Merge branch 'master' into business-delegate-explanation

.all-contributorsrc

@@ -1440,16 +1440,6 @@
       "contributions": [
         "doc"
       ]
-    },
-    {
-      "login": "jinishavora",
-      "name": "jinishavora",
-      "avatar_url": "https://avatars.githubusercontent.com/u/40777762?v=4",
-      "profile": "https://www.linkedin.com/in/jinisha-vora",
-      "contributions": [
-        "review",
-        "code"
-      ]
     }
   ],
   "contributorsPerLine": 4,

.github/workflows/maven-pr-builder.yml

@@ -29,7 +29,7 @@ name: Java PR Builder
 on:
   pull_request:
     branches: [ master ]
-    types: [ opened, reopened, synchronize ]
+    types: [ opened, reopened, synchronize, labeled, unlabeled ]
 
 jobs:
   build:

README.md

@@ -10,7 +10,7 @@
 [![Coverage](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=coverage)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
 [![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 <!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-159-orange.svg?style=flat-square)](#contributors-)
+[![All Contributors](https://img.shields.io/badge/all_contributors-158-orange.svg?style=flat-square)](#contributors-)
 <!-- ALL-CONTRIBUTORS-BADGE:END -->
 
 <br/>
@@ -312,7 +312,6 @@ This project is licensed under the terms of the MIT license.
   <tr>
     <td align="center"><a href="https://github.com/noamgrinch"><img src="https://avatars.githubusercontent.com/u/31648669?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Noam Greenshtain</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=noamgrinch" title="Code">💻</a></td>
     <td align="center"><a href="https://xuyonghong.cn/"><img src="https://avatars.githubusercontent.com/u/14086462?v=4?s=100" width="100px;" alt=""/><br /><sub><b>yonghong Xu</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=qfxl" title="Documentation">📖</a></td>
-    <td align="center"><a href="https://www.linkedin.com/in/jinisha-vora"><img src="https://avatars.githubusercontent.com/u/40777762?v=4?s=100" width="100px;" alt=""/><br /><sub><b>jinishavora</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Ajinishavora" title="Reviewed Pull Requests">👀</a> <a href="https://github.com/iluwatar/java-design-patterns/commits?author=jinishavora" title="Code">💻</a></td>
   </tr>
 </table>
 

