[Java知识库]Java多线程与并发编程：使用 lock 类和多线程管理newCondition/wait/signal/signalAll 实现账户存提款

(使用 lock 类和多线程管理newCondition/wait/signal/signalAll 实现) 假设创建并启动两个任务，一个用来向账户中存款，存入一个随机金额 (Math.random()100)，另外一个从同一账户中提款，提款一个随机金额(Math.random()100)。当提款的数额大于账户的当前余额时，提款线程必须等待。不管什么时候，只要向账户新存入一笔资金，存储线程必须通知提款线程重新尝试。如果余额仍未达到提款的数额，提款线程必须继续等待新的存款。

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Demo {

    private static Account account = new Account();
    
    public static void main(String[] args) {
        ExecutorService executor = Executors.newFixedThreadPool(2);
        executor.execute(new DepositTask());
        executor.execute(new WithdrawTask());
        executor.shutdown();
        System.out.println("Thread 1\t\tThread 2\t\tBalance");
    }
    
    public static class DepositTask implements Runnable {
        public void run() {
            try {
                while (true) {
                    account.deposit((int) (Math.random() * 10) + 1);
                    Thread.sleep(1000);
                }
            }
            catch (InterruptedException ex) {
                ex.printStackTrace();
            }
        }
    }
    
    public static class WithdrawTask implements Runnable {
        public void run() {
            while (true) {
                account.withDraw((int) (Math.random() * 10) + 1);
            }
        }
    }
    
    public static class Account {
        
        private static Lock lock = new ReentrantLock();
        
        private static Condition newDeposit = lock.newCondition();
        
        private int balance = 0;
        
        public int getBalance() {
            return balance;
        }
        
        public void withDraw(int amount) {
            lock.lock();
            try {
                while (balance < amount) {
                    newDeposit.await();
                }
                balance -= amount;
                System.out.println("\t\t\tWithdraw " + amount + "\t\t" + getBalance());
            }
            catch (InterruptedException ex) {
                ex.printStackTrace();
            }
            finally {
                lock.unlock();
            }
        }
        
        public void deposit(int amount) {
            lock.lock();
            try {
                balance += amount;
                System.out.println("Deposit " + amount + "\t\t\t\t\t" + getBalance());
                newDeposit.signalAll();
            }
            finally {
                lock.unlock();
            }
        }
        
    }
    
}*/
 import java.util.concurrent.*;
 import java.util.concurrent.locks.*;
 public class Main1 {
     private static Account account = new Account();
      public static void main(String[] args) {         
    	  ExecutorService executor = Executors.newFixedThreadPool(2);
         System.out.println("Thread 1\t\tThread 2\t\t\t\tBalance");
         executor.execute(new DepositTask());       
         executor.execute(new WithdrawTask());
         executor.shutdown();
     }
     public static class DepositTask implements Runnable {         
    	 @Override
         public void run() {
             try{
                 while(true) {
                     account.deposit((int)(Math.random() * 10) + 1);
                     Thread.sleep(1000);
                }
             } catch(Exception ex) {
                 ex.printStackTrace();
             }
         }
     }
     public static class WithdrawTask implements Runnable {
         @Override
         public void run() {
             while(true) {
	account.withdraw((int)(Math.random() * 10) + 1);
             }
         }
     }
     private static class Account {
         private static Lock lock = new ReentrantLock();
         private static Condition newDeposit = lock.newCondition();
         private int balance = 0;
         public int getBalance() {
             return balance;
         }
         public void withdraw(int amount) {
             lock.lock();
             try{
                 while(balance < amount) {
                     System.out.println("\t\t\tWait for a deposit.");
                     newDeposit.await();
                 }
                 balance -= amount;
                 System.out.println("\t\t\tWithdraw " + 
                         amount + "\t\t\t\t" + getBalance());
                 
             } catch (InterruptedException ex) {
                 ex.printStackTrace();
             } finally {
                 lock.unlock();
             }
         }
         public void deposit(int amount) {
             lock.lock();
             try{
                 balance += amount;
                 System.out.println("Deposit " + 
                        amount + "\t\t\t\t\t\t\t\t" + getBalance());              
                 newDeposit.signal();
             } catch (IllegalMonitorStateException e) {
                 e.printStackTrace();
             } finally {                
            	 lock.unlock();
            }
         }
     }
 }