《面向对象程序设计（java）》第十七周学习总结
第一部分：实验部分
实验名称：实验十七 线程同步控制
1、实验目的与要求
(1) 掌握线程同步的概念及实现技术；
(2) 线程综合编程练习
2、实验内容和步骤
实验1：测试程序并进行代码注释。
测试程序1：
l 在Elipse环境下调试教材651页程序14-7，结合程序运行结果理解程序；
l 掌握利用锁对象和条件对象实现的多线程同步技术。
1 package synch;
2
3 import java.util.*;
4 import java.util.concurrent.locks.*;
5
6 /**
7 * A bank with a number of bank accounts that uses locks for serializing access.
8 * @version 1.30 2004-08-01
9 * @author Cay Horstmann
10 */
11 public class Bank
12 {
13 private final double[] accounts;//银行运转的基本数据
14 private Lock bankLock;//锁对象
15 private Condition sufficientFunds;//
16
17 /**
18 * Constructs the bank.
19 * @param n the number of accounts
20 * @param initialBalance the initial balance for each account
21 */
22 public Bank(int n, double initialBalance)
23 {
24 accounts = new double[n];
25 Arrays.fill(accounts, initialBalance);
26 bankLock = new ReentrantLock();
27 sufficientFunds = bankLock.newCondition();
28 }
29
30 /**
31 * Transfers money from one account to another.
32 * @param from the account to transfer from
33 * @param to the account to transfer to
34 * @param amount the amount to transfer
35 */
36 public void transfer(int from, int to, double amount) throws InterruptedException
37 {
38 bankLock.lock();
39 try
40 {//锁对象的引用条件对象
41 while (accounts[from] < amount)
42 sufficientFunds.await();
43 System.out.print(Thread.currentThread());//打印出线程号
44 accounts[from] -= amount;
45 System.out.printf(" %10.2f from %d to %d", amount, from, to);
46 accounts[to] += amount;
47 System.out.printf(" Total Balance: %10.2f%n", getTotalBalance());
48 sufficientFunds.signal();
49 }
50 finally
51 {
52 bankLock.unlock();
53 }
54 }
55
56 /**
57 * Gets the sum of all account balances.
58 * @return the total balance
59 */
60 public double getTotalBalance()
61 {
62 bankLock.lock();//加锁
63 try
64 {
65 double sum = 0;
66
67 for (double a : accounts)
68 sum += a;
69
70 return sum;
71 }
72 finally
73 {
74 bankLock.unlock();//解锁
75 }
76 }
77
78 /**
79 * Gets the number of accounts in the bank.
80 * @return the number of accounts
81 */
82 public int size()
83 {
84 return accounts.length;
85 }
86 }
1 package synch;
2
3 /**
4 * This program shows how multiple threads can safely access a data structure.
5 * @version 1.31 2015-06-21
6 * @author Cay Horstmann
7 */
8 public class SynchBankTest
9 {
10 public static final int NACCOUNTS = 100;
11 public static final double INITIAL_BALANCE = 1000;
12 public static final double MAX_AMOUNT = 1000;
13 public static final int DELAY = 10;
14
15 public static void main(String[] args)
16 {
17 Bank bank = new Bank(NACCOUNTS, INITIAL_BALANCE);
18 for (int i = 0; i < NACCOUNTS; i++)
19 {
20 int fromAccount = i;
21 Runnable r = () -> {
22 try
23 {
24 while (true)
25 {
26 int toAccount = (int) (bank.size() * Math.random());
27 double amount = MAX_AMOUNT * Math.random();
28 bank.transfer(fromAccount, toAccount, amount);
29 Thread.sleep((int) (DELAY * Math.random()));
30 }
31 }
32 catch (InterruptedException e)
33 {
34 }
35 };
36 Thread t = new Thread(r);
37 t.start();
38 }
39 }
40 }运行结果如下：
测试程序2：
l 在Elipse环境下调试教材655页程序14-8，结合程序运行结果理解程序；
l 掌握synchronized在多线程同步中的应用。
1 package synch2;
2
3 import java.util.*;
4
5 /**
6 * A bank with a number of bank accounts that uses synchronization primitives.
7 * @version 1.30 2004-08-01
8 * @author Cay Horstmann
9 */
10 public class Bank
11 {
12 private final double[] accounts;
13
14 /**
15 * Constructs the bank.
16 * @param n the number of accounts
17 * @param initialBalance the initial balance for each account
18 */
19 public Bank(int n, double initialBalance)
20 {
21 accounts = new double[n];
22 Arrays.fill(accounts, initialBalance);
23 }
24
25 /**
26 * Transfers money from one account to another.
27 * @param from the account to transfer from
28 * @param to the account to transfer to
29 * @param amount the amount to transfer
30 */
31 public synchronized void transfer(int from, int to, double amount) throws InterruptedException
32 {
33 while (accounts[from] < amount)
34 wait();//导致线程进入等待状态直到它被通知。该方法只能在一个同步方法中调用。
35 System.out.print(Thread.currentThread());//打印出线程号
36 accounts[from] -= amount;
37 System.out.printf(" %10.2f from %d to %d", amount, from, to);//第一个打印结果保留两位小数（最大范围是十位），
38 accounts[to] += amount;
39 System.out.printf(" Total Balance: %10.2f%n", getTotalBalance());
40 notifyAll();//解除那些在该对象上调用wait方法的线程阻塞状态。该方法只能在同步方法或同步块内部调用。
41 }
42
43 /**
44 * Gets the sum of all account balances.