bytecode/README.md

@@ -9,234 +9,18 @@ tags:
 ---
 
 ## Intent
-
+Allows to encode behaviour as instructions for virtual machine.
-Allows encoding behavior as instructions for a virtual machine.
-
-## Explanation
-
-Real world example
-
-> A team is working on a new game where wizards battle against each other. The wizard behavior 
-> needs to be carefully adjusted and iterated hundreds of times through playtesting. It's not 
-> optimal to ask the programmer to make changes each time the game designer wants to vary the 
-> behavior, so the wizard behavior is implemented as a data-driven virtual machine.
-
-In plain words
-
-> Bytecode pattern enables behavior driven by data instead of code.
-
-[Gameprogrammingpatterns.com](https://gameprogrammingpatterns.com/bytecode.html) documentation 
-states:
-
-> An instruction set defines the low-level operations that can be performed. A series of 
-> instructions is encoded as a sequence of bytes. A virtual machine executes these instructions one 
-> at a time, using a stack for intermediate values. By combining instructions, complex high-level 
-> behavior can be defined.
-
-**Programmatic Example**
-
-One of the most important game objects is the `Wizard` class.
-
-```java
-@AllArgsConstructor
-@Setter
-@Getter
-@Slf4j
-public class Wizard {
-
-  private int health;
-  private int agility;
-  private int wisdom;
-  private int numberOfPlayedSounds;
-  private int numberOfSpawnedParticles;
-
-  public void playSound() {
-    LOGGER.info("Playing sound");
-    numberOfPlayedSounds++;
-  }
-
-  public void spawnParticles() {
-    LOGGER.info("Spawning particles");
-    numberOfSpawnedParticles++;
-  }
-}
-```
-
-Next, we show the available instructions for our virtual machine. Each of the instructions has its 
-own semantics on how it operates with the stack data. For example, the ADD instruction takes the top
-two items from the stack, adds them together and pushes the result to the stack.
-
-```java
-@AllArgsConstructor
-@Getter
-public enum Instruction {
-
-  LITERAL(1),         // e.g. "LITERAL 0", push 0 to stack
-  SET_HEALTH(2),      // e.g. "SET_HEALTH", pop health and wizard number, call set health
-  SET_WISDOM(3),      // e.g. "SET_WISDOM", pop wisdom and wizard number, call set wisdom
-  SET_AGILITY(4),     // e.g. "SET_AGILITY", pop agility and wizard number, call set agility
-  PLAY_SOUND(5),      // e.g. "PLAY_SOUND", pop value as wizard number, call play sound
-  SPAWN_PARTICLES(6), // e.g. "SPAWN_PARTICLES", pop value as wizard number, call spawn particles
-  GET_HEALTH(7),      // e.g. "GET_HEALTH", pop value as wizard number, push wizard's health
-  GET_AGILITY(8),     // e.g. "GET_AGILITY", pop value as wizard number, push wizard's agility
-  GET_WISDOM(9),      // e.g. "GET_WISDOM", pop value as wizard number, push wizard's wisdom
-  ADD(10),            // e.g. "ADD", pop 2 values, push their sum
-  DIVIDE(11);         // e.g. "DIVIDE", pop 2 values, push their division
-  // ...
-}
-```
-
-At the heart of our example is the `VirtualMachine` class. It takes instructions as input and
-executes them to provide the game object behavior.
-
-```java
-@Getter
-@Slf4j
-public class VirtualMachine {
-
-  private final Stack<Integer> stack = new Stack<>();
-
-  private final Wizard[] wizards = new Wizard[2];
-
-  public VirtualMachine() {
-    wizards[0] = new Wizard(randomInt(3, 32), randomInt(3, 32), randomInt(3, 32),
-        0, 0);
-    wizards[1] = new Wizard(randomInt(3, 32), randomInt(3, 32), randomInt(3, 32),
-        0, 0);
-  }
-
-  public VirtualMachine(Wizard wizard1, Wizard wizard2) {
-    wizards[0] = wizard1;
-    wizards[1] = wizard2;
-  }
-
-  public void execute(int[] bytecode) {
-    for (var i = 0; i < bytecode.length; i++) {
-      Instruction instruction = Instruction.getInstruction(bytecode[i]);
-      switch (instruction) {
-        case LITERAL:
-          // Read the next byte from the bytecode.
-          int value = bytecode[++i];
-          // Push the next value to stack
-          stack.push(value);
-          break;
-        case SET_AGILITY:
-          var amount = stack.pop();
-          var wizard = stack.pop();
-          setAgility(wizard, amount);
-          break;
-        case SET_WISDOM:
-          amount = stack.pop();
-          wizard = stack.pop();
-          setWisdom(wizard, amount);
-          break;
-        case SET_HEALTH:
-          amount = stack.pop();
-          wizard = stack.pop();
-          setHealth(wizard, amount);
-          break;
-        case GET_HEALTH:
-          wizard = stack.pop();
-          stack.push(getHealth(wizard));
-          break;
-        case GET_AGILITY:
-          wizard = stack.pop();
-          stack.push(getAgility(wizard));
-          break;
-        case GET_WISDOM:
-          wizard = stack.pop();
-          stack.push(getWisdom(wizard));
-          break;
-        case ADD:
-          var a = stack.pop();
-          var b = stack.pop();
-          stack.push(a + b);
-          break;
-        case DIVIDE:
-          a = stack.pop();
-          b = stack.pop();
-          stack.push(b / a);
-          break;
-        case PLAY_SOUND:
-          wizard = stack.pop();
-          getWizards()[wizard].playSound();
-          break;
-        case SPAWN_PARTICLES:
-          wizard = stack.pop();
-          getWizards()[wizard].spawnParticles();
-          break;
-        default:
-          throw new IllegalArgumentException("Invalid instruction value");
-      }
-      LOGGER.info("Executed " + instruction.name() + ", Stack contains " + getStack());
-    }
-  }
-
-  public void setHealth(int wizard, int amount) {
-    wizards[wizard].setHealth(amount);
-  }
-  // other setters ->
-  // ...
-}
-```
-
-Now we can show the full example utilizing the virtual machine.
-
-```java
-  public static void main(String[] args) {
-
-    var vm = new VirtualMachine(
-        new Wizard(45, 7, 11, 0, 0),
-        new Wizard(36, 18, 8, 0, 0));
-
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("GET_HEALTH"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("GET_AGILITY"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("GET_WISDOM"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("ADD"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 2"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("DIVIDE"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("ADD"));
-    vm.execute(InstructionConverterUtil.convertToByteCode("SET_HEALTH"));
-  }
-```
-
-Here is the console output.
-
-```
-16:20:10.193 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed LITERAL, Stack contains [0]
-16:20:10.196 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed LITERAL, Stack contains [0, 0]
-16:20:10.197 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed GET_HEALTH, Stack contains [0, 45]
-16:20:10.197 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed LITERAL, Stack contains [0, 45, 0]
-16:20:10.197 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed GET_AGILITY, Stack contains [0, 45, 7]
-16:20:10.197 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed LITERAL, Stack contains [0, 45, 7, 0]
-16:20:10.197 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed GET_WISDOM, Stack contains [0, 45, 7, 11]
-16:20:10.197 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed ADD, Stack contains [0, 45, 18]
-16:20:10.197 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed LITERAL, Stack contains [0, 45, 18, 2]
-16:20:10.198 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed DIVIDE, Stack contains [0, 45, 9]
-16:20:10.198 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed ADD, Stack contains [0, 54]
-16:20:10.198 [main] INFO com.iluwatar.bytecode.VirtualMachine - Executed SET_HEALTH, Stack contains []
-```
 
