MULTITHREADING AND PARALLEL PROGRAMMING - Introduction to Java Programming: Comprehensive Version - page 1109

«interface»
java.lang.Runnable

100 1 1 1

AddAPennyTask

AccountWithoutSync Account

+run(): void -account: Account -balance: int

+main(args: String[]): void +getBalance(): int

+deposit(amount: int): void

F IGURE 30.9

AccountWithoutSync contains an instance of Account and 100 threads of AddAPennyTask .

L ISTING 30.4 AccountWithoutSync.java

1 import java.util.concurrent.*;
2
3 public class AccountWithoutSync {
4

private static Account account = new Account();

5
6 public static void main(String[] args) {

7 ExecutorService executor = Executors.newCachedThreadPool(); create executor

8
9 // Create and launch 100 threads

10 for ( int i = 0 ; i < 100 ; i++) {

11 executor.execute( new AddAPennyTask()); submit task

12 }
13
14

executor.shutdown();

shut down executor

15
16 // Wait until all tasks are finished
17 while (!executor.isTerminated()) {
18 }
19
20 System.out.println( "What is balance? " + account.getBalance());
21 }
22
23 // A thread for adding a penny to the account
24 private static class AddAPennyTask implements Runnable {
25 public void run() {
26 account.deposit( 1 );
27 }
28 }
29
30

wait for all tasks to terminate

// An inner class for account

31 private static class Account {

32 private int balance = 0 ;

33
34 public int getBalance() {

35 return balance;

36 }
37
38 public void deposit( int amount) {

39 int newBalance = balance + amount;

40
41 // This delay is deliberately added to magnify the