亚洲无码Av在线综合6_ java兩種經(jīng)典死鎖例子，Lock發(fā)生死鎖案列

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第一種synchronized方式死鎖：

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線(xiàn)程thread1先獲取鎖locka，然后在同步塊里嵌套競爭鎖lockb。而線(xiàn)程thread2先獲取鎖lockb，然后在同步塊里嵌套競爭鎖locka

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（此時(shí)已經(jīng)被線(xiàn)程thread1擁有，而thread1在等待lockb，而lockb被thread2擁有，thread2在等待locka……無(wú)線(xiàn)循環(huán)）。

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package com.app.test;
import org.apache.poi.util.SystemOutLogger;
/**
* Created by lirong5 on 2016/5/24.
*/
public class SyncDeadLock{
private static Object locka = new Object();
private static Object lockb = new Object();
public static void main(String[] args){
new SyncDeadLock().deadLock();
}
private void deadLock(){
Thread thread1 = new Thread(new Runnable() {
@Override
public void run() {
synchronized (locka){
try{
System.out.println(Thread.currentThread().getName()+" get locka ing!");
Thread.sleep(500);
System.out.println(Thread.currentThread().getName()+" after sleep 500ms!");
}catch(Exception e){
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+" need lockb!Just waiting!");
synchronized (lockb){
System.out.println(Thread.currentThread().getName()+" get lockb ing!");
}
}
}
},"thread1");
Thread thread2 = new Thread(new Runnable() {
@Override
public void run() {
synchronized (lockb){
try{
System.out.println(Thread.currentThread().getName()+" get lockb ing!");
Thread.sleep(500);
System.out.println(Thread.currentThread().getName()+" after sleep 500ms!");
}catch(Exception e){
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+" need locka! Just waiting!");
synchronized (locka){
System.out.println(Thread.currentThread().getName()+" get locka ing!");
}
}
}
},"thread2");
thread1.start();
thread2.start();
}
}

執行main方法之后控制臺打印內容如下：

thread1 get locka ing!
thread2 get lockb ing!
thread1 after sleep 500ms!
thread1 need lockb!Just waiting!
thread2 after sleep 500ms!
thread2 need locka! Just waiting!

thread1 need lockb!Just waiting!表明thread1線(xiàn)程進(jìn)入死鎖等待lockb釋放。

thread2 need locka! Just waiting! 表明thread2線(xiàn)程進(jìn)入死鎖等待locka釋放。

第二種concurrent包Lock錯誤使用，導致死鎖：

lock.unlock()；釋放鎖使用地方不規范，導致死鎖不能正常釋放！

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package com.app.test;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* Created by lirong5 on 2016/5/24.
*/
public class LockDeadDemo {
public static void main(String[] args){
final DeadLockBean deadLockBean = new DeadLockBean();
Thread threadA = new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(300);
} catch (InterruptedException e) {
e.printStackTrace();
}
try {
deadLockBean.productDeadLock();
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
},"threadA");
Thread threadB = new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(310);
} catch (InterruptedException e) {
e.printStackTrace();
}
try {
deadLockBean.productDeadLock();
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
},"threadB");
threadA.start();
threadB.start();
try {
System.out.println("main線(xiàn)程即將被join");
threadA.join();
threadB.join();
System.out.println("main線(xiàn)程從join中恢復");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public static class DeadLockBean{
private Lock lock = new ReentrantLock();
public void productDeadLock() throws Throwable {
System.out.println(Thread.currentThread().getName() + " 進(jìn)入了方法！");
lock.lock();
try{
System.out.println(Thread.currentThread().getName() + " 已經(jīng)執行了！");
throw new Throwable("人為拋出異常Throwable");//關(guān)鍵代碼行1，
//throw new Exception("人為拋出異常Exception");//關(guān)鍵代碼行2，不會(huì )死鎖，會(huì )在catch(Exception e中被捕獲)，嵌套lock.unlock()并釋放
}catch(Exception e){
System.out.println(Thread.currentThread().getName()+" 發(fā)生異常catch！");
//lock.unlock();//關(guān)鍵代碼行3，不建議在這里釋放，假如發(fā)生【關(guān)鍵代碼行1】會(huì )產(chǎn)生死鎖
}finally{
System.out.println(Thread.currentThread().getName()+" 發(fā)生異常finally！");
lock.unlock();//關(guān)鍵代碼行4，無(wú)論發(fā)生何種異常，均會(huì )釋放鎖。
}
//lock.unlock();//關(guān)鍵代碼行5，假如發(fā)生不能捕獲異常，將跳出方法體，不執行此處
System.out.println(Thread.currentThread().getName() + " tryCatch外釋放鎖！");
}
}
}

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