 ## Class diagram
-
 ![alt text](./etc/bytecode.urm.png "Bytecode class diagram")
 
 ## Applicability
-
 Use the Bytecode pattern when you have a lot of behavior you need to define and your
 game’s implementation language isn’t a good fit because:
 
-* It’s too low-level, making it tedious or error-prone to program in.
+* it’s too low-level, making it tedious or error-prone to program in.
-* Iterating on it takes too long due to slow compile times or other tooling issues.
+* iterating on it takes too long due to slow compile times or other tooling issues.
-* It has too much trust. If you want to ensure the behavior being defined can’t break the game, you need to sandbox it from the rest of the codebase.
+* it has too much trust. If you want to ensure the behavior being defined can’t break the game, you need to sandbox it from the rest of the codebase.
-
-## Related patterns
-
-* [Interpreter](https://java-design-patterns.com/patterns/interpreter/)
 
 ## Credits
 

bytecode/etc/bytecode.ucls

@@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<class-diagram version="1.2.3" icons="true" always-add-relationships="false" generalizations="true" realizations="true" 
+  associations="true" dependencies="false" nesting-relationships="true" router="FAN">  
+  <class id="1" language="java" name="com.iluwatar.bytecode.VirtualMachine" project="bytecode" 
+    file="/bytecode/src/main/java/com/iluwatar/bytecode/VirtualMachine.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="455" y="173"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="2" language="java" name="com.iluwatar.bytecode.App" project="bytecode" 
+    file="/bytecode/src/main/java/com/iluwatar/bytecode/App.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="148" y="110"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <class id="3" language="java" name="com.iluwatar.bytecode.Wizard" project="bytecode" 
+    file="/bytecode/src/main/java/com/iluwatar/bytecode/Wizard.java" binary="false" corner="BOTTOM_RIGHT">    
+    <position height="-1" width="-1" x="148" y="416"/>    
+    <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+      sort-features="false" accessors="true" visibility="true">      
+      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <operations public="true" package="true" protected="true" private="true" static="true"/>    
+    </display>  
+  </class>  
+  <association id="4">    
+    <end type="SOURCE" refId="1" navigable="false" variant="ASSOCIATION">      
+      <attribute id="5" name="wizards">        
+        <position height="18" width="48" x="296" y="291"/>      
+      </attribute>      
+      <multiplicity id="6" minimum="0" maximum="2147483647">        
+        <position height="0" width="0" x="-327" y="-27"/>      
+      </multiplicity>    
+    </end>    
+    <end type="TARGET" refId="3" navigable="true" variant="ASSOCIATION"/>    
+    <display labels="true" multiplicity="true"/>  
+  </association>  
+  <classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
+    sort-features="false" accessors="true" visibility="true">    
+    <attributes public="true" package="true" protected="true" private="true" static="true"/>    
+    <operations public="true" package="true" protected="true" private="true" static="true"/>  
+  </classifier-display>  
+  <association-display labels="true" multiplicity="true"/>
+</class-diagram>

bytecode/etc/bytecode.urm.puml

@@ -3,6 +3,7 @@ package com.iluwatar.bytecode {
   class App {
     - LOGGER : Logger {static}
     + App()
+    - interpretInstruction(instruction : String, vm : VirtualMachine) {static}
     + main(args : String[]) {static}
   }
   enum Instruction {
@@ -17,25 +18,22 @@ package com.iluwatar.bytecode {
     + SET_HEALTH {static}
     + SET_WISDOM {static}
     + SPAWN_PARTICLES {static}
-    - intValue : int
+    - value : int
     + getInstruction(value : int) : Instruction {static}
     + getIntValue() : int
     + valueOf(name : String) : Instruction {static}
     + values() : Instruction[] {static}
   }
   class VirtualMachine {
-    - LOGGER : Logger {static}
     - stack : Stack<Integer>
     - wizards : Wizard[]
     + VirtualMachine()
-    + VirtualMachine(wizard1 : Wizard, wizard2 : Wizard)
     + execute(bytecode : int[])
     + getAgility(wizard : int) : int
     + getHealth(wizard : int) : int
     + getStack() : Stack<Integer>
     + getWisdom(wizard : int) : int
     + getWizards() : Wizard[]
-    - randomInt(min : int, max : int) : int
     + setAgility(wizard : int, amount : int)
     + setHealth(wizard : int, amount : int)
     + setWisdom(wizard : int, amount : int)
@@ -47,7 +45,7 @@ package com.iluwatar.bytecode {
     - numberOfPlayedSounds : int
     - numberOfSpawnedParticles : int
     - wisdom : int
-    + Wizard(health : int, agility : int, wisdom : int, numberOfPlayedSounds : int, numberOfSpawnedParticles : int)
+    + Wizard()
     + getAgility() : int
     + getHealth() : int
     + getNumberOfPlayedSounds() : int
@@ -56,8 +54,6 @@ package com.iluwatar.bytecode {
     + playSound()
     + setAgility(agility : int)
     + setHealth(health : int)
-    + setNumberOfPlayedSounds(numberOfPlayedSounds : int)
-    + setNumberOfSpawnedParticles(numberOfSpawnedParticles : int)
     + setWisdom(wisdom : int)
     + spawnParticles()
   }

