Chain of responsibility design pattern

README.md

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-# DesignPatternsJava9
-This repo consists Gang of Four Design patterns code on Java 9. Each branch in the repository has code of 1 design pattern. Switch repository to try out different design patterns.
+# What is Command Design Pattern 
+Command encapsulate all information needed to perform an action. It allows the requester of a particular action to be decoupled from the object that performs the action.
+
+## Diagram
+![Diagram](https://github.com/premaseem/DesignPatternsJava9/blob/chain-of-responsibility/diagrams/template-method-Pattern-class-diagram.jpeg "Diagram")
+
+![Diagram](https://github.com/premaseem/DesignPatternsJava9/blob/chain-of-responsibility/diagrams/Template-method-Design-Pattern-generic.jpeg "Diagram")
+
+![Diagram](https://github.com/premaseem/DesignPatternsJava9/blob/chain-of-responsibility/diagrams/template-method-sequence.png "Diagram")
+
+### When to use Command Design Pattern 
+The invoker should be decoupled from the object handling the invocation.
+
+### Learn Design Patterns with Java by Aseem Jain
+This repository contains working project code used in video Course by Packt Publication with title "Learn Design Patterns with Java " authored by "Aseem Jain".
+
+### Course link: 
+https://www.packtpub.com/application-development/learn-design-patterns-java-9-video
+
+### ![ http://in.linkedin.com/in/premaseem](https://github.com/premaseem/DesignPatternsJava9/blob/master/linkedin.png "http://in.linkedin.com/in/premaseem") Profile:  http://in.linkedin.com/in/premaseem
+
+### Authors blog on design patterns:
+https://premaseem.wordpress.com/category/computers/design-patterns/
+
+### Software Design pattern community face book page:
+https://www.facebook.com/DesignPatternGuru/
+
+### Note: 
+* This code base will work on Java 9 and above versions. 
+* `diagrams` folders carry UML diagrams.
+* `pattern` folder has code of primary example. 
+* `patternBonus` folder has code of secondary or bonus example.

pattern/src/com/premaseem/ATMmoneyDispenser/Client.java

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+package com.premaseem.ATMmoneyDispenser;
+
+/*
+@author: Aseem Jain
+@title: Design Patterns with Java 9
+@link: https://premaseem.wordpress.com/category/computers/design-patterns/
+*/
+
+import java.util.Scanner;
+
+public class Client {
+
+	public static void main(String[] args) {
+
+		System.out.println("Welcome to ATM Money dispenser program designed using Chain of Responsibility");
+		Scanner scan = new Scanner(System.in);
+
+		MoneyChainHandler hundredDollarHandler_100 = new HundrenDollarHandler_100(100);
+		MoneyChainHandler fiftyDollarHandler_50 = new FiftyDollarHandler_50(50);
+		MoneyChainHandler tenDollarHandler_10 = new TenDollarHandler_10(10);
+		MoneyChainHandler fiveDollarHandler_5 = new FiveDollarHandler_5(5);
+		MoneyChainHandler twoDollarHandler_2 = new TwoDollarHandler_2(2);
+		MoneyChainHandler oneDollarHandler_1 = new OneDollarHandler_1(1);
+
+		// Setting up the change
+		hundredDollarHandler_100.setNextHandler(fiftyDollarHandler_50);
+		fiftyDollarHandler_50.setNextHandler(tenDollarHandler_10);
+		tenDollarHandler_10.setNextHandler(fiveDollarHandler_5);
+		fiveDollarHandler_5.setNextHandler(twoDollarHandler_2);
+		twoDollarHandler_2.setNextHandler(oneDollarHandler_1);
+
+		String repeatRunFlag = "y";
+		while (!repeatRunFlag.equalsIgnoreCase("no")) {
+			System.out.println("Please enter amount you want to withdraw eg 3450 ");
+			int choice = scan.nextInt();
+            hundredDollarHandler_100.handler(choice);
+
+			System.out.println("=============================");
+
+			System.out.println("Press No to Exit and any other character to repeat ....  ");
+			try {
+				repeatRunFlag = scan.next();
+			} catch (Exception e) {
+				repeatRunFlag = "n";
+			}
+		}
+
+		System.out.println("\n $$$$$$$$$$$$$$$$$$$$  Thanks by Prem Aseem $$$$$$$$$$$$$$$$$$$$$$ \n ");
+		System.out.println("\n $$$$$$$$$$$$$$$$$$$$$  www.premaseem.me  $$$$$$$$$$$$$$$$$$$$$$ \n ");
+
+	}
+}

