Code refactor

Author: javamultiplex

.gitignore

@@ -0,0 +1,3 @@
+.idea
+clean-code.iml
+target

journal.text

@@ -1 +1 @@
-Learn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn Guitar
+Learn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn GuitarLearn to CodeLearn to CodeLearn Guitar

singleton.ser

@@ -1,14 +1,10 @@
 package com.javamultiplex.pattern.creational.singleton;
 
-import java.io.Serializable;
-
 /**
  * @author Rohit Agarwal on 27/08/20 11:59 pm
  * @copyright www.javamultiplex.com
  */
-public class BasicSingleton implements Serializable {
-
-    private static final long serialVersionUID = 1417853001742788063L;
+public class BasicSingleton {
     private static final BasicSingleton INSTANCE = new BasicSingleton();
     private int value;
 
@@ -26,8 +22,4 @@ public int getValue() {
     public void setValue(int value) {
         this.value = value;
     }
-
-    public Object readResolve() {
-        return INSTANCE;
-    }
 }

src/main/java/com/javamultiplex/pattern/creational/singleton/BasicSingleton.java

@@ -0,0 +1,28 @@
+package com.javamultiplex.pattern.creational.singleton;
+
+/**
+ * @author Rohit Agarwal on 27/08/20 11:59 pm
+ * @copyright www.javamultiplex.com
+ */
+public class SingletonV2 {
+    private static final SingletonV2 INSTANCE = new SingletonV2();
+    private int value;
+
+    private SingletonV2() {
+        if (INSTANCE != null) {
+            throw new InstantiationError("Object Creation is not allowed.");
+        }
+    }
+
+    public static SingletonV2 getInstance() {
+        return INSTANCE;
+    }
+
+    public int getValue() {
+        return value;
+    }
+
+    public void setValue(int value) {
+        this.value = value;
+    }
+}

src/main/java/com/javamultiplex/pattern/creational/singleton/SingletonV2.java

@@ -0,0 +1,33 @@
+package com.javamultiplex.pattern.creational.singleton;
+
+/**
+ * @author Rohit Agarwal on 27/08/20 11:59 pm
+ * @copyright www.javamultiplex.com
+ */
+public class SingletonV3 implements Cloneable {
+    private static final SingletonV3 INSTANCE = new SingletonV3();
+    private int value;
+
+    private SingletonV3() {
+        if (INSTANCE != null) {
+            throw new InstantiationError("Object Creation is not allowed.");
+        }
+    }
+
+    public static SingletonV3 getInstance() {
+        return INSTANCE;
+    }
+
+    public int getValue() {
+        return value;
+    }
+
+    public void setValue(int value) {
+        this.value = value;
+    }
+
+    @Override
+    protected Object clone() throws CloneNotSupportedException {
+        throw new CloneNotSupportedException("Object cloning not supported.");
+    }
+}

src/main/java/com/javamultiplex/pattern/creational/singleton/SingletonV3.java

@@ -0,0 +1,40 @@
+package com.javamultiplex.pattern.creational.singleton;
+
+import java.io.Serializable;
+
+/**
+ * @author Rohit Agarwal on 27/08/20 11:59 pm
+ * @copyright www.javamultiplex.com
+ */
+public class SingletonV4 implements Cloneable, Serializable {
+    private static final long serialVersionUID = -6942288218575793523L;
+    private static final SingletonV4 INSTANCE = new SingletonV4();
+    private int value;
+
+    private SingletonV4() {
+        if (INSTANCE != null) {
+            throw new InstantiationError("Object Creation is not allowed.");
+        }
+    }
+
+    public static SingletonV4 getInstance() {
+        return INSTANCE;
+    }
+
+    public int getValue() {
+        return value;
+    }
+
+    public void setValue(int value) {
+        this.value = value;
+    }
+
+    @Override
+    protected Object clone() throws CloneNotSupportedException {
+        throw new CloneNotSupportedException("Object cloning not supported.");
+    }
+
+    public Object readResolve() {
+        return INSTANCE;
+    }
+}

src/main/java/com/javamultiplex/pattern/creational/singleton/SingletonV4.java

@@ -1,9 +1,7 @@
 package com.javamultiplex.pattern.creational.singleton;
 
-import com.javamultiplex.util.SerializationUtil;
 import org.junit.jupiter.api.Test;
 
