Java核心技术学习---多线程，锁，同步，条件对象部分应用源码

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Bank.java

package testcase;import java.util.*;import java.util.concurrent.locks.*;//考虑同步的多线程编程public class Bank {private final double[] accounts;private Lock bankLock;private Condition sufficientFunds;public Bank(int n,double initialBalance){accounts = new double[n];Arrays.fill(accounts,initialBalance);bankLock = new ReentrantLock(); //构建一个可被用来保护临界区的可重入锁sufficientFunds = bankLock.newCondition(); //获得条件对象，一个锁可以有多个条件对象}public void transfer(int from,int to,double amount) throws InterruptedException{   //用ReentrantLock保护代码块bankLock.lock(); //一个ReentrantLock对象 锁对象try {//若满足以下条件（余额不足），则阻塞当前线程，放弃锁，//这样使其他线程可以进行增加余额的操作。while(accounts[from] < amount) { sufficientFunds.await(); //当前线程被阻塞}System.out.println(Thread.currentThread());accounts[from] -=amount;System.out.printf("%10.2f from %d to %d",amount,from,to);accounts[to] += amount;System.out.printf("Total Balance:10.2f%n",getTotalBalance());//当另一个线程调用同一条件的signalAll方法时，锁可用且处于阻塞状态的线程才能解除阻塞。sufficientFunds.signalAll();//该调用重新激活因为该条件而等待的所有线程//signalAll();不会立即激活一个等待线程，仅仅解除等待线程的阻塞，以便这些线程可以在//当前线程退出同步方法后，通过竞争实现对对象的访问。}finally {//解锁操作放在finally子句之内至关重要。若临界区代码抛出异常，锁必须被释放，//否在其他线程将永远阻塞bankLock.unlock(); //解锁操作}}public double getTotalBalance(){bankLock.lock();try{double sum = 0;for(double a :accounts) {sum += a;}return sum;}finally{bankLock.unlock();}}public int size(){return accounts.length;}}

SynBankTest.java

package testcase;public class SynBankTest {public static final int NACCOUNTS = 100;public static final double INITIAL_BALANCE = 1000;public static final double MAX_AMOUNT = 1000;public static final int DELAY = 10;public static void main(String[] args){Bank bank = new Bank(NACCOUNTS,INITIAL_BALANCE);for(int i = 0;i < NACCOUNTS; i++){int fromAccount = 0;Runnable r = ()->{try{while(true){int toAccount = (int)(bank.size()*Math.random());double amount = MAX_AMOUNT * Math.random();bank.transfer(fromAccount, toAccount, amount);Thread.sleep((int)(DELAY*Math.random()));}}catch(InterruptedException e) {}};Thread t = new Thread(r);t.start(); //开启线程}}}

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