pattern/src/com/premaseem/ATMmoneyDispenser/MoneyChainHandler.java

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+package com.premaseem.ATMmoneyDispenser;
+
+/*
+@author: Aseem Jain
+@title: Design Patterns with Java 9
+@link: https://premaseem.wordpress.com/category/computers/design-patterns/
+*/
+
+public abstract class MoneyChainHandler {
+    MoneyChainHandler nextHandler = null;
+    Integer noteDenomination = 0;
+
+    public MoneyChainHandler setNextHandler (MoneyChainHandler nextHandler) {
+        this.nextHandler = nextHandler;
+        return this.nextHandler;
+    }
+
+    public void handler (int dollarBill) {
+        int notes = dollarBill / noteDenomination;
+        int remainingAmount = dollarBill % noteDenomination;
+
+        if (notes > 0) {
+            System.out.printf("dispatched %d X %d = %d handled by %s \n", noteDenomination, notes, (noteDenomination * notes), this.getClass().getSimpleName());
+        }
+        if (nextHandler != null && remainingAmount > 0) {
+            nextHandler.handler(remainingAmount);
+        }
+    }
+
+}
+
+class HundrenDollarHandler_100 extends MoneyChainHandler {
+    public HundrenDollarHandler_100 (Integer noteDenomination) {
+        this.noteDenomination = noteDenomination;
+    }
+}
+
+class FiftyDollarHandler_50 extends MoneyChainHandler {
+    public FiftyDollarHandler_50 (Integer noteDenomination) {
+        this.noteDenomination = noteDenomination;
+    }
+}
+
+class TenDollarHandler_10 extends MoneyChainHandler {
+    public TenDollarHandler_10 (Integer noteDenomination) {
+        this.noteDenomination = noteDenomination;
+    }
+}
+
+class FiveDollarHandler_5 extends MoneyChainHandler {
+    public FiveDollarHandler_5 (Integer noteDenomination) {
+        this.noteDenomination = noteDenomination;
+    }
+}
+
+class TwoDollarHandler_2 extends MoneyChainHandler {
+    public TwoDollarHandler_2 (Integer noteDenomination) {
+        this.noteDenomination = noteDenomination;
+    }
+}
+
+class OneDollarHandler_1 extends MoneyChainHandler {
+    public OneDollarHandler_1 (Integer noteDenomination) {
+        this.noteDenomination = noteDenomination;
+    }
+}

patternBonus/src/com/premaseem/chainOfResponsibility/loggerProgram/ClientFileForLoggerProgram.java

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+package com.premaseem.chainOfResponsibility.loggerProgram;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Scanner;
+
+public class ClientFileForLoggerProgram {
+
+	public static void main(String[] args) {
+
+		System.out.println("Welcome to Logger program designed using Chain of Responsibility ");
+		Scanner scan = new Scanner(System.in);
+		LogHandler logHandler;
+		LogHandler allLogLevelHandler = new AllLogLevelHandler();
+		LogHandler debugLogHandler = new DebugLogHandler();
+		LogHandler errorLogHandler = new ErrorLogHandler();
+		LogHandler fatalLogHandler = new FatalLogHandler();
+		LogHandler criticalLogHandler = new CriticalLogHandler();
+
+		// Setting up the chain
+		allLogLevelHandler.setNextHandler(debugLogHandler);
+		debugLogHandler.setNextHandler(errorLogHandler);
+		errorLogHandler.setNextHandler(fatalLogHandler);
+		fatalLogHandler.setNextHandler(criticalLogHandler);
+
+		// Log level priority, high rank covers all below handlers
+		List<LogHandler> logHandlers = new ArrayList<LogHandler>(10);
+		logHandlers.add(0,allLogLevelHandler);
+		logHandlers.add(1,debugLogHandler);
+        logHandlers.add(2,errorLogHandler);
+        logHandlers.add(3,fatalLogHandler);
+        logHandlers.add(4,criticalLogHandler);
+
+		String repeatRunFlag = "y";
+		while (!repeatRunFlag.equalsIgnoreCase("no")) {
+			System.out.println("Please enter message to be logged ");
+			String message = scan.next();
+			System.out.println("Please choose the level from 1 to 5 for logging ");
+			System.out.println("INFO(5),		DEBUG(4),		ERROR(3),		FATAL(2),		CRITICAL(1)");
+			try{
+			int choice = scan.nextInt();
+				logHandler = logHandlers.get(choice);
+			}catch (Exception e){
+				logHandler = logHandlers.get(0);
+			}
+
+			logHandler.handler(message);
+
+			System.out.println("=============================");
+
+			System.out.println("Press No to Exit and any other character to repeat ....  ");
+			try {
+				repeatRunFlag = scan.next();
+			} catch (Exception e) {
+				repeatRunFlag = "n";
+			}
+		}
+
+		System.out.println("\n $$$$$$$$$$$$$$$$$$$$  Thanks by Prem Aseem $$$$$$$$$$$$$$$$$$$$$$ \n ");
+		System.out.println("\n $$$$$$$$$$$$$$$$$$$$$  www.premaseem.me  $$$$$$$$$$$$$$$$$$$$$$ \n ");
+	}
+}

patternBonus/src/com/premaseem/chainOfResponsibility/loggerProgram/LogHandler.java

