Revert "add monitor design pattern (#1640 )"

This reverts commit c2786e5dc4a295ce771e79fce9b2e7fccf6fd0cc.
2021-10-19 20:29:20 +03:00
7 changed files with 0 additions and 294 deletions
--- a/monitor/README.md
+++ b/monitor/README.md
@ -1,71 +0,0 @@
 ---
 layout: pattern
 title: Monitor
 folder: monitor
 permalink: /patterns/monitor/
 categories: Concurrency
 language: en
 tags:
 - Performance
 ---
 ## Intent
 Monitor pattern is used to create thread-safe objects and prevent conflicts between threads in concurrent applications.
 ## Explanation
 In plain words
 > Monitor pattern is used to enforce single-threaded access to data. Only one thread at a time is allowed to execute code within the monitor object.
 Wikipedia says
 > In concurrent programming (also known as parallel programming), a monitor is a synchronization construct that allows threads to have both mutual exclusion and the ability to wait (block) for a certain condition to become false. Monitors also have a mechanism for signaling other threads that their condition has been met.
 **Programmatic Examples**
 Consider there is a bank that transfers money from an account to another account with transfer method . it is `synchronized` mean just one thread can access to this method because if many threads access to it and transfer money from an account to another account in same time balance changed !   
 ```
 class Bank {
     private int[] accounts;
     Logger logger;
     public Bank(int accountNum, int baseAmount, Logger logger) {
         this.logger = logger;
         accounts = new int[accountNum];
         Arrays.fill(accounts, baseAmount);
     }
     public synchronized void transfer(int accountA, int accountB, int amount) {
         if (accounts[accountA] >= amount) {
             accounts[accountB] += amount;
             accounts[accountA] -= amount;
             logger.info("Transferred from account :" + accountA + " to account :" + accountB + " , amount :" + amount + " . balance :" + getBalance());
         }
     }
 ```
 getBalance always return total amount and the total amount should be same after each transfers 
 ```
     private synchronized int getBalance() {
         int balance = 0;
         for (int account : accounts) {
             balance += account;
         }
         return balance;
     }
 }
 ```
 ## Class diagram
 ![alt text](./etc/monitor.urm.png "Monitor class diagram")
 ## Applicability
 Use the Monitor pattern when
 * we have a shared resource and there is critical section .
 * you want to create thread-safe objects .
 * you want to achieve mutual exclusion in high level programming language .
--- a/monitor/etc/monitor.urm.png
+++ b/monitor/etc/monitor.urm.png
--- a/monitor/etc/monitor.urm.puml
+++ b/monitor/etc/monitor.urm.puml
@ -1,12 +0,0 @@
@startuml
 Main - Bank : use
 class Main{
    + main(args : String[]) : void
 }
 class Bank{
    - accounts : int[]
    + Bank (accountNum : int , baseAccount : int)
    + transfer(accountA : int , accountB : int , amount : int) : void {synchronized}
    - getBalance() : void {synchronized}
 }
@enduml
--- a/monitor/pom.xml
+++ b/monitor/pom.xml
@ -1,59 +0,0 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!--
    The MIT License
    Copyright © 2014-2021 Ilkka Seppälä
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:
    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.
    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    THE SOFTWARE.
