Added different object creating strategy

Author: bhuwang

Test1.ser

@@ -10,7 +10,7 @@
 public class AbstractDemo {
     public static void main(String[] args) {
         // abstract class cannot be instantiated
-        
+        // Animal animal = new Animal();
     }
 
 }

src/com/bhuwan/java/basics/abstractclass/AbstractDemo.java

@@ -6,12 +6,15 @@
 /**
  * @author bhuwan
  */
-public abstract class Animal implements Species{
+public abstract class Animal implements Species {
     String name;
 
     public abstract String getSound();
 
     public String getName() {
         return name;
     }
+
+    public Animal() {
+    }
 }

src/com/bhuwan/java/basics/abstractclass/Animal.java

@@ -0,0 +1,40 @@
+/**
+ * 
+ */
+package com.bhuwan.java.basics.oop.constructor;
+
+/**
+ * @author bhuwan
+ *
+ */
+public class ConstructorDemo {
+
+    public ConstructorDemo() {
+        System.out.println("First line should be super");
+        // this(5);
+    }
+
+    public ConstructorDemo(int a) {
+        // First line should be super() or this()
+        System.out.println("Hello");
+        // this("Bhuwan");
+    }
+
+    public ConstructorDemo(String a) {
+        // if we have a recursive constructor call then we will have CTE
+        this(10);
+    }
+
+    public ConstructorDemo(double a) {
+        super();
+        // this(10);
+    }
+
+    public static void main(String[] args) {
+
+    }
+}
+
+abstract class AbstractClass {
+    //
+}

src/com/bhuwan/java/basics/oop/constructor/ConstructorDemo.java

@@ -52,6 +52,8 @@ public static void main(String[] args)
         Runtime runtime = Runtime.getRuntime();
         DateFormat instance2 = DateFormat.getInstance();
         Calendar instance = Calendar.getInstance();
+        Test1 test6 = Test1.getInstance();
+        System.out.println(test6.m1("4. Using factory method."));
 
         // 5. Using Clone method.
         // you must have to override the clone() method.
@@ -68,18 +70,16 @@ public static void main(String[] args)
         ObjectInputStream ois = new ObjectInputStream(fis);
         Test1 test5 = (Test1) ois.readObject();
         System.out.println(test5.m1("6. Using deserialization"));
-
     }
 
 }
 
 class Test1 implements Cloneable, Serializable {
 
-    /**
-     * 
-     */
     private static final long serialVersionUID = 482351728504309257L;
 
+    private static Test1 currentInstance = new Test1();
+
     public Test1() {
     }
 
@@ -95,4 +95,9 @@ public String m1(String message) {
     protected Object clone() throws CloneNotSupportedException {
         return super.clone();
     }
+
+    public static Test1 getInstance() {
+        return currentInstance;
+    }
+
 }

src/com/bhuwan/java/basics/oop/createobject/CreateObjectDemo.java

@@ -5,9 +5,6 @@
 
 import java.io.File;
 import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.Paths;
 
 /**
  * @author bhuwan
@@ -17,31 +14,38 @@ public class CreateNewFile {
     public static void main(String[] args) throws IOException {
         String fileSeparator = System.getProperty("file.separator");
         // absolute file name with path
-        String absoluteFilePath = fileSeparator + "home" + fileSeparator + "bhuwan" + fileSeparator + "filedemo"
-                + fileSeparator + "file.txt";
+        String absoluteFilePath = fileSeparator + "tmp" + fileSeparator + "file.txt";
         File file = new File(absoluteFilePath);
         if (file.createNewFile()) {
             System.out.println(absoluteFilePath + " File Created");
-        }
-        else
+        } else {
             System.out.println("File " + absoluteFilePath + " already exists");
+        }
 
         // file name only
         file = new File("file.txt");
         if (file.createNewFile()) {
             System.out.println("file.txt File Created in Project root directory");
-        }
-        else
+        } else {
             System.out.println("File file.txt already exists in project root directory");
+        }
 
         // relative path
-        String relativePath = "tmp" + fileSeparator + "file.txt";
+        String relativePath = fileSeparator + "tmp" + fileSeparator + "file.txt";
         file = new File(relativePath);
         if (file.createNewFile()) {
             System.out.println(relativePath + " File Created in Project root tmp directory");
-        }
-        else
+        } else {
             System.out.println("File " + relativePath + " already exists in project root tmp directory");
+        }
+
+        // create directory
+        file = new File(fileSeparator + "tmp", "test_directory");
+        if (file.mkdir()) {
+            System.out.println("Directory named " + file + " created successfully.");
+        } else {
+            System.out.println("Directory already exist: " + file);
+        }
     }
 
 }

src/com/bhuwan/java/io/CreateNewFile.java

@@ -0,0 +1,59 @@
+/**
+ * 
+ */
+package com.bhuwan.java.io;
+
+import java.io.File;
+
+/**
+ * @author bhuwan
+ *
+ */
+public class ListFilesInsideHomeDirectory {
+
+    /**
+     * @param args
+     */
+    public static void main(String[] args) {
+        String fileSeparator = System.getProperty("file.separator");
+        File homeDirectory = new File(fileSeparator + "home" + fileSeparator + "bhuwan");
+        System.out.println(homeDirectory.list());
+        String[] list = homeDirectory.list();
+        for (String s : list) {
+            System.out.println(s);
+        }
+        System.out.println("Total Files: " + list.length);
+
+        // display only directories
+        int countDir = 0;
+        for (String s : list) {
+            File f1 = new File(homeDirectory, s);
+            if (f1.isDirectory()) {
+                countDir++;
+                System.out.println(s);
+            }
+        }
+        System.out.println("Total Directories: " + countDir);
+
+        // display only Files
+        int countFiles = 0;
+        for (String s : list) {
+            File f1 = new File(homeDirectory, s);
+            if (f1.isFile()) {
+                countFiles++;
+                System.out.println(s);
+            }
+        }
+        System.out.println("Total Files: " + countFiles);
+
+        System.out.print("Sum of files + Dirs = total files: ");
+        System.out.println((countFiles + countDir) == list.length);
+
+        // display root Files
+        File[] listRoots = File.listRoots();
+        for (File root : listRoots) {
+            System.out.println("Root: " + root);
+        }
+
+    }
+}