45 * @return the total balance
46 */
47 public synchronized double getTotalBalance()
48 {
49 double sum = 0;
50
51 for (double a : accounts)
52 sum += a;
53
54 return sum;
55 }
56
57 /**
58 * Gets the number of accounts in the bank.
59 * @return the number of accounts
60 */
61 public int size()
62 {
63 return accounts.length;
64 }
65 }
1 package synch2;
2
3 /**
4 * This program shows how multiple threads can safely access a data structure,
5 * using synchronized methods.
6 * @version 1.31 2015-06-21
7 * @author Cay Horstmann
8 */
9 public class SynchBankTest2
10 {
11 public static final int NACCOUNTS = 100;
12 public static final double INITIAL_BALANCE = 1000;
13 public static final double MAX_AMOUNT = 1000;
14 public static final int DELAY = 10;
15
16 public static void main(String[] args)
17 {
18 Bank bank = new Bank(NACCOUNTS, INITIAL_BALANCE);
19 for (int i = 0; i < NACCOUNTS; i++)
20 {
21 int fromAccount = i;
22 Runnable r = () -> {
23 try
24 {
25 while (true)
26 {
27 int toAccount = (int) (bank.size() * Math.random());
28 double amount = MAX_AMOUNT * Math.random();
29 bank.transfer(fromAccount, toAccount, amount);
30 Thread.sleep((int) (DELAY * Math.random()));
31 }
32 }
33 catch (InterruptedException e)
34 {
35 }
36 };
37 Thread t = new Thread(r);
38 t.start();
39 }
40 }
41 }运行结果如下：
y
测试程序3：
l 在Elipse环境下运行以下程序，结合程序运行结果分析程序存在问题；
l 尝试解决程序中存在问题。
| class Cbank { private static int s=2000; public static void sub(int m) { int temp=s; temp=temp-m; try { Thread.sleep((int)(1000*Math.random())); } catch (InterruptedException e) { } s=temp; System.out.println("s="+s); } }
class Customer extends Thread { public void run() { for( int i=1; i<=4; i++) Cbank.sub(100); } } public class Thread3 { public static void main(String args[]) { Customer customer1 = new Customer(); Customer customer2 = new Customer(); customer1.start(); customer2.start(); } } |
1 class Cbank
2 {
3 private static int s=2000;
4 synchronized public static void sub(int m)
5 {
6 int temp=s;
7 temp=temp-m;
8 try {
9 Thread.sleep((int)(1000*Math.random()));
10 }
11 catch (InterruptedException e) { }
12 s=temp;
13 System.out.println("s="+s);
14 }
15 }
16
17
18 class Customer extends Thread
19 {
20
21 public void run()
22 {
23 for( int i=1; i<=4; i++)
24 Cbank.sub(100);
25 }
26 }
27 public class Thread3
28 {
29 public static void main(String args[])
30 {
31 Customer customer1 = new Customer();
32 Customer customer2 = new Customer();
33 customer1.start();
34 customer2.start();
35 }
36 }运行结果如下：
实验2 编程练习
利用多线程及同步方法，编写一个程序模拟火车票售票系统，共3个窗口，卖10张票，程序输出结果类似（程序输出不唯一，可以是其他类似结果）。
Thread-0窗口售：第1张票
Thread-0窗口售：第2张票
Thread-1窗口售：第3张票
Thread-2窗口售：第4张票
Thread-2窗口售：第5张票
Thread-1窗口售：第6张票
Thread-0窗口售：第7张票
Thread-2窗口售：第8张票
Thread-1窗口售：第9张票
Thread-0窗口售：第10张票
1 public class Demo {
2 public static void main(String[] args) {
3 Mythread mythread = new Mythread();
4 Thread t1 = new Thread(mythread);
5 Thread t2 = new Thread(mythread);
6 Thread t3 = new Thread(mythread);
7 t1.start();
8 t2.start();
9 t3.start();
10 }
11 }
12
13 class Mythread implements Runnable {
14 int t = 1;
15 boolean flag = true;
16
17 @Override
18 public void run() {
19 // TODO Auto-generated method stub
20 while (flag) {
21 try {
22 Thread.sleep(500);
23 } catch (Exception e) {
24 // TODO: handle exception
25 e.printStackTrace();
26 }
27
28 synchronized (this) {
29 if (t <= 10) {
30 System.out.println(Thread.currentThread().getName() + "窗口售：第" + t + "张票");
31 t++;
32 }
33 if (t > 10) {
34 flag = false;
35 }
36 }
37
38 }
39 }
40 }
运行结果如下：
4. 实验总结：
通过本学期的实验课程学习，真的学到了很多，尤其是在老师和助教学长的耐心指导下，从最开始JDK的安装到后来自己能写出可以运行的程序，很开心。
来源：oschina
链接：https://my.oschina.net/u/4415618/blog/4154130