久久婷婷香蕉热狠狠综合,精品无码国产自产拍在线观看蜜,寡妇房东在做爰3,中文字幕日本人妻久久久免费,国产成人精品三上悠亚久久

 java允許多線程并發控制，當多個線程同時操作一個可共享的資源變量時(如數據的增刪改查)， 將會導致數據不準確，相互之間產生沖突，因此加入同步鎖以避免在該線程沒有完成操作之前，被其他線程的調用，從而保證了該變量的唯一性和準確性。

我們來看java中第三種同步的方式，使用可重入的鎖。

package com.farsight.thread3;

 import java.util.concurrent.locks.ReentrantLock;

/**

* 封裝賬戶編號，賬戶余額

* @author xj

*

*/

class Account{

// 定義一個可重入的鎖對象

 public final ReentrantLock lock = new ReentrantLock();

private String accountNo;

private double balance;

public Account(){

}

 public Account(String accountNo, double balance){

this.accountNo = accountNo;

this.balance = balance;

}

public String getAccountNo() {

return accountNo;

}

public void setAccountNo(String accountNo) {

this.accountNo = accountNo;

}

public double getBalance() {

return balance;

}

public void draw(double drawAmount){

// 加鎖

lock.lock();

try{

// 賬戶余額大于取錢的數目

if(balance >= drawAmount){

 System.out.println(Thread.currentThread().getName() + "取錢成功! 吐出鈔票: " + drawAmount);

//人為制造cpu調度，使并發產生

try {

Thread.sleep(1);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

// 修改余額

balance -= drawAmount;

}

else{

 System.out.println(Thread.currentThread().getName() + "取錢失敗!余額不足!");

}

}

finally {

// 釋放鎖

lock.unlock();

}

}

@Override

public int hashCode() {

final int prime = 31;

int result = 1;

result = prime * result

 + ((accountNo == null) ? 0 : accountNo.hashCode());

long temp;

temp = Double.doubleToLongBits(balance);

 result = prime * result + (int) (temp ^ (temp >>> 32));

return result;

}

@Override

public boolean equals(Object obj) {

if (this == obj)

return true;

if (obj == null)

return false;

if (getClass() != obj.getClass())

return false;

Account other = (Account) obj;

if (accountNo == null) {

if (other.accountNo != null)

return false;

}

else if (!accountNo.equals(other.accountNo))

return false;

 if (Double.doubleToLongBits(balance) != Double

.doubleToLongBits(other.balance))

return false;

return true;

}

}

/**

* 定義一個取錢的線程類，該線程類根據執行賬戶、取錢

* 數量進行取錢操作，余額不足時無法提取現金。

* @author xj

*

*/

class DrawThread extends Thread{

// 定義一個用戶類，取錢數量

private Account account;

private double drawAmount;

 public DrawThread(String name, Account account, double drawAmount){

super(name);

this.account = account;

this.drawAmount = drawAmount;

}

public void run(){

account.draw(drawAmount);

}

}

public class ThreadDemon3 {

public static void main(String[] args) {

// 創建一個模擬戶

 Account acct = new Account("1234567", 10000);

//模擬兩個線程對同一個賬戶取錢

 new DrawThread("甲", acct, 6000).start();

 new DrawThread("乙", acct, 5000).start();

}

}