Java多线程并发疑问：锁机制实例分析

原创﹏ヽ暗。殇╰゛Y 2024-09-19 02:21 72阅读 0赞

在Java中，锁机制是多线程安全访问共享资源的关键。这里我们将通过一个简单的银行账户转账的例子来详细分析锁机制。

假设我们有以下两个类：

1. `Account`：
```java
public class Account {
    private int balance;
    // getters and setters

public synchronized void transfer(Account from, Account to, int amount)) {
        // Transfer logic here
        if (amount > from.getBalance()) {
            throw new IllegalArgumentException("Insufficient funds.");
        }
        from.decreaseBalance(amount);
        to.increaseBalance(amount);
        System.out.println("Transfer completed successfully.");
    }
}
```

2. `Bank`：
```java
public class Bank {
    private Map<Account, Account> transfers;

public synchronized Bank() {
        this.transfers = new HashMap<>();
    }

public synchronized void registerAccount(Account account) {
        transfers.put(account, null);
        System.out.println("Account registered successfully.");
    }

public synchronized void transfer(Account from, Account to, int amount)) {
        if (transfers.containsKey(from)) {
            Account assignedTo = transfers.get(from);
            transfers.remove(from);
            if (assignedTo != null) {
                transfers.put(assignedTo, to);
            } else {
                // No assignment, so just add the transfer
                transfers.put(from, to);
            }
        } else {
            System.out.println("Account not registered. Transfer cannot be completed.");
            return;
        }

from.transfer(to, amount);
        System.out.println("Transfer initiated successfully.");
    }

public synchronized void cancelTransfer(Account from) {
        if (transfers.containsKey(from)) {
            Account assignedTo = transfers.get(from);
            if (assignedTo != null) {
                transfers.put(assignedTo, null);
            } else {
                // No assignment, so just remove the transfer
                transfers.remove(from);
            }
        }

System.out.println("Transfer cancellation initiated successfully.");
    }
}
```

在这个例子中，`Account`类用于存储账户的余额，而`Bank`类则用于管理多个账户之间的转账操作。

我们通过`Bank`对象来注册账户、进行转账和取消转账。在每次转账操作前，我们都使用了`synchronized`关键字来确保同一时刻只有一个线程可以执行转账逻辑，从而保证了数据的完整性和一致性。