死锁：

//死锁
public class Synchronized {
    public static void main(String[] args) {
        MyThread thread = new MyThread();
        MyThread thread1 = new MyThread();
        thread.start();
        thread1.start();
    }
}
class MyThread extends Thread {
    static Object object1 = new Object();
    static Object object2 = new Object();
    @Override
    public void run() {
        while (true){
            test01();
            test02();
        }
    }
    public static void test01(){
        synchronized(object1){
            System.out.println("1");
            synchronized(object2){
                System.out.println("2");
            }
        }
    }
    public static void test02(){
        synchronized(object2){
            System.out.println("3");
            synchronized(object1){
                System.out.println("4");
            }
        }
    }
}

死锁原理：

生产消费者线程

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
//生产消费者线程
public class Synchronized {
    public static void main(String[] args) {
        //运输媒介
        List<Integer> storage = new ArrayList<>(100);
        new Thread(new Product(storage)).start();
        new Thread(new Consumer(storage)).start();
    }
}
class Product implements Runnable {
    private List<Integer> storage;
    public Product(List<Integer> storage) {
        this.storage = storage;
    }
    @Override
    public void run() {
        while (true) {
            synchronized (storage) {
                if (storage.size() < 10) {
                    storage.add(1);
                    System.out.println("生产一个");
                } else {
                    try {
                        //唤醒所有在使用storage对象的线程
                        storage.notifyAll();
                        //让出当前使用storage对象并抢占了锁的线程，总之就是让出当前线程占用的锁
                        storage.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}
class Consumer implements Runnable {
    List<Integer> storage;
    public Consumer(List<Integer> storage) {
        this.storage = storage;
    }
    @Override
    public void run() {
        while (true) {
            synchronized (storage) {
                if (storage.size() > 0) {
                    Iterator it = storage.iterator();
                    while (it.hasNext()){
                        System.out.println("消费："+it.next());
                        it.remove();
                    }
                }else {
                    try {
                        storage.notifyAll();
                        storage.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}

例：奇数偶数交换输出

import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;
import java.util.ArrayList;
import java.util.List;
public class HomeWork {
    public static void main(String[] args) {
        List<Integer> list = new ArrayList<>(1);
        Integer i = 1;
        list.add(i);
        new Thread(new Even(list)).start();
        new Thread(new Odd(list)).start();
    }
}
class Even implements Runnable {
    private List<Integer> list;
    public Even(List<Integer> list) {
        this.list = list;
    }
    @Override
    public void run() {
        while (true) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (list) {
                if (list.get(0) % 2 != 0) {
                    System.out.println("奇数："+list.get(0));
                    list.set(0,list.get(0)+1);
                }else {
                    list.notifyAll();
                    try {
                        list.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}
class Odd implements Runnable {
    private List<Integer> list;
    public Odd(List<Integer> list) {
        this.list = list;
    }
    @Override
    public void run() {
        while (true) {
            synchronized (list) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                if (list.get(0) % 2 == 0) {
                    System.out.println("偶数："+list.get(0));
                    list.set(0,list.get(0)+1);
                }else {
                    list.notifyAll();
                    try {
                        list.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}