTransferQueue<>();

        t1 = new Thread(() -> {
            try {
                for (String num : nums) {
                    queue.transfer(num);
                    System.out.print(queue.take());
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "T1");

        t2 = new Thread(() -> {
            try {
                for (String letter : letters) {
                    System.out.print(queue.take());
                    queue.transfer(letter);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "T2");

        t1.start();
        t2.start();
    }
}
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