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+package com.premaseem.chainOfResponsibility.loggerProgram;
+
+public abstract class LogHandler {
+
+
+	public enum LOG_LEVEL {
+		INFO(5),
+		DEBUG(4),
+		ERROR(3),
+		FATAL(2),
+		CRITICAL(1);
+
+		Integer priority =1;
+		 LOG_LEVEL(int priorityLevel){
+			 priority = priorityLevel;
+		}
+	}
+
+	LogHandler nextHandler = null;
+
+	public void setNextHandler(LogHandler nextHandler) {
+		this.nextHandler = nextHandler;
+	}
+
+	public void handler(String message) {
+			System.out.printf(" %s console is printing message = %S \n " , this.getClass().getSimpleName(), message );
+		if(nextHandler !=null){
+			nextHandler.handler(message);
+		}
+	}
+}
+
+class AllLogLevelHandler extends LogHandler{
+
+}
+
+class DebugLogHandler extends LogHandler{
+
+}
+
+class ErrorLogHandler extends LogHandler{
+
+}
+
+class FatalLogHandler extends LogHandler{
+
+}
+
+class CriticalLogHandler extends LogHandler{
+
+}

patternBonus/src/com/premaseem/chainOfResponsibility/numberHandler/Client.java

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+package com.premaseem.chainOfResponsibility.numberHandler;
+
+/*
+@author: Aseem Jain
+@title: Design Patterns with Java 9
+@link: https://premaseem.wordpress.com/category/computers/design-patterns/
+*/
+
+import java.util.Scanner;
+
+public class Client {
+
+	public static void main(String[] args) {
+
+		System.out.println("Welcome to Number identifier program designed using Chain of Responsibility ");
+		Scanner scan = new Scanner(System.in);
+
+		NumberChain positiveNumberHandler = new PositiveNumberHandler();
+		NumberChain negativeNumberHandler = new NegativeNumberHandler();
+		NumberChain neutralNumberHandler = new ZeroNumberHandler();
+
+		// Setting up the chain
+		positiveNumberHandler.setNextHandler(negativeNumberHandler);
+		negativeNumberHandler.setNextHandler(neutralNumberHandler);
+
+		String repeatRunFlag = "y";
+		while (!repeatRunFlag.equalsIgnoreCase("no")) {
+			System.out.println("Please enter any number 0, less then or greater then zero eg. -22 or 89 ? ");
+			int choice = scan.nextInt();
+			positiveNumberHandler.handler(choice);
+
+			System.out.println("=============================");
+
+			System.out.println("Press No to Exit and any other character to repeat ....  ");
+			try {
+				repeatRunFlag = scan.next();
+			} catch (Exception e) {
+				repeatRunFlag = "n";
+			}
+		}
+
+		System.out.println("\n $$$$$$$$$$$$$$$$$$$$  Thanks by Prem Aseem $$$$$$$$$$$$$$$$$$$$$$ \n ");
+		System.out.println("\n $$$$$$$$$$$$$$$$$$$$$  www.premaseem.me  $$$$$$$$$$$$$$$$$$$$$$ \n ");
+
+	}
+}

patternBonus/src/com/premaseem/chainOfResponsibility/numberHandler/NumberChain.java

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+package com.premaseem.chainOfResponsibility.numberHandler;
+
+public abstract class NumberChain {
+
+	NumberChain nextHandler = null;
+
+	public NumberChain setNextHandler(NumberChain nextHandler) {
+		this.nextHandler = nextHandler;
+		return this.nextHandler;
+	}
+
+	public abstract void handler(int requestNumber);
+
+}
+
+class PositiveNumberHandler extends NumberChain {
+
+	@Override
+	public void handler(int requestNumber) {
+		if (requestNumber > 0) {
+			System.out.println(this.getClass().getSimpleName() +" handled number " + requestNumber);
+		}else{
+			if(nextHandler!=null)
+			nextHandler.handler(requestNumber);
+		}
+	}
+}
+
+class NegativeNumberHandler extends NumberChain {
+
+	@Override
+	public void handler(int requestNumber) {
+		if (requestNumber < 0) {
+			System.out.println(this.getClass().getSimpleName() +" handled number " + requestNumber);
+		}else{
+			if(nextHandler!=null)
+			nextHandler.handler(requestNumber);
+		}
+	}
+}
+
+class ZeroNumberHandler extends NumberChain {
+
+	@Override
+	public void handler(int requestNumber) {
+		if (requestNumber == 0) {
+			System.out.println(this.getClass().getSimpleName() +" handled number " + requestNumber);
+		}else{
+			if(nextHandler!=null)
+			nextHandler.handler(requestNumber);
+		}
+	}
+}