bytecode/src/main/java/com/iluwatar/bytecode/App.java

@@ -49,21 +49,33 @@ public class App {
    */
   public static void main(String[] args) {
 
-    var vm = new VirtualMachine(
+    var wizard = new Wizard();
-        new Wizard(45, 7, 11, 0, 0),
+    wizard.setHealth(45);
-        new Wizard(36, 18, 8, 0, 0));
+    wizard.setAgility(7);
+    wizard.setWisdom(11);
 
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
+    var vm = new VirtualMachine();
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
+    vm.getWizards()[0] = wizard;
-    vm.execute(InstructionConverterUtil.convertToByteCode("GET_HEALTH"));
+
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
+    String literal = "LITERAL 0";
-    vm.execute(InstructionConverterUtil.convertToByteCode("GET_AGILITY"));
+
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 0"));
+    interpretInstruction(literal, vm);
-    vm.execute(InstructionConverterUtil.convertToByteCode("GET_WISDOM"));
+    interpretInstruction(literal, vm);
-    vm.execute(InstructionConverterUtil.convertToByteCode("ADD"));
+    interpretInstruction("GET_HEALTH", vm);
-    vm.execute(InstructionConverterUtil.convertToByteCode("LITERAL 2"));
+    interpretInstruction(literal, vm);
-    vm.execute(InstructionConverterUtil.convertToByteCode("DIVIDE"));
+    interpretInstruction("GET_AGILITY", vm);
-    vm.execute(InstructionConverterUtil.convertToByteCode("ADD"));
+    interpretInstruction(literal, vm);
-    vm.execute(InstructionConverterUtil.convertToByteCode("SET_HEALTH"));
+    interpretInstruction("GET_WISDOM ", vm);
+    interpretInstruction("ADD", vm);
+    interpretInstruction("LITERAL 2", vm);
+    interpretInstruction("DIVIDE", vm);
+    interpretInstruction("ADD", vm);
+    interpretInstruction("SET_HEALTH", vm);
+  }
+
+  private static void interpretInstruction(String instruction, VirtualMachine vm) {
+    vm.execute(InstructionConverterUtil.convertToByteCode(instruction));
+    var stack = vm.getStack();
+    LOGGER.info(instruction + String.format("%" + (12 - instruction.length()) + "s", "") + stack);
   }
 }

bytecode/src/main/java/com/iluwatar/bytecode/Instruction.java

@@ -33,17 +33,17 @@ import lombok.Getter;
 @Getter
 public enum Instruction {
 
-  LITERAL(1),         // e.g. "LITERAL 0", push 0 to stack
+  LITERAL(1),
-  SET_HEALTH(2),      // e.g. "SET_HEALTH", pop health and wizard number, call set health
+  SET_HEALTH(2),
-  SET_WISDOM(3),      // e.g. "SET_WISDOM", pop wisdom and wizard number, call set wisdom
+  SET_WISDOM(3),
-  SET_AGILITY(4),     // e.g. "SET_AGILITY", pop agility and wizard number, call set agility
+  SET_AGILITY(4),
-  PLAY_SOUND(5),      // e.g. "PLAY_SOUND", pop value as wizard number, call play sound
+  PLAY_SOUND(5),
-  SPAWN_PARTICLES(6), // e.g. "SPAWN_PARTICLES", pop value as wizard number, call spawn particles
+  SPAWN_PARTICLES(6),
-  GET_HEALTH(7),      // e.g. "GET_HEALTH", pop value as wizard number, push wizard's health
+  GET_HEALTH(7),
-  GET_AGILITY(8),     // e.g. "GET_AGILITY", pop value as wizard number, push wizard's agility
+  GET_AGILITY(8),
-  GET_WISDOM(9),      // e.g. "GET_WISDOM", pop value as wizard number, push wizard's wisdom
+  GET_WISDOM(9),
-  ADD(10),            // e.g. "ADD", pop 2 values, push their sum
+  ADD(10),
-  DIVIDE(11);         // e.g. "DIVIDE", pop 2 values, push their division
+  DIVIDE(11);
 
   private final int intValue;
 

bytecode/src/main/java/com/iluwatar/bytecode/VirtualMachine.java

@@ -24,15 +24,12 @@
 package com.iluwatar.bytecode;
 
 import java.util.Stack;
-import java.util.concurrent.ThreadLocalRandom;
 import lombok.Getter;
-import lombok.extern.slf4j.Slf4j;
 
