201771010118 馬昕璐 《面向對象設計 java》第十七周實驗總結
阿新 • • 發佈：2018-12-23
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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：測試程序並進行代碼註釋。
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; 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 //通過鎖對象生成條件對象 { bankLock.lock();//加鎖 try { while (accounts[from] < amount) sufficientFunds.await();//條件對象如果被註釋會出現死鎖現象不能實現線程的有效調用 System.out.print(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()); sufficientFunds.signalAll(); } finally { bankLock.unlock(); } } /** * Gets the sum of all account balances. * @return the total balance */ public double getTotalBalance() { bankLock.lock(); try { double sum = 0; for (double a : accounts) sum += a; return sum; } finally { bankLock.unlock(); } } /** * Gets the number of accounts in the bank. * @return the number of accounts */ public int size() { return accounts.length; } }
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())); } } catch (InterruptedException e) { } }; Thread t = new Thread(r); t.start(); } } }
實驗結果如下：
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; 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(); //在其他線程調用此對象的 notify() 方法或 notifyAll() 方法前，導致當前線程等待 System.out.print(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()); notifyAll();//喚醒在此對象監視器上等待的所有線程 } /** * 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; } }
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())); } } catch (InterruptedException e) { } }; Thread t = new Thread(r); t.start(); } } }
實驗結果如圖所示：
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。
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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(); } } |
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(); } }
實驗結果如下：
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; @Override public void run() { while(flag) { try { Thread.sleep(500); } catch (InterruptedException e) { // TODO Auto-generated catch block 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; } } } } }
實驗總結：在這周的理論學習部分中，我們學習了關於解決線程並發執行中的問題，實驗中掌握了利用鎖對象和條件對象實現的多線程同步技術。在一學期的java學習中我收獲了很多，對學長及老師的教導與幫助深表感謝。
201771010118 馬昕璐 《面向對象設計 java》第十七周實驗總結