锁

重入锁

Condition

读写锁

适用于读多写少场景

死锁

final Object lockA = new Object();
        final Object lockB = new Object();

        new Thread() {
            @Override
            public void run() {
                synchronized (lockB) {
                    System.out.println("获取锁B");
                    try {
                        sleep(3000L);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    synchronized (lockA) {
                        System.out.print("t1");
                    }
                }
            }
        }.start();


        new Thread() {
            @Override
            public void run() {
                synchronized (lockA) {
                    System.out.println("获取锁A");
                    try {
                        sleep(3000L);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    synchronized (lockB) {
                        System.out.print("t2");
                    }
                }
            }
        }.start();