 /**
  * Implementation of virtual machine.
  */
 @Getter
-@Slf4j
 public class VirtualMachine {
 
   private final Stack<Integer> stack = new Stack<>();
@@ -40,21 +37,12 @@ public class VirtualMachine {
   private final Wizard[] wizards = new Wizard[2];
 
   /**
-   * No-args constructor.
+   * Constructor.
    */
   public VirtualMachine() {
-    wizards[0] = new Wizard(randomInt(3, 32), randomInt(3, 32), randomInt(3, 32),
+    for (var i = 0; i < wizards.length; i++) {
-        0, 0);
+      wizards[i] = new Wizard();
-    wizards[1] = new Wizard(randomInt(3, 32), randomInt(3, 32), randomInt(3, 32),
+    }
-        0, 0);
-  }
-
-  /**
-   * Constructor taking the wizards as arguments.
-   */
-  public VirtualMachine(Wizard wizard1, Wizard wizard2) {
-    wizards[0] = wizard1;
-    wizards[1] = wizard2;
   }
 
   /**
@@ -69,7 +57,6 @@ public class VirtualMachine {
         case LITERAL:
           // Read the next byte from the bytecode.
           int value = bytecode[++i];
-          // Push the next value to stack
           stack.push(value);
           break;
         case SET_AGILITY:
@@ -120,7 +107,6 @@ public class VirtualMachine {
         default:
           throw new IllegalArgumentException("Invalid instruction value");
       }
-      LOGGER.info("Executed " + instruction.name() + ", Stack contains " + getStack());
     }
   }
 
@@ -147,8 +133,4 @@ public class VirtualMachine {
   public int getAgility(int wizard) {
     return wizards[wizard].getAgility();
   }
-
-  private int randomInt(int min, int max) {
-    return ThreadLocalRandom.current().nextInt(min, max + 1);
-  }
 }

bytecode/src/main/java/com/iluwatar/bytecode/Wizard.java

@@ -23,7 +23,6 @@
 
 package com.iluwatar.bytecode;
 
-import lombok.AllArgsConstructor;
 import lombok.Getter;
 import lombok.Setter;
 import lombok.extern.slf4j.Slf4j;
@@ -32,15 +31,16 @@ import lombok.extern.slf4j.Slf4j;
  * This class represent game objects which properties can be changed by instructions interpreted by
  * virtual machine.
  */
-@AllArgsConstructor
 @Setter
 @Getter
 @Slf4j
 public class Wizard {
 
   private int health;
+
   private int agility;
   private int wisdom;
+
   private int numberOfPlayedSounds;
   private int numberOfSpawnedParticles;
 
@@ -53,4 +53,5 @@ public class Wizard {
     LOGGER.info("Spawning particles");
     numberOfSpawnedParticles++;
   }
+
 }

bytecode/src/main/java/com/iluwatar/bytecode/util/InstructionConverterUtil.java

@@ -73,4 +73,6 @@ public class InstructionConverterUtil {
       return false;
     }
   }
+
+
 }

