package synch;/*** This program shows how multiple threads can safely access a data structure.* * @version 1.31 2015-06-21* @author Cay Horstmann*/
public class SynchBankTest {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 = i;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()));// 在指定的毫秒数内让当前正在执行的线程休眠
                    }} catch (InterruptedException e) {}};Thread t = new Thread(r);// 分配新的 Thread 对象t.start();// 开始线程
        }}
}

package synch;import java.util.*;
import java.util.concurrent.locks.*;/*** A bank with a number of bank accounts that uses locks for serializing access.* * @version 1.30 2004-08-01* @author Cay Horstmann*/
public class Bank {private final double[] accounts;private Lock bankLock;private Condition sufficientFunds;/*** Constructs the bank.* * @param n*            the number of accounts* @param initialBalance*            the initial balance for each account*/public Bank(int n, double initialBalance) {accounts = new double[n];Arrays.fill(accounts, initialBalance);bankLock = new ReentrantLock();sufficientFunds = bankLock.newCondition();}/*** Transfers money from one account to another.* * @param from*            the account to transfer from* @param to*            the account to transfer to* @param amount*            the amount to transfer*/public void transfer(int from, int to, double amount) throws InterruptedException {bankLock.lock();// 加锁try {while (accounts[from] < amount)sufficientFunds.await();// 锁对象的条件对象System.out.print(Thread.currentThread());// 返回对当前正在执行的线程对象的引用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());sufficientFunds.signalAll();// 唤醒所有等待线程} finally {bankLock.unlock();// 解锁
        }}/*** Gets the sum of all account balances.* * @return the total balance*/public double getTotalBalance() {bankLock.lock();// 加锁try {double sum = 0;for (double a : accounts)sum += a;return sum;} finally {bankLock.unlock();// 解锁
        }}/*** Gets the number of accounts in the bank.* * @return the number of accounts*/public int size() {return accounts.length;}
}

package synch2;/*** This program shows how multiple threads can safely access a data structure,* using synchronized methods.* * @version 1.31 2015-06-21* @author Cay Horstmann*/
public class SynchBankTest2 {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 = i;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()));// 在指定的毫秒数内让当前正在执行的线程休眠
                    }} catch (InterruptedException e) {}};Thread t = new Thread(r);// 分配新的 Thread 对象t.start();// 使线程开始执行
        }}
}

package synch2;import java.util.*;/*** A bank with a number of bank accounts that uses synchronization primitives.* * @version 1.30 2004-08-01* @author Cay Horstmann*/
public class Bank {private final double[] accounts;/*** Constructs the bank.* * @param n*            the number of accounts* @param initialBalance*            the initial balance for each account*/public Bank(int n, double initialBalance) {accounts = new double[n];Arrays.fill(accounts, initialBalance);}/*** Transfers money from one account to another.* * @param from*            the account to transfer from* @param to*            the account to transfer to* @param amount*            the amount to transfer*/public synchronized void transfer(int from, int to, double amount) throws InterruptedException {while (accounts[from] < amount)wait();// 添加一个线程到等待集中System.out.print(Thread.currentThread());// 返回对当前正在执行的线程对象的引用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());notifyAll();// 解除等待线程的阻塞状态
    }/*** Gets the sum of all account balances.* * @return the total balance*/public synchronized double getTotalBalance() {double sum = 0;for (double a : accounts)sum += a;return sum;}/*** Gets the number of accounts in the bank.* * @return the number of accounts*/public int size() {return accounts.length;}
}