-import java.io.IOException;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
 import java.util.Arrays;
@@ -18,6 +16,16 @@
  */
 public class BasicSingletonClient {
 
+
+    @Test
+    public void singletonTest() {
+        BasicSingleton instance1 = BasicSingleton.getInstance();
+        BasicSingleton instance2 = BasicSingleton.getInstance();
+        System.out.println(instance1.hashCode());
+        System.out.println(instance2.hashCode());
+        assertSame(instance1, instance2);
+    }
+
     @Test
     public void shouldCreateTwoInstancesUsingReflection() throws IllegalAccessException, InvocationTargetException, InstantiationException {
         BasicSingleton basicSingleton = BasicSingleton.getInstance();
@@ -43,16 +51,4 @@ public void shouldCreateTwoInstancesUsingReflection() throws IllegalAccessExcept
         assertEquals(110, basicSingleton.getValue());
         assertEquals(30, newInstance.getValue());
     }
-
-    @Test
-    public void shouldNotCreateTwoInstancesUsingSerialization() throws IOException, ClassNotFoundException {
-        BasicSingleton basicSingleton = BasicSingleton.getInstance();
-        basicSingleton.setValue(110);
-        SerializationUtil.serialize(basicSingleton, "singleton.ser");
-        BasicSingleton another = (BasicSingleton) SerializationUtil.deserialize("singleton.ser");
-        another.setValue(11);
-        assertSame(basicSingleton, another);
-        assertEquals(11, basicSingleton.getValue());
-        assertEquals(11, another.getValue());
-    }
 }

src/test/java/com/javamultiplex/pattern/creational/singleton/BasicSingletonClient.java

@@ -5,6 +5,9 @@
 
 import java.io.IOException;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+
 /**
  * @author Rohit Agarwal on 29/08/20 11:21 pm
  * @copyright www.javamultiplex.com
@@ -18,6 +21,11 @@ public void shouldNotCreateTwoInstances() throws IOException, ClassNotFoundExcep
         System.out.println(enumBasedSingleton.name());
         SerializationUtil.serialize(enumBasedSingleton, "enum-singleton.ser");
         EnumBasedSingleton another = (EnumBasedSingleton) SerializationUtil.deserialize("enum-singleton.ser");
-        System.out.println(another.getValue());
+        assertEquals(13, another.getValue());
+        assertEquals(13, enumBasedSingleton.getValue());
+        another.setValue(100);
+        assertSame(enumBasedSingleton, another);
+        assertEquals(100, another.getValue());
+        assertEquals(100, enumBasedSingleton.getValue());
     }
 }

src/test/java/com/javamultiplex/pattern/creational/singleton/EnumBasedSingletonClient.java

@@ -0,0 +1,42 @@
+package com.javamultiplex.pattern.creational.singleton;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.util.Arrays;
+import java.util.NoSuchElementException;
+import java.util.Optional;
+
+/**
+ * @author Rohit Agarwal on 28/08/20 12:04 am
+ * @copyright www.javamultiplex.com
+ */
+public class SingletonV2Client {
+
+    @Test
+    public void shouldNotCreateTwoInstancesUsingReflection() throws IllegalAccessException, InvocationTargetException, InstantiationException {
+        SingletonV2 singletonV2 = SingletonV2.getInstance();
+        singletonV2.setValue(110);
+        Class<SingletonV2> singletonV2Class = SingletonV2.class;
+        Constructor<?>[] constructors = singletonV2Class.getDeclaredConstructors();
+        Optional<Constructor<?>> privateConstructor = Arrays.stream(constructors)
+                .filter(constructor -> !constructor.isAccessible())
+                .findAny();
+        Constructor<?> constructor;
+        if (privateConstructor.isPresent()) {
+            constructor = privateConstructor.get();
+            constructor.setAccessible(true);
+        } else {
+            throw new NoSuchElementException("No private constructor found");
+        }
+        InvocationTargetException invocationTargetException = Assertions.assertThrows(InvocationTargetException.class, () ->
+        {
+            SingletonV2 newInstance = (SingletonV2) constructor.newInstance();
+            newInstance.setValue(30);
+        });
+        Assertions.assertEquals(InstantiationError.class, invocationTargetException.getCause().getClass());
+        Assertions.assertEquals("Object Creation is not allowed.", invocationTargetException.getCause().getMessage());
+    }
+}