测试用储户实体类:
package domain;
import java.util.ArrayList;
/**
* 规避死锁问题的共享存取实体类
*
* @author WanAkiko
*
*/
public class Depositor {
private String account;
private Double balance;
private ArrayList<Depositor> list = new ArrayList<Depositor>();
public Depositor() {
super();
}
public Depositor(String account, Double balance) {
super();
this.account = account;
this.balance = balance;
}
/**
* 资金收入
*/
public void earning(Double money) {
this.balance += money;
}
/**
* 资金支出
*/
public void expenditure(Double money) {
this.balance -= money;
}
/**
* 资源上锁
*
* @param depThis
* @param depThat
* @return
*/
public synchronized boolean resourceLocked(Depositor depThis,
Depositor depThat) {
// 若对象序列中存在任意携锁对象则无需继续上锁
if (list.contains(depThis) || list.contains(depThat) || list.size() > 0) {
return false;
}
list.add(depThis);
list.add(depThat);
return true;
}
/**
* 资源释放
*
* @param depThis
* @param depThat
*/
public synchronized void resourceRelease(Depositor depThis,
Depositor depThat) {
list.remove(depThis);
list.remove(depThat);
}
public String getAccount() {
return account;
}
public void setAccount(String account) {
this.account = account;
}
public Double getBalance() {
return balance;
}
public void setBalance(Double balance) {
this.balance = balance;
}
@Override
public String toString() {
return "Depositor [account=" + account + ", balance=" + balance + "]";
}
}
转账线程:
package domain;
import java.util.concurrent.locks.ReentrantLock;
/**
* 转账线程(打破单独持有,互相等待的僵局)
*
* @author WanAkiko
*
*/
public class WaitEachOtherThread implements Runnable {
private Depositor incomeObject; // 收入对象
private Depositor spendingObject; // 支出对象
private Double money = 0.0; // 交易金额
private ReentrantLock iLock; // 收入锁
private ReentrantLock sLock; // 支出锁
/**
* 转账线程全参构造
*
* @param 收入账户
* @param 支出账户
* @param 单位金额
* @param 收入锁
* @param 支出锁
*/
public WaitEachOtherThread(Depositor incomeObject,
Depositor spendingObject, Double money, ReentrantLock iLock,
ReentrantLock sLock) {
super();
this.incomeObject = incomeObject;
this.spendingObject = spendingObject;
this.money = money;
this.iLock = iLock;
this.sLock = sLock;
}
@Override
public void run() {
while (true) {
// 仅当锁对象未被其它线程使用时才获取该锁
if (iLock.tryLock() && sLock.tryLock()) {
try {
// 收入对象的余额大于或等于目标金额时
if (spendingObject.getBalance() >= money) {
spendingObject.expenditure(money); // 资金支出
incomeObject.earning(money); // 资金收入
System.out.println("出账用户-"
+ spendingObject.getAccount() + ",剩余余额:"
+ spendingObject.getBalance() + "¥;进账用户-"
+ incomeObject.getAccount() + ",当前余额:"
+ incomeObject.getBalance() + "¥");
}
} finally {
// 循环释放线程锁,预防“超出最大锁数量”的错误(Maximum lock count exceeded)
iLock.unlock();
sLock.unlock();
}
}
}
}
}
死锁规避测试:
package test;
import java.util.concurrent.locks.ReentrantLock;
import domain.Depositor;
import domain.WaitEachOtherThread;
/**
* 规避线程死锁(打破单独持有,互相等待的僵局)
*
* @author WanAkiko
*
*/
public class BreakWaitTest {
public static void main(String[] args) {
Depositor incomeObject = new Depositor("WanAkiko", 1000.0);
Depositor spendingObject = new Depositor("WanQuee", 2000.0);
ReentrantLock iLock = new ReentrantLock();
ReentrantLock sLock = new ReentrantLock();
new Thread(new WaitEachOtherThread(incomeObject, spendingObject, 2.0, iLock, sLock)).start();
new Thread(new WaitEachOtherThread(incomeObject, spendingObject, 5.0, iLock, sLock)).start();
}
}
运行示例: