oop 2

kunal-kushwaha · kunal-kushwaha · commit a267a9a4d57f · 2021-11-05T19:44:26.000+05:30
diff --git a/lectures/17-oop/code/.idea/uiDesigner.xml b/lectures/17-oop/code/.idea/uiDesigner.xml
diff --git a/lectures/17-oop/code/src/com/kunal/introduction/Main.java b/lectures/17-oop/code/src/com/kunal/introduction/Main.java
@@ -1,6 +1,7 @@
 package com.kunal.introduction;
 
 import java.sql.Struct;
+import java.util.ArrayList;
 import java.util.Arrays;
 
 public class Main {
diff --git a/lectures/17-oop/code/src/com/kunal/introduction/WrapperExample.java b/lectures/17-oop/code/src/com/kunal/introduction/WrapperExample.java
@@ -23,11 +23,13 @@ public static void main(String[] args) {
         // when a non primitive is final, you cannot reassign it.
 //        kunal = new A("new object");
 
-        A obj;
+        A obj = new A("Rnadvsjhv");
 
-        for (int i = 0; i < 1000000000; i++) {
-            obj = new A("Random name");
-        }
+        System.out.println(obj);
+
+//        for (int i = 0; i < 1000000000; i++) {
+//            obj = new A("Random name");
+//        }
 
     }
 
diff --git a/lectures/17-oop/code/src/com/kunal/packages/a/Greeting.java b/lectures/17-oop/code/src/com/kunal/packages/a/Greeting.java
@@ -0,0 +1,10 @@
+package com.kunal.packages.a;
+
+import static com.kunal.packages.b.Message.message;
+
+public class Greeting {
+    public static void main(String[] args) {
+        System.out.println("Hello world");
+        message();
+    }
+}
diff --git a/lectures/17-oop/code/src/com/kunal/packages/b/Greeting.java b/lectures/17-oop/code/src/com/kunal/packages/b/Greeting.java
@@ -0,0 +1,7 @@
+package com.kunal.packages.b;
+
+public class Greeting {
+    public static void main(String[] args) {
+        System.out.println(" I am awesome");
+    }
+}
diff --git a/lectures/17-oop/code/src/com/kunal/packages/b/Message.java b/lectures/17-oop/code/src/com/kunal/packages/b/Message.java
@@ -0,0 +1,11 @@
+package com.kunal.packages.b;
+
+public class Message {
+    public static void main(String[] args) {
+
+    }
+
+    public static void message() {
+        System.out.println("This course is awesome");
+    }
+}
diff --git a/lectures/17-oop/code/src/com/kunal/singleton/Main.java b/lectures/17-oop/code/src/com/kunal/singleton/Main.java
@@ -0,0 +1,13 @@
+package com.kunal.singleton;
+
+public class Main {
+    public static void main(String[] args) {
+        Singleton obj1 = Singleton.getInstance();
+
+        Singleton obj2 = Singleton.getInstance();
+
+        Singleton obj3 = Singleton.getInstance();
+
+        // all 3 ref variables are pointing to just one object
+    }
+}
diff --git a/lectures/17-oop/code/src/com/kunal/singleton/Singleton.java b/lectures/17-oop/code/src/com/kunal/singleton/Singleton.java
@@ -0,0 +1,19 @@
+package com.kunal.singleton;
+
+public class Singleton {
+    private Singleton () {
+
+    }
+
+    private static Singleton instance;
+
+    public static Singleton getInstance() {
+        // check whether 1 obj only is created or not
+        if (instance == null) {
+            instance = new Singleton();
+        }
+
+        return instance;
+    }
+
+}
diff --git a/lectures/17-oop/code/src/com/kunal/staticExample/Human.java b/lectures/17-oop/code/src/com/kunal/staticExample/Human.java
@@ -0,0 +1,22 @@
+package com.kunal.staticExample;
+
+public class Human {
+    int age;
+    String name;
+    int salary;
+    boolean married;
+    static long population;
+
+    static void message() {
+        System.out.println("Hello world");
+//        System.out.println(this.age); // cant use this over here
+    }
+
+    public Human(int age, String name, int salary, boolean married) {
+        this.age = age;
+        this.name = name;
+        this.salary = salary;
+        this.married = married;
+        Human.population += 1;
+    }
+}
diff --git a/lectures/17-oop/code/src/com/kunal/staticExample/InnerClasses.java b/lectures/17-oop/code/src/com/kunal/staticExample/InnerClasses.java
@@ -0,0 +1,32 @@
+package com.kunal.staticExample;
+
+import java.util.Arrays;
+
+public class InnerClasses {
+
+    static class Test {
+        String name;
+        public Test(String name) {
+            this.name = name;
+        }
+
+        @Override
+        public String toString() {
+            return name;
+        }
+    }
+
+    public static void main(String[] args) {
+        Test a = new Test("Kunal");
+        Test b = new Test("Rahul");
+
+        System.out.println(a);
+
+//        System.out.println(a.name);
+//        System.out.println(b.name);
+    }
+}
+
+//static class A {
+//
+//}
diff --git a/lectures/17-oop/code/src/com/kunal/staticExample/Main.java b/lectures/17-oop/code/src/com/kunal/staticExample/Main.java
@@ -0,0 +1,40 @@
+package com.kunal.staticExample;
+
+public class Main {
+    public static void main(String[] args) {
+//        Human kunal = new Human(22, "Kunal", 10000, false);
+//        Human rahul = new Human(34, "Rahul", 15000, true);
+//        Human arpit = new Human(34, "arpit", 15000, true);
+//
+//        System.out.println(Human.population);
+//        System.out.println(Human.population);
+//        System.out.println(Human.population);
+
+        Main funn = new Main();
+        funn.fun2();
+
+    }
+
+    // this is not dependent on objects
+    static void fun() {
+//        greeting(); // you cant use this because it requires an instance
+        // but the function you are using it in does not depend on instances
+
+        // you cannot access non static stuff without referencing their instances in
+        // a static context
+
+        // hence, here I am referencing it
+        Main obj = new Main();
+        obj.greeting();
+    }
+
+    void fun2() {
+        greeting();
+    }
+
+    // we know that something which is not static, belongs to an object
+    void greeting() {
+//        fun();
+        System.out.println("Hello world");
+    }
+}
diff --git a/lectures/17-oop/code/src/com/kunal/staticExample/StaticBlock.java b/lectures/17-oop/code/src/com/kunal/staticExample/StaticBlock.java
@@ -0,0 +1,26 @@
+package com.kunal.staticExample;
+
+// this is a demo to show initialisation of static variables
+public class StaticBlock {
+    static int a = 4;
+    static int b;
+
+    // will only run once, when the first obj is create i.e. when the class is loaded for the first time
+    static {
+        System.out.println("I am in static block");
+        b = a * 5;
+    }
+
+    public static void main(String[] args) {
+        StaticBlock obj = new StaticBlock();
+        System.out.println(StaticBlock.a + " " + StaticBlock.b);
+
+        StaticBlock.b += 3;
+
+        System.out.println(StaticBlock.a + " " + StaticBlock.b);
+
+        StaticBlock obj2 = new StaticBlock();
+        System.out.println(StaticBlock.a + " " + StaticBlock.b);
+    }
+
+}
diff --git a/lectures/17-oop/notes/OOP-1.pdf b/lectures/17-oop/notes/OOP-1.pdf
diff --git a/lectures/17-oop/notes/classes.txt b/lectures/17-oop/notes/classes.txt
diff --git a/lectures/17-oop/notes/constructors_this_finalize.txt b/lectures/17-oop/notes/constructors_this_finalize.txt
