(主推) 死锁总结 - 黑马程序员技术交流社区

public class DeadLockDemo {
public static void main(String[] args) {
DeadLock d = new DeadLock();
Thread a = new Thread(d);
Thread b = new Thread(d);
a.start();
b.start();
}
}
class DeadLock implements Runnable{
private boolean flag = true;//控制线程的操作交替进行
private final Object l = new Object();
private final Object m = new Object();//定义两个静态锁
public void run(){
while(true){
if(flag){
synchronized(l){//①
System.out.println("...if l...");
synchronized(m){//②
System.out.println("...if m...");
}
}
flag = false;
}else{
synchronized(m){//③
System.out.println("...else m...");
synchronized(l){//④
System.out.println("...else l...");
}
}
flag = true;
}
}
}
}

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/*
* 需求：简单的银行转账,它将资金从一个账户转到另一个账户
* 在开始转账之前，需要获得两个Account的锁，以确保以原子的方式更新账户中的余额，且不能破坏不可变的条件，如账户的余额不能为负数
*/
/*账户类*/
class Account{
private String accountName;//账号
private int balance;//资金总额
public Account(String accountName,int balance){
this.accountName = accountName;
this.balance = balance;
}
/**/
public String getAccountName() {//获取账号
return accountName;
}
public int getBalance() {//获取账号余额
return balance;
}
public void debit(int amount){//更新转出方余额
this.balance -= amount;
}
public void credbit(int amount){//更新转入方余额
this.balance += amount;
}
}
class TransferAccount implements Runnable{
public Account fromAccount;//转出账户
public Account toAccount;//转入账户
public int amount;//转出金额
public TransferAccount(Account fromAccount,Account toAccount,int amount){
this.fromAccount = fromAccount;
this.toAccount = toAccount;
this.amount = amount;
}
public void run(){
while(true){
synchronized(fromAccount){
synchronized(toAccount){
if(fromAccount.getBalance() <= 0){//转账进行的条件：判断转出账户的余额是否大于0
System.out.println(fromAccount.getAccountName() + "账户余额不足，无法进行转账");
return;
}else{
fromAccount.debit(amount);//更新转出账户的余额：-
toAccount.credbit(amount);//更新转入账户的余额：+
}
}
}
System.out.println(fromAccount.getAccountName() + "......" + fromAccount.getBalance());//打印转出账户的余额
System.out.println(toAccount.getAccountName() + "---" + toAccount.getBalance());//打印转入账户的余额
}
}
}
public class BankTransfer {
public static void main(String[] args) {
Account fromAccount = new Account("张三",100000);
Account toAccount = new Account("李四",200000);
Thread a = new Thread(new TransferAccount(fromAccount,toAccount,1));
Thread b = new Thread(new TransferAccount(toAccount,fromAccount,2));
a.start();
b.start();
}
}

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