同一把锁

public class SynchronizedClass extends Thread{
    private Account account;
    private double drawbalance;
    Object obj;
    public SynchronizedClass(String name,Account account,double drawbalance,Object obj){
        super(name);
        this.account=account;
        this.drawbalance=drawbalance;
        this.obj=obj;
        //start();
    }
    public void run(){
        try{sleep(100);}catch(Exception e){}
        synchronized(obj){
            if(drawbalance>account.getBalance()){
                System.out.println("余额不足！");
            }else{
                System.out.println("吐钱成功！");
                try{
                    sleep(100);
                    System.out.println("取钱："+drawbalance);
                    account.setBalance(account.getBalance()-drawbalance);
                    System.out.println("余额为："+account.getBalance());
                }catch(Exception e){
                    System.out.println(e);
                }
            }
        }
        
        
    }
    public static void main(String[] args){
    
        Object o=new Object();//传到了两个线程中，保证了是同一个锁。
        Account a=new Account("刘腾",100000);
        new SynchronizedClass("A线程",a,100000,o).start();
        new SynchronizedClass("B线程",a,10000,o).start();
    }    
}

//账户
class Account {
    private String name;
    private double balance;
    public Account(){}
    public Account(String name,double balance){
        this.name=name;
        this.balance=balance;
    }
    public void setName(String name){
        this.name=name;
    }
    public void setBalance(double balance){
        this.balance=balance;
    }
    public String getName(){
        return name;
    }
    public double getBalance(){
        return balance;
    }
    
    /*
    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(other.name==name&&other.balance==balance)return true;
        else return false;
    }
    */
}