演示死锁和解决死锁的方式

使用lock演示死锁

package lock的使用;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class 死锁 {
	public static void main(String[] args) {
		
		Lock lockA = new ReentrantLock();
		Lock lockB = new ReentrantLock();
		
		Thread t1 = new Thread() {
			@Override
			public void run() {
				System.out.println(this.getName()+"线程启动");
				System.out.println(this.getName()+"视图占用lockA");
				lockA.lock();
				System.out.println(this.getName()+"占用lockA成功");
				try {
					//执行5秒业务逻辑等待其他线程占用lockB
					Thread.sleep(5000);
					
					System.out.println(this.getName()+"视图占用lockB");
					lockB.lock();
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}finally {
					System.out.println(this.getName()+"线程结束");
					lockA.unlock();
				}
			}
		};
		t1.setName("T1");
		t1.start();
		
		Thread t2 = new Thread() {
			@Override
			public void run() {
				System.out.println(this.getName()+"线程启动");
				System.out.println(this.getName()+"视图占用lockB");
				lockB.lock();
				System.out.println(this.getName()+"占用lockB成功");
				try {
					//执行5秒业务逻辑等待其他线程占用lockA
					Thread.sleep(5000);
					
					System.out.println(this.getName()+"视图占用lockA");
					lockA.lock();
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}finally {
					System.out.println(this.getName()+"线程结束");
					lockB.unlock();
				}
			}
		};
		t2.setName("T2");
		t2.start();
	}
}

以下代码使用trylock()解决死锁问题

package lock的使用;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class 死锁 {
	public static void main(String[] args) {
		
		Lock lockA = new ReentrantLock();
		Lock lockB = new ReentrantLock();
		
		Thread t1 = new Thread() {
			@Override
			public void run() {
				//判断是否占用成功的boolean值
				boolean locked = false;
				System.out.println(this.getName()+"线程启动");
				System.out.println(this.getName()+"视图占用lockA");
				lockA.lock();
				System.out.println(this.getName()+"占用lockA成功");
				try {
					//执行5秒业务逻辑等待其他线程占用lockB
					Thread.sleep(5000);
					
					System.out.println(this.getName()+"视图占用lockB");
					//下边使用trylock()在T1线程已经占用lockA的情况下去占用lockB,trylock()在规定时间占用不到的情况下会放手从而避免死锁(29行,38行)
					//使用trylock()占用, 给两秒抢夺资源的时间
					locked = lockB.tryLock(2,TimeUnit.SECONDS);
					if(locked) {
						//如果占用成功则执行五秒的逻辑
						System.out.println(this.getName()+"线程占用lockB成功");
						Thread.sleep(5000);
						System.out.println(this.getName()+"线程占用lockB结束");
						lockB.unlock();
					}else {
						System.out.println(this.getName()+"线程花两秒时间占用lockB不成功");
					}
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}finally {
					System.out.println(this.getName()+"线程结束");
					lockA.unlock();
				}
			}
		};
		t1.setName("T1");
		t1.start();
		
		Thread t2 = new Thread() {
			@Override
			public void run() {
				//判断是否占用成功的boolean值
				boolean locked = false;
				
				System.out.println(this.getName()+"线程启动");
				System.out.println(this.getName()+"视图占用lockB");
				lockB.lock();
				System.out.println(this.getName()+"占用lockB成功");
				try {
					//执行5秒业务逻辑等待其他线程占用lockA
					Thread.sleep(5000);
					
					System.out.println(this.getName()+"视图占用lockA");
					//下边使用trylock()在T2线程已经占用lockB的情况下去占用lockA,trylock()在规定时间占用不到的情况下会放手从而避免死锁(68行,78行)
					//使用trylock()占用, 给两秒抢夺资源的时间
					locked = lockA.tryLock(2,TimeUnit.SECONDS);
					if(locked) {
						//如果占用成功则执行五秒的逻辑
						System.out.println(this.getName()+"线程占用lockA成功");
						Thread.sleep(5000);
						System.out.println(this.getName()+"线程占用lockA结束");
						//线程结束占用
						lockA.unlock();
					}else {
						System.out.println(this.getName()+"线程花两秒时间占用lockA不成功");
					}
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}finally {
					System.out.println(this.getName()+"线程结束");
					lockB.unlock();
				}
			}
		};
		t2.setName("T2");
		t2.start();
	}
}