Java多线程2

最新推荐文章于 2024-11-28 15:37:50 发布

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最新推荐文章于 2024-11-28 15:37:50 发布

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分类专栏： Java基础文章标签： java 线程竞争多线程

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Java多线程中访问同一资源时容易引发资源竞争，而线程互斥是解决线程间资源竞争的手段。

线程互斥：若干个线程若要使用同一共享资源，任何时刻最多允许一个线程使用，其他要使用该资源的线程必须要等待，直到占有资源的线程释放资源。

Java利用synchronized实现资源互斥

synchronized有两种用法：

1.同步方法：

语法格式如下:

public synchronized void func(){
    //Code
}

2.同步块

语法格式如下：

synchronized(syncObject){
    //Code
}

一个多线程解决资源竞争的典型案例：

class Account{

    private String name;
    private double balance;
    public Account() {
        super();
        // TODO Auto-generated constructor stub
    }
    public Account(String name, double balance) {
        super();
        this.name = name;
        this.balance = 0;
    }



    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public double getBalance() {
        return balance;
    }
    public void setBalance(double balance) {
        this.balance = balance;
    }
    public void put(double value){
        if(value>0){
            this.balance+=value;
        }
    }

    public double get(double value){

        if(value<0){
            return 0;
        }
        else if(value<=this.balance){
            this.balance-=value;
        }
        else{
            value = this.balance;
            this.balance=0;
        }
        return value;
    }

}

class LockFetchThread extends Thread{

    private Account account;
    private double value;
    public LockFetchThread(Account account, double value) {
        super();
        this.account = account;
        this.value = value;
    }


    @Override
    public void run(){
        synchronized(this.account){
            double howmatch = this.account.getBalance();
            try {
                Thread.sleep(1000);
            } catch (Exception e) {
                // TODO: handle exception
            }

            System.out.println(this.account.getName()+"账户：现有"+howmatch+",取走"+this.account.get(this.value)+",余额"+this.account.getBalance());

        }
    }

}
public class LockSaveThread extends Thread{

    private Account account;
    private double value;

    public LockSaveThread(Account account, double value) {
        super();
        this.account = account;
        this.value = value;
    }

    @Override
    public void run(){
        synchronized(this.account){
            double howmatch = this.account.getBalance();
            try {
                Thread.sleep(1000);
            } catch (Exception e) {
                // TODO: handle exception
            }
            this.account.put(this.value);
            System.out.println(this.account.getName()+"账户：现有"+howmatch+",存入"+this.value+",余额"+this.account.getBalance());

        }
    }

    public static void main(String[] args){
        Account wang = new Account("wang",0);
        (new LockSaveThread(wang, 100)).start();
        (new LockSaveThread(wang, 200)).start();
        (new LockSaveThread(wang, 300)).start();
        (new LockFetchThread(wang, 300)).start();

    }
}