Java之同步代码块实现取钱实例

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package 线程同步;public class Account {// 封装账号编号、账号余额的两个成员变量private String accountNo;private double balance;public Account() {}// 构造器public Account(String accountNo, double balance) {this.accountNo = accountNo;this.balance = balance;}public String getAccountNo() {return accountNo;}public void setAccountNo(String accountNo) {this.accountNo = accountNo;}public double getBalance() {return balance;}public void setBalance(double balance) {this.balance = balance;}// 下面两个方法根据accountNo来重写hashCode()和equals()方法public int hashCode() {return accountNo.hashCode();}public boolean equals(Object obj) {if (this == obj)return true;if (obj != null && (obj.getClass() == Account.class)) {Account target = (Account) obj;return target.getAccountNo().equals(accountNo);}return false;}}

package 线程同步;public class DrawThread extends Thread {// 模拟用户账号private Account account;// 当前取钱线程所希望取的钱数private double drawAmount;public DrawThread(String name, Account account, double drawAmount) {super(name);this.account = account;this.drawAmount = drawAmount;}// 当多个线程修改同一个共享数据时，将涉及到数据安全问题public void run() {// 使用account作为同步监视器，任何线程进入下面同步进程块之前// 必须先获得对account账户的锁定---其他线程无法获得说、锁，也无法修改它// 这种做法符合：“加锁->修改->释放锁”的逻辑synchronized (account) {// 账户余额大于或等于取钱数if (account.getBalance() >= drawAmount) {// 吐出钞票System.out.println(getName() + "取钱成功！吐出钞票：" + drawAmount);try {Thread.sleep(1);} catch (InterruptedException e) {e.printStackTrace();}// 修改余额account.setBalance(account.getBalance() - drawAmount);System.out.println("\t余额为：" + account.getBalance());}else{System.out.println(getName()+"取钱失败！余额不足！");}}//同步代码块结束，该线程释放同步锁}}

package 线程同步;public class Test {public static void main(String[] args) {//创建一个账户Account acct = new Account("123456",1000);//模拟两个线程对同一个账户取钱new DrawThread("张三",acct,800).start();;new DrawThread("李四",acct,800).start();;}}

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