Java并发学习之十一——同步方法

刺骨的言语ヽ痛彻心扉 2022-08-12 01:25 131阅读 0赞

本文是学习网络上的文章时的总结，感谢大家无私的分享。

每个方法声明为synchronized关键字是一个临界区，Java只允许一个对象执行其中的一个临界区。

静态方法有不同的行为。只有一个执行线程访问被synchronized关键字声明的静态方法，但另一个线程可以访问该类的一个对象中的其他非静态的方法。 你必须非常小心这一点，因为两个线程可以访问两个不同的同步方法，如果其中一个是静态的而另一个不是。如果这两种方法改变相同的数据,你将会有数据不一致 的错误。

package chapter2;
    
    public class Account {
    
    	private double balance;
    
    	public double getBalance() {
    		return balance;
    	}
    
    	public void setBalance(double balance) {
    		this.balance = balance;
    	}
    	
    	public synchronized void addAmount(double amount){
    		double tmp = balance;
    		try {
    			Thread.sleep(10);
    		} catch (InterruptedException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    		tmp+=amount;
    		balance = tmp;
    	}
    	
    	public synchronized void subtractAmount(double amount){
    		double tmp = balance;
    		try {
    			Thread.sleep(10);
    		} catch (InterruptedException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    		tmp-=amount;
    		balance=tmp;
    	}
    	
    	
    }

package chapter2;
    
    public class Bank implements Runnable{
    
    	private Account account;
    	public Bank(Account account) {
    		this.account = account;	
    	}
    	
    	@Override
    	public void run() {
    		// TODO Auto-generated method stub
    		for(int i=0;i<100;i++){
    			account.subtractAmount(1000);
    		}
    	}
    
    }

package chapter2;
    
    public class Company implements Runnable{
    
    	private Account account;
    	public Company(Account account) {
    		this.account = account;	
    	}
    	
    	@Override
    	public void run() {
    		// TODO Auto-generated method stub
    		for(int i=0;i<100;i++){
    			account.addAmount(1000);
    		}
    	}
    
    }

package chapter2;
    
    public class Main {
    
    	/**
    	 * <p>
    	 * </p>
    	 * @author zhangjunshuai
    	 * @date 2014-9-11 下午4:49:50
    	 * @param args
    	 */
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
    		Account account = new Account();
    		account.setBalance(1000);
    		Company company = new Company(account);
    		Thread companyThread = new Thread(company);
    		Bank bank = new Bank(account);
    		Thread bankThread = new Thread(bank);
    		System.out.printf("Account:Initial balance:%f\n", account.getBalance());
    		companyThread.start();
    		bankThread.start();
    		try {
    			companyThread.join();
    			bankThread.join();
    			System.out.printf("Account:Initial balance:%f\n", account.getBalance());
    		} catch (Exception e) {
    			// TODO: handle exception
    			e.printStackTrace();
    		}
    	}
    
    }