一、兩執行緒交替列印數字和字母

要求控制檯中輸出的內容為 A1B2C3D4
這應該是多執行緒面試題中推簡單的筆試題了吧；

1.Object. notify()和Object.wait()實現；

 private void init (){
       char[] c = new char[26];
        int[] num = new int[26];
        for (int i = 0; i < 26; i++) {
            c[i ] = (char) (i+65);
            num[i ] = i ;
        }
        PrintChar printChar = new PrintChar(c);
        printChar.start();
        PrintNum printNum = new PrintNum(num);
        printNum.start();
    }

    class PrintChar extends Thread {
        private char[] c;
        public PrintChar(char[] c) {
            this.c = c;
        }
        @Override
        public void run() {
            super.run();
            for (char s : c) {
                synchronized (cLock) {
                    cLock.notify();
                    try {
                        cLock.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(s);
                }

            }
        }
    }

    class PrintNum extends Thread {
        private int[] num;

        public PrintNum(int[] num) {
            this.num = num;
        }

        @Override
        public void run() {
            super.run();
            for (int i : num) {
                synchronized (cLock) {
                    cLock.notify();
                    try {
                        cLock.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(i);
                }
            }
        }
    }
 

2. ReentrantLock和Condition 實現

private void init (){
         Lock lock = new ReentrantLock();
        Condition cCondition = lock.newCondition();
        Condition nCondition = lock.newCondition();
        char[] c = new char[26];
        int[] num = new int[26];
        for (int i = 0; i < 26; i++) {
            c[i ] = (char) (i+65);
            num[i ] = i ;
        }
        PrintChar printChar = new PrintChar(c, lock, cCondition, nCondition);
        printChar.start();
        PrintNum printNum = new PrintNum(num, lock, cCondition, nCondition);
        printNum.start();
    }
 class PrintChar extends Thread {
        private char[] c;
        private Condition cCondition, nCondition;
        private Lock lock;

        public PrintChar(char[] c, Lock lock, Condition cCondition, Condition nCondition) {
            this.c = c;
            this.nCondition = nCondition;
            this.cCondition = cCondition;
            this.lock = lock;
        }

        @Override
        public void run() {
            super.run();
            for (char s : c) {
                System.out.println(s);
                lock.lock();
                try {
                    nCondition.signal();
                    cCondition.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {
                    lock.unlock();
                }
            }

            try {
                lock.lock();
                nCondition.signal();
            }finally {
                lock.unlock();
            }
        }
    }
}

class PrintNum extends Thread {
    private int[] num;
    private Condition cCondition, nCondition;
    private Lock lock;

    public PrintNum(int[] num, Lock lock, Condition cCondition, Condition nCondition) {
        this.num = num;
        this.nCondition = nCondition;
        this.cCondition = cCondition;
        this.lock = lock;
    }

    @Override
    public void run() {
        super.run();
        for (int i : num) {
            System.out.println(i);
            try {
                lock.lock();
                cCondition.signal();
                nCondition.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }
        }
        try {
            lock.lock();
            nCondition.signal();
        }finally {
            lock.unlock();
        }
    }
 

3.LockSupport實現

public init() {
        char[] c = new char[26];
        int[] num = new int[26];
        for (int i = 0; i < 26; i++) {
            c[i ] = (char) (i+65);
            num[i] = i ;
        }
        PrintChar printChar = new PrintChar(c);
        PrintNum printNum = new PrintNum(num);
        printChar.setThread(printNum);
        printNum.setThread(printChar);
        printChar.start();
        printNum.start();
    }

  class PrintChar extends Thread {
        private char[] c;
        private Thread thread;
        public void setThread(Thread thread) {
            this.thread = thread;
        }
        public PrintChar(char[] c) {
            this.c = c;
        }

        @Override
        public void run() {
            super.run();
            for (char s : c) {
                System.out.println(s);
                LockSupport.unpark(this.thread);
                LockSupport.park();
            }
            LockSupport.unpark(this.thread);
        }
    }

    class PrintNum extends Thread {
        private int[] num;
        private Thread thread;
        public void setThread(Thread thread) {
            this.thread = thread;
        }

        public PrintNum(int[] num) {
            this.num = num;
        }

        @Override
        public void run() {
            super.run();
            LockSupport.park();
            for (int i : num) {
                System.out.println(i);
                LockSupport.unpark(this.thread);
                LockSupport.park();
            }
            LockSupport.unpark(this.thread);
        }
    }
 

4.阻塞佇列實現

public init() {
        char[] c = new char[26];
        int[] num = new int[26];
        for (int i = 0; i < 26; i++) {
            c[i ] = (char) (i+65);
            num[i] = i ;
        }
        BlockingQueue<String> queue = new ArrayBlockingQueue<>(2);
        PrintChar printChar = new PrintChar(c,queue);
        PrintNum printNum = new PrintNum(num,queue);
        printChar.start();
        printNum.start();
    }

 class PrintChar extends Thread {
        private char[] c;
        private BlockingQueue<String> queue;

        public PrintChar(char[] c,BlockingQueue<String> queue) {
            this.c = c;
            this.queue = queue;
        }

        @Override
        public void run() {
            super.run();
            for (char s : c) {
                try {
                    queue.put("--");
                    queue.put("--");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(s);
            }
        }
    }

    class PrintNum extends Thread {
        private int[] num;
        private  BlockingQueue<String> queue;
        public PrintNum(int[] num,BlockingQueue<String> queue) {
            this.num = num;
            this.queue=queue;
        }
        @Override
        public void run() {
            super.run();
            for (int i : num) {
                try {
                    queue.take();
                    queue.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(i);
            }
        }
    }