caching/README.md

@@ -10,326 +10,20 @@ tags:
 ---
 
 ## Intent
-
+To avoid expensive re-acquisition of resources by not releasing
-The caching pattern avoids expensive re-acquisition of resources by not releasing them immediately 
+the resources immediately after their use. The resources retain their identity, are kept in some
-after use. The resources retain their identity, are kept in some fast-access storage, and are 
+fast-access storage, and are re-used to avoid having to acquire them again.
-re-used to avoid having to acquire them again.
-
-## Explanation
-
-Real world example
-
-> A team is working on a website that provides new homes for abandoned cats. People can post their
-> cats on the website after registering, but all the new posts require approval from one of the
-> site moderators. The user accounts of the site moderators contain a specific flag and the data
-> is stored in a MongoDB database. Checking for the moderator flag each time a post is viewed 
-> becomes expensive and it's a good idea to utilize caching here.
-
-In plain words
-
-> Caching pattern keeps frequently needed data in fast-access storage to improve performance.
-
-Wikipedia says:
-
-> In computing, a cache is a hardware or software component that stores data so that future 
-> requests for that data can be served faster; the data stored in a cache might be the result of 
-> an earlier computation or a copy of data stored elsewhere. A cache hit occurs when the requested 
-> data can be found in a cache, while a cache miss occurs when it cannot. Cache hits are served by 
-> reading data from the cache, which is faster than recomputing a result or reading from a slower 
-> data store; thus, the more requests that can be served from the cache, the faster the system 
-> performs.
-
-**Programmatic Example**
-
-Let's first look at the data layer of our application. The interesting classes are `UserAccount`
-which is a simple Java object containing the user account details, and `DbManager` which handles
-reading and writing of these objects to/from MongoDB database.
-
-```java
-@Setter
-@Getter
-@AllArgsConstructor
-@ToString
-public class UserAccount {
-  private String userId;
-  private String userName;
-  private String additionalInfo;
-}
-
-@Slf4j
-public final class DbManager {
-
-  private static MongoClient mongoClient;
-  private static MongoDatabase db;
-
-  private DbManager() { /*...*/ }
-
-  public static void createVirtualDb() { /*...*/ }
-
-  public static void connect() throws ParseException { /*...*/ }
-
-  public static UserAccount readFromDb(String userId) { /*...*/ }
-
-  public static void writeToDb(UserAccount userAccount) { /*...*/ }
-
-  public static void updateDb(UserAccount userAccount) { /*...*/ }
-
-  public static void upsertDb(UserAccount userAccount) { /*...*/ }
-}
-```
-
-In the example, we are demonstrating various different caching policies
-
-* Write-through writes data to the cache and DB in a single transaction
-* Write-around writes data immediately into the DB instead of the cache
-* Write-behind writes data into the cache initially whilst the data is only written into the DB 
-  when the cache is full
-* Cache-aside pushes the responsibility of keeping the data synchronized in both data sources to 
-  the application itself
-* Read-through strategy is also included in the aforementioned strategies and it returns data from 
-  the cache to the caller if it exists, otherwise queries from DB and stores it into the cache for 
-  future use.
-  
-The cache implementation in `LruCache` is a hash table accompanied by a doubly 
-linked-list. The linked-list helps in capturing and maintaining the LRU data in the cache. When 
-data is queried (from the cache), added (to the cache), or updated, the data is moved to the front 
-of the list to depict itself as the most-recently-used data. The LRU data is always at the end of 
-the list.
-
-```java
-@Slf4j
-public class LruCache {
-
-  static class Node {
-    String userId;
-    UserAccount userAccount;
-    Node previous;
-    Node next;
-
-    public Node(String userId, UserAccount userAccount) {
-      this.userId = userId;
-      this.userAccount = userAccount;
-    }
-  }
-  
-  /* ... omitted details ... */
-
-  public LruCache(int capacity) {
-    this.capacity = capacity;
-  }
-
-  public UserAccount get(String userId) {
-    if (cache.containsKey(userId)) {
-      var node = cache.get(userId);
-      remove(node);
-      setHead(node);
-      return node.userAccount;
-    }
-    return null;
-  }
-
-  public void set(String userId, UserAccount userAccount) {
-    if (cache.containsKey(userId)) {
-      var old = cache.get(userId);
-      old.userAccount = userAccount;
-      remove(old);
-      setHead(old);
-    } else {
-      var newNode = new Node(userId, userAccount);
-      if (cache.size() >= capacity) {
-        LOGGER.info("# Cache is FULL! Removing {} from cache...", end.userId);
-        cache.remove(end.userId); // remove LRU data from cache.
