1、實驗目的與要求

(1)?掌握線程同步的概念及實現技術；?

(2)?線程綜合編程練習

2、實驗內容和步驟

實驗1：測試程序并進行代碼注釋。

測試程序1：

l?在Elipse環境下調試教材651頁程序14-7，結合程序運行結果理解程序；

l?掌握利用鎖對象和條件對象實現的多線程同步技術。

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()));// 在指定的毫秒數內讓當前正在執行的線程休眠 }} catch (InterruptedException e) {}};Thread t = new Thread(r);// 分配新的 Thread 對象t.start();// 開始線程 }} }SynchBankTest 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();// 加鎖try {while (accounts[from] < amount)sufficientFunds.await();// 鎖對象的條件對象System.out.print(Thread.currentThread());// 返回對當前正在執行的線程對象的引用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();// 喚醒所有等待線程} finally {bankLock.unlock();// 解鎖 }}/*** Gets the sum of all account balances.* * @return the total balance*/public double getTotalBalance() {bankLock.lock();// 加鎖try {double sum = 0;for (double a : accounts)sum += a;return sum;} finally {bankLock.unlock();// 解鎖 }}/*** Gets the number of accounts in the bank.* * @return the number of accounts*/public int size() {return accounts.length;} }Bank

測試程序2：

l?在Elipse環境下調試教材655頁程序14-8，結合程序運行結果理解程序；

l?掌握synchronized在多線程同步中的應用。

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()));// 在指定的毫秒數內讓當前正在執行的線程休眠 }} catch (InterruptedException e) {}};Thread t = new Thread(r);// 分配新的 Thread 對象t.start();// 使線程開始執行 }} }SynchBankTest2 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();// 添加一個線程到等待集中System.out.print(Thread.currentThread());// 返回對當前正在執行的線程對象的引用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();// 解除等待線程的阻塞狀態 }/*** 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;} }Bank

測試程序3：

l?在Elipse環境下運行以下程序，結合程序運行結果分析程序存在問題；

l?嘗試解決程序中存在問題。

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();

??}

}

運行結果：

?

class Cbank {private static int s = 2000;public synchronized 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();} }

實驗2?編程練習

利用多線程及同步方法，編寫一個程序模擬火車票售票系統，共3個窗口，賣10張票，程序輸出結果類似（程序輸出不唯一，可以是其他類似結果）。

Thread-0窗口售：第1張票

Thread-0窗口售：第2張票

Thread-1窗口售：第3張票

Thread-2窗口售：第4張票

Thread-2窗口售：第5張票

Thread-1窗口售：第6張票

Thread-0窗口售：第7張票

Thread-2窗口售：第8張票

Thread-1窗口售：第9張票

Thread-0窗口售：第10張票

public class Demo {public static void main(String[] args) {Mythread mythread = new Mythread();Thread t1 = new Thread(mythread);Thread t2 = new Thread(mythread);Thread t3 = new Thread(mythread);t1.start();t2.start();t3.start();} }class Mythread implements Runnable {int t = 1;boolean flag = true;@Overridepublic void run() {// TODO Auto-generated method stubwhile (flag) {try {Thread.sleep(500);} catch (Exception e) {// TODO: handle exception e.printStackTrace();}synchronized (this) {if (t <= 10) {System.out.println(Thread.currentThread().getName() + "窗口售：第" + t + "張票");t++;}if (t > 10) {flag = false;}}}} }

三、實驗總結：

?

這次實驗比起前幾次來說不算難，完成得也比較輕松，接下來的時間主要是復習之前的知識，為期末考試做準備。

?

轉載于:https://www.cnblogs.com/xuezhiqian/p/10162933.html

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