UnsynchBankTest.java Source code

Introduction

Here is the source code for UnsynchBankTest.java

Source

/*
 This program is a part of the companion code for Core Java 8th ed.
 (http://horstmann.com/corejava)
    
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
    
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
    
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * This program shows data corruption when multiple threads access a data
 * structure.
 * 
 * @version 1.30 2004-08-01
 * @author Cay Horstmann
 */
public class UnsynchBankTest {
    public static void main(String[] args) {
        Bank b = new Bank(NACCOUNTS, INITIAL_BALANCE);
        int i;
        for (i = 0; i < NACCOUNTS; i++) {
            TransferRunnable r = new TransferRunnable(b, i, INITIAL_BALANCE);
            Thread t = new Thread(r);
            t.start();
        }
    }

    public static final int NACCOUNTS = 100;

    public static final double INITIAL_BALANCE = 1000;
}

/*
 * This program is a part of the companion code for Core Java 8th ed.
 * (http://horstmann.com/corejava)
 * 
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * this program. If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * A runnable that transfers money from an account to other accounts in a bank.
 * 
 * @version 1.30 2004-08-01
 * @author Cay Horstmann
 */
class TransferRunnable implements Runnable {
    /**
     * Constructs a transfer runnable.
     * 
     * @param b
     *          the bank between whose account money is transferred
     * @param from
     *          the account to transfer money from
     * @param max
     *          the maximum amount of money in each transfer
     */
    public TransferRunnable(Bank b, int from, double max) {
        bank = b;
        fromAccount = from;
        maxAmount = max;
    }

    public void run() {
        try {
            while (true) {
                int toAccount = (int) (bank.size() * Math.random());
                double amount = maxAmount * Math.random();
                bank.transfer(fromAccount, toAccount, amount);
                Thread.sleep((int) (DELAY * Math.random()));
            }
        } catch (InterruptedException e) {
        }
    }

    private Bank bank;

    private int fromAccount;

    private double maxAmount;

    private int DELAY = 10;
}

/*
 * This program is a part of the companion code for Core Java 8th ed.
 * (http://horstmann.com/corejava)
 * 
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * this program. If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * A bank with a number of bank accounts.
 * 
 * @version 1.30 2004-08-01
 * @author Cay Horstmann
 */
class Bank {
    /**
     * 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];
        for (int i = 0; i < accounts.length; i++)
            accounts[i] = 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 void transfer(int from, int to, double amount) {
        if (accounts[from] < amount)
            return;
        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());
    }

    /**
     * Gets the sum of all account balances.
     * 
     * @return the total balance
     */
    public 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;
    }

    private final double[] accounts;
}