-        remove(end);
-        setHead(newNode);
-      } else {
-        setHead(newNode);
-      }
-      cache.put(userId, newNode);
-    }
-  }
-
-  public boolean contains(String userId) {
-    return cache.containsKey(userId);
-  }
-  
-  public void remove(Node node) { /* ... */ }
-  public void setHead(Node node) { /* ... */ }
-  public void invalidate(String userId) { /* ... */ }
-  public boolean isFull() { /* ... */ }
-  public UserAccount getLruData() { /* ... */ }
-  public void clear() { /* ... */ }
-  public List<UserAccount> getCacheDataInListForm() { /* ... */ }
-  public void setCapacity(int newCapacity) { /* ... */ }
-}
-```
-
-The next layer we are going to look at is `CacheStore` which implements the different caching
-strategies.
-
-```java
-@Slf4j
-public class CacheStore {
-
-  private static LruCache cache;
-
-  /* ... details omitted ... */
-
-  public static UserAccount readThrough(String userId) {
-    if (cache.contains(userId)) {
-      LOGGER.info("# Cache Hit!");
-      return cache.get(userId);
-    }
-    LOGGER.info("# Cache Miss!");
-    UserAccount userAccount = DbManager.readFromDb(userId);
-    cache.set(userId, userAccount);
-    return userAccount;
-  }
-
-  public static void writeThrough(UserAccount userAccount) {
-    if (cache.contains(userAccount.getUserId())) {
-      DbManager.updateDb(userAccount);
-    } else {
-      DbManager.writeToDb(userAccount);
-    }
-    cache.set(userAccount.getUserId(), userAccount);
-  }
-
-  public static void clearCache() {
-    if (cache != null) {
-      cache.clear();
-    }
-  }
-
-  public static void flushCache() {
-    LOGGER.info("# flushCache...");
-    Optional.ofNullable(cache)
-        .map(LruCache::getCacheDataInListForm)
-        .orElse(List.of())
-        .forEach(DbManager::updateDb);
-  }
-
-  /* ... omitted the implementation of other caching strategies ... */
-
-}
-```
-
-`AppManager` helps to bridge the gap in communication between the main class and the application's
-back-end. DB connection is initialized through this class. The chosen caching strategy/policy is
-also initialized here. Before the cache can be used, the size of the cache has to be set. Depending 
-on the chosen caching policy, `AppManager` will call the appropriate function in the `CacheStore` 
-class.
-
-```java
-@Slf4j
-public final class AppManager {
-
-  private static CachingPolicy cachingPolicy;
-
-  private AppManager() {
-  }
-
-  public static void initDb(boolean useMongoDb) { /* ... */ }
-
-  public static void initCachingPolicy(CachingPolicy policy) { /* ... */ }
-
-  public static void initCacheCapacity(int capacity) { /* ... */ }
-
-  public static UserAccount find(String userId) {
-    if (cachingPolicy == CachingPolicy.THROUGH || cachingPolicy == CachingPolicy.AROUND) {
-      return CacheStore.readThrough(userId);
-    } else if (cachingPolicy == CachingPolicy.BEHIND) {
-      return CacheStore.readThroughWithWriteBackPolicy(userId);
-    } else if (cachingPolicy == CachingPolicy.ASIDE) {
-      return findAside(userId);
-    }
-    return null;
-  }
-
-  public static void save(UserAccount userAccount) {
-    if (cachingPolicy == CachingPolicy.THROUGH) {
-      CacheStore.writeThrough(userAccount);
-    } else if (cachingPolicy == CachingPolicy.AROUND) {
-      CacheStore.writeAround(userAccount);
-    } else if (cachingPolicy == CachingPolicy.BEHIND) {
-      CacheStore.writeBehind(userAccount);
-    } else if (cachingPolicy == CachingPolicy.ASIDE) {
-      saveAside(userAccount);
-    }
-  }
-
-  public static String printCacheContent() {
-    return CacheStore.print();
-  }
-
-  /* ... details omitted ... */
-}
-```
-
-Here is what we do in the main class of the application.
-
-```java
-@Slf4j
-public class App {
-
-  public static void main(String[] args) {
-    AppManager.initDb(false);
-    AppManager.initCacheCapacity(3);
-    var app = new App();
-    app.useReadAndWriteThroughStrategy();
-    app.useReadThroughAndWriteAroundStrategy();
-    app.useReadThroughAndWriteBehindStrategy();
-    app.useCacheAsideStategy();
-  }
-
-  public void useReadAndWriteThroughStrategy() {
-    LOGGER.info("# CachingPolicy.THROUGH");
-    AppManager.initCachingPolicy(CachingPolicy.THROUGH);
-    var userAccount1 = new UserAccount("001", "John", "He is a boy.");
-    AppManager.save(userAccount1);
-    LOGGER.info(AppManager.printCacheContent());
-    AppManager.find("001");
-    AppManager.find("001");
-  }
-
-  public void useReadThroughAndWriteAroundStrategy() { /* ... */ }
-
-  public void useReadThroughAndWriteBehindStrategy() { /* ... */ }
-
-  public void useCacheAsideStategy() { /* ... */ }
-}
-```
-
-Finally, here is some of the console output from the program.
-
-```
-12:32:53.845 [main] INFO com.iluwatar.caching.App - # CachingPolicy.THROUGH
-12:32:53.900 [main] INFO com.iluwatar.caching.App - 
---CACHE CONTENT--
-UserAccount(userId=001, userName=John, additionalInfo=He is a boy.)
-----
-```
 