 -->
 <project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <artifactId>java-design-patterns</artifactId>
        <groupId>com.iluwatar</groupId>
        <version>1.24.0-SNAPSHOT</version>
    </parent>
    <artifactId>monitor</artifactId>
    <dependencies>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-engine</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <!-- Maven assembly plugin is invoked with default setting which we have
                in parent pom and specifying the class having main method -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-assembly-plugin</artifactId>
                <executions>
                    <execution>
                        <configuration>
                            <archive>
                                <manifest>
                                    <mainClass>com.iluwatar.abstractdocument.Main</mainClass>
                                </manifest>
                            </archive>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
 </project>
--- a/monitor/src/main/java/com/iluwatar/monitor/Bank.java
+++ b/monitor/src/main/java/com/iluwatar/monitor/Bank.java
@ -1,37 +0,0 @@
 package com.iluwatar.monitor;
 import java.util.Arrays;
 import java.util.logging.Logger;
 // Bank class implements the Monitor pattern
 public class Bank {
    private int[] accounts;
    Logger logger;
    public Bank(int accountNum, int baseAmount, Logger logger) {
        this.logger = logger;
        accounts = new int[accountNum];
        Arrays.fill(accounts, baseAmount);
    }
    public synchronized void transfer(int accountA, int accountB, int amount) {
        if (accounts[accountA] >= amount) {
            accounts[accountB] += amount;
            accounts[accountA] -= amount;
            logger.info("Transferred from account :" + accountA + " to account :" + accountB + " , amount :" + amount + " . balance :" + getBalance());
        }
    }
    public synchronized int getBalance() {
        int balance = 0;
        for (int account : accounts) {
            balance += account;
        }
        return balance;
    }
    public int[] getAccounts() {
        return accounts;
    }
 }
--- a/monitor/src/main/java/com/iluwatar/monitor/Main.java
+++ b/monitor/src/main/java/com/iluwatar/monitor/Main.java
@ -1,60 +0,0 @@
 /*
 * The MIT License
 * Copyright © 2014-2021 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 package com.iluwatar.monitor;
 import java.util.*;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.logging.Logger;
 /**
 * <p>The Monitor pattern is used in concurrent algorithms to achieve mutual exclusion.</p>
 *
 * <p>Bank is a simple class that transfers money from an account to another account using
 * {@link Bank#transfer}. It can also return the balance of the bank account stored in the bank.</p>
 *
 * <p>Main class uses ThreadPool to run threads that do transactions on the bank accounts.</p>
 */
 public class Main {
    public static void main(String[] args) {
        Logger logger = Logger.getLogger("monitor");
        var bank = new Bank(4, 1000, logger);
        Runnable runnable = () -> {
            try {
                Thread.sleep((long) (Math.random() * 1000));
                Random random = new Random();
                for (int i = 0; i < 1000000; i++)
                    bank.transfer(random.nextInt(4), random.nextInt(4), (int) (Math.random() * 1000));
            } catch (InterruptedException e) {
                logger.info(e.getMessage());
            }
        };
        ExecutorService executorService = Executors.newFixedThreadPool(5);
        for (int i = 0; i < 5; i++) {
            executorService.execute(runnable);
        }
    }
 }
--- a/monitor/src/main/test/java/com/iluwater/java/BankTest.java
+++ b/monitor/src/main/test/java/com/iluwater/java/BankTest.java
@ -1,55 +0,0 @@
 package com.iluwater.java;
 import com.iluwatar.monitor.Bank;
 import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 import static org.junit.jupiter.api.Assertions.*;
 import static org.junit.jupiter.api.Assumptions.*;
 import java.util.logging.Logger;
 public class BankTest {
    private static Bank bank;
    private static final int ACCOUNT_NUM = 4;
    private static final int BASE_AMOUNT = 1000;
    private static final Logger LOGGER = Logger.getLogger("monitor");
    @BeforeAll
    public static void Setup() {
        bank = new Bank(ACCOUNT_NUM, BASE_AMOUNT, LOGGER);
    }
    @Test
    public void GetAccountHaveNotBeNull() {
        assertNotNull(bank.getAccounts());
    }
    @Test
    public void LengthOfAccountsHaveToEqualsToAccountNumConstant() {
        assumeTrue(bank.getAccounts() != null);
        assertEquals(ACCOUNT_NUM, bank.getAccounts().length);
    }
    @Test
    public void TransferMethodHaveToTransferAmountFromAnAccountToOtherAccount() {
        bank.transfer(0, 1, 1000);
        int accounts[] = bank.getAccounts();
        assertEquals(0, accounts[0]);
        assertEquals(2000, 2000);
    }
    @Test
    public void BalanceHaveToBeOK() {
        assertEquals(4000, bank.getBalance());
    }
    @AfterAll
    public static void TearDown() {
        bank = null;
    }
 }