Java线程同步实战：解决多线程共享资源冲突

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
/**
 * 线程同步测试主类
 */
public class TestMain5 extends JFrame {
 private MyAccounts myAccounts = null; // 共享账号资源
 private JTextField text = null; // 显示当前余额
 private JTextArea textArea = null; // 显示交易流水日志
 private JButton button = null; // 触发动作按钮
 
 /**
  * 构造一个银行存取款模拟界面
  */
 public TestMain5(){
  super("线程同步测试");
  myAccounts = new MyAccounts();
  // 初始余额设为1100
  text = new JTextField(Integer.toString(myAccounts.inquire()), 10); 
  textArea = new JTextArea();
  textArea.setText("交易日志：\n");
  JScrollPane sp = new JScrollPane(textArea);
  
  button = new JButton("开始交易");
  button.addActionListener(new ActionListener(){
   public void actionPerformed(ActionEvent e) {
    // 模拟6家支行同时进行业务
    new Bank("钟楼支行", myAccounts, Bank.DEAL_SAVING, 800);
    new Bank("高新支行", myAccounts, Bank.DEAL_SAVING, 1300);
    new Bank("小寨支行", myAccounts, Bank.DEAL_FETCH, 200);
    new Bank("雁塔支行", myAccounts, Bank.DEAL_FETCH, 400);
    new Bank("兴庆支行", myAccounts, Bank.DEAL_SAVING, 100);
    new Bank("土门支行", myAccounts, Bank.DEAL_FETCH, 700);
   }
  });
  
  JPanel pane = new JPanel();
  pane.add(text);
  pane.add(button);
  this.getContentPane().add(pane, BorderLayout.NORTH);
  this.getContentPane().add(sp);
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  this.setSize(300, 200);
  this.setLocationRelativeTo(null);
  this.setVisible(true);
 }
 
 /**
  * 银行交易大厅线程类
  */
 class Bank extends Thread{
  public static final int DEAL_SAVING = 0; // 存款
  public static final int DEAL_FETCH = 1;  // 取款
  
  private int actionType; // 动作类型
  private int amount;     // 金额
  private MyAccounts account; // 共享账号
  
  /**
   * 构造并立即启动线程
   */
  public Bank(String name, MyAccounts account, int actionType, int amount){
   super(name);
   this.account = account;
   this.actionType = actionType;
   this.amount = amount;
   this.start();
  }
  
  public void run(){
   int resultBalance = 0;
   String actionName = "";
   
   if(actionType == Bank.DEAL_SAVING){ 
    resultBalance = account.saving(amount);
    actionName = "存款";
   }else { 
    resultBalance = account.fetch(amount);
    actionName = "取款";
   }
   
   // 更新UI显示
   text.setText(Integer.toString(resultBalance));
   textArea.append(this.getName() + " " + actionName + " " + amount + " 结余：" + resultBalance + "\n");
  }
 }
 
 /**
  * 账号管理核心类（涉及同步）
  */
 class MyAccounts{
  private Integer balance = 1100; // 初始余额
  
  /**
   * 查询余额
   */
  public synchronized int inquire(){
   return balance;
  }
  
  /**
   * 存款业务
   */
  public synchronized int saving(int c){
   // 为保证可见性演示，逐步操作：先查、改、再写回
   int currentBalance = inquire(); 
   currentBalance += c;
   try {
    Thread.sleep(1000); // 模拟网络延迟或处理耗时
   } catch (InterruptedException ex) {
    ex.printStackTrace();
   }
   balance = currentBalance; 
   return inquire(); 
  }
  
  /**
   * 取款业务
   */
  public synchronized int fetch(int c){
   int currentBalance = inquire(); 
   currentBalance -= c;
   try {
    Thread.sleep(1000);
   } catch (InterruptedException ex) {
    ex.printStackTrace();
   }
   balance = currentBalance; 
   return inquire(); 
  }
 }
 
 public static void main(String [] args){
  new TestMain5();
 }
}