死锁简要概述 java

死锁：两个或两个以上的线程在执行的过程中，由于竞争资源或者彼此等待彼此而造成彼此等待彼此，线程不再往下执行。
根据以上示例图构建连个死锁程序
（1）DeadLock

package com.high.concurrency.currency02.eat; public class DeadLock extends Thread {private String first; private String second; public DeadLock(String name, String first, String second) { super(name); this.first = first; this.second = second; } @Override publicvoid run() { synchronized (first) { try { System.out.println(this.getName() + " ...synchronized:===> 【first】" + first); Thread.sleep(1000L); synchronized (second) { System.out.println(this.getName() + " ...synchronized:===>【second】 " + second); } } catch (InterruptedException e) {} } } public static void main(String[] args) throws InterruptedException { String lockA = "lockA"; String lockB = "lockB"; DeadLock t1 = new DeadLock("t1", lockA, lockB); DeadLock t2 = new DeadLock("t2", lockB, lockA); t1.start(); t2.start(); t1.join(); t2.join(); } }

（2）PhilosopherEating package com.high.concurrency.currency02.eat; public class PhilosopherEating extends Thread { protected Object tool; static Object fork1 = new Object(); static Object fork2 = new Object(); public PhilosopherEating(Object obj) { this.tool = obj; if(tool == fork1) { this.setName("哲学家A"); } if (tool == fork2) { this.setName("哲学家B"); } }@Override public void run() { if(tool == fork1) { synchronized (fork1) { try { Thread.sleep(500); } catch (Exception e) { e.printStackTrace(); } synchronized (fork2) { System.out.println("哲学家A开始吃饭了"); } } }if (tool == fork2) { synchronized (fork2) { try { Thread.sleep(500); } catch (InterruptedException e) { e.printStackTrace(); }synchronized (fork1) { System.out.println("哲学家B开始吃饭了"); } } } }public static void main(String[] args) throws InterruptedException { PhilosopherEating philosonpherA = new PhilosopherEating(fork1); PhilosopherEating philosonpherB = new PhilosopherEating(fork2); philosonpherA.start(); philosonpherB.start(); Thread.sleep(1000); }}

上述程序都体现一个特点：存在两个线程，出现我使用这当前的资源，申请对方正在使用的资源，而对方尚未释放该资源导致线程阻塞。
查找线程死锁的办法：jps + jstack
首先在终端输入jps，查找到对应的死锁进程号：