 ## Class diagram
-
 ![alt text](./etc/caching.png "Caching")
 
 ## Applicability
-
 Use the Caching pattern(s) when
 
-* Repetitious acquisition, initialization, and release of the same resource cause unnecessary 
+* Repetitious acquisition, initialization, and release of the same resource causes unnecessary performance overhead.
-  performance overhead.
-
-## Related patterns
-
-* [Proxy](https://java-design-patterns.com/patterns/proxy/)
 
 ## Credits
 
 * [Write-through, write-around, write-back: Cache explained](http://www.computerweekly.com/feature/Write-through-write-around-write-back-Cache-explained)
 * [Read-Through, Write-Through, Write-Behind, and Refresh-Ahead Caching](https://docs.oracle.com/cd/E15357_01/coh.360/e15723/cache_rtwtwbra.htm#COHDG5177)
 * [Cache-Aside pattern](https://docs.microsoft.com/en-us/azure/architecture/patterns/cache-aside)
-* [Java EE 8 High Performance: Master techniques such as memory optimization, caching, concurrency, and multithreading to achieve maximum performance from your enterprise applications](https://www.amazon.com/gp/product/178847306X/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=178847306X&linkId=e948720055599f248cdac47da9125ff4)
-* [Java Performance: In-Depth Advice for Tuning and Programming Java 8, 11, and Beyond](https://www.amazon.com/gp/product/1492056111/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=1492056111&linkId=7e553581559b9ec04221259e52004b08)
-* [Effective Java](https://www.amazon.com/gp/product/B078H61SCH/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=B078H61SCH&linkId=f06607a0b48c76541ef19c5b8b9e7882)
-* [Java Performance: The Definitive Guide: Getting the Most Out of Your Code](https://www.amazon.com/gp/product/1449358454/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=1449358454&linkId=475c18363e350630cc0b39ab681b2687)

caching/src/main/java/com/iluwatar/caching/AppManager.java

@@ -25,7 +25,6 @@ package com.iluwatar.caching;
 
 import java.text.ParseException;
 import java.util.Optional;
-import lombok.extern.slf4j.Slf4j;
 
 /**
  * AppManager helps to bridge the gap in communication between the main class and the application's
@@ -34,7 +33,6 @@ import lombok.extern.slf4j.Slf4j;
  * Depending on the chosen caching policy, AppManager will call the appropriate function in the
  * CacheStore class.
  */
-@Slf4j
 public final class AppManager {
 
   private static CachingPolicy cachingPolicy;
@@ -52,7 +50,7 @@ public final class AppManager {
       try {
         DbManager.connect();
       } catch (ParseException e) {
-        LOGGER.error("Error connecting to MongoDB", e);
+        e.printStackTrace();
       }
     } else {
       DbManager.createVirtualDb();

caching/src/main/java/com/iluwatar/caching/DbManager.java

@@ -30,7 +30,6 @@ import com.mongodb.client.model.UpdateOptions;
 import java.text.ParseException;
 import java.util.HashMap;
 import java.util.Map;
-import lombok.extern.slf4j.Slf4j;
 import org.bson.Document;
 
 /**
@@ -42,7 +41,6 @@ import org.bson.Document;
  * underlying data storage (connect()) or a simple Java data structure to (temporarily) store the
  * data/objects during runtime (createVirtualDB()).</p>
  */
-@Slf4j
 public final class DbManager {
 
   private static MongoClient mongoClient;
@@ -85,7 +83,7 @@ public final class DbManager {
       try {
         connect();
       } catch (ParseException e) {
-        LOGGER.error("Error connecting to MongoDB", e);
+        e.printStackTrace();
       }
     }
     var iterable = db
@@ -112,7 +110,7 @@ public final class DbManager {
       try {
         connect();
       } catch (ParseException e) {
-        LOGGER.error("Error connecting to MongoDB", e);
+        e.printStackTrace();
       }
     }
     db.getCollection(CachingConstants.USER_ACCOUNT).insertOne(
@@ -134,7 +132,7 @@ public final class DbManager {
       try {
         connect();
       } catch (ParseException e) {
-        LOGGER.error("Error connecting to MongoDB", e);
+        e.printStackTrace();
       }
     }
     db.getCollection(CachingConstants.USER_ACCOUNT).updateOne(
@@ -155,7 +153,7 @@ public final class DbManager {
       try {
         connect();
       } catch (ParseException e) {
-        LOGGER.error("Error connecting to MongoDB", e);
+        e.printStackTrace();
       }
     }
     db.getCollection(CachingConstants.USER_ACCOUNT).updateOne(

model-view-viewmodel/README.md

@@ -99,11 +99,11 @@ public class BookViewModel {
 </zk>
 ```
 
-To deploy the example, go to model-view-viewmodel folder and run:
+Note: 
-
+* To deploy this, go to model-view-viewmodel folder and run: 
-* `mvn clean install`
+* mvn clean install
-* `mvn jetty:run -Djetty.http.port=9911`
+* mvn jetty:run -Djetty.http.port=9911
-* Open browser to address: http://localhost:9911/model-view-viewmodel/
+* In browser, http://localhost:9911/model-view-viewmodel/
 
 ## Class diagram