Any class that contains one or more abstract method must also be declared abstract. We can declare an abstract class by using the abstract keyword in front of class keyword at the beginning of the class declaration. An abstract method is a method which declares in super class and defines by the associate subclass. To … Read more
Method overriding is one of the importance concept in Java Programming. What is Method Overriding? In Inheritance hierarchy when a child class defines exact same method that is available in parent class then the method is called overridden method. The process of creating overridden method is called method overriding.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | class Shape { void draw() { System.out.println("Draw Shape"); } } class Triangle extends Shape { void draw() { System.out.println("Draw Triangle Shape"); } } class Rectangle extends Shape { void draw() { System.out.println("Draw Rectangle Shape"); } } class Circle extends Shape { void draw() { System.out.println("Draw Circle Shape"); } } public class MyClass { public static void main(String args[]) { Shape shape = new Shape(); shape.draw(); Triangle triangle = new Triangle(); triangle.draw(); Rectangle rectangle = new Rectangle(); rectangle.draw(); Circle circle = new Circle(); circle.draw(); } } |
Result
1 2 3 4 | Draw Shape Draw Triangle Shape Draw Rectangle Shape Draw Circle Shape |
We have created … Read more
In java programming it is possible to define a class within another class, such classes are known as nested class. There are two types of nested classes:- 1. Non-static inner class … Read more
There are there types of access modifiers in Java. They are: public private and protected. public: A public data can be accessed by outside of the code in which it is defined. private: A private data can not be accessed by outside of the code in which it is defined. The private data can be … Read more
In Java, there are two ways of argument passing. Call by value Call by reference Call by value Whenever we call a method and passes the value of the variable to the called method, it’s called call by value.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | class Demo { void set(int i, int j) { i = i * 2; j = j / 2; } } public class Test { public static void main(String arg[]) { Demo obj = new Demo(); int a = 15, b = 20; System.out.println("Before call a=" + a + " b=" + b); obj.set(a, b); System.out.println("After call a="+a+" "+" b="+b); } } |
Result
1 2 | Before call a=15 b=20 After call a=15 b=20 |
Note: After multiplication and division value of a and b remain unchanged. … Read more
Local Variable Hides Instance Variable In java when the local variable has the same name as an instance variable, the local variable hides the instance variable.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | public class Test { int a=10, b=10;// instance variable a,b public static void main(String agrs[]) { Test t = new Test(); t.display(); } public void display() { int a = 5;//local variable same name as instance variable System.out.println("Value of local variable a=" + a); System.out.println("Value of instance variable a=" + a + " b=" + b); } } |
Result
1 2 3 | Value of local variable a=5 Value of instance variable a=5 b=10 |
In above program we have two instance variable with value a=10 and b=10. in method display there is a local variable a with value 5. Inside … Read more
A Constructor in a special method that is used to initialize the object. Constructor name should be same as class name. Constructors does not have any return type.
1 2 3 4 5 6 | public class Student(){ //constructor Student(){ } } |
While creating object of above class we use
1 | Student student=new Studet() |
Here new is used to create object and after then the constructor Student() is get called it … Read more
Class A class forms the basis for object-oriented programming. It defines the shape and nature of the object. Any concept that we want to implement in oop’s must be encapsulated within a class. A class is a template for an object and an object is an instance for a class. In another words class is … Read more
Command head displays the beginning/top of the file at the terminal. When “head” command is used without any option it will display the beginning/top ten lines of the file. Syntax:
1 | $ head filename [press enter] |
Example: Suppose we have a file Employee.txt as shown below and we want to see the beginning/top of this file by default it will … Read more
Java contains 53 reserved words out of which 50 are keywords. Out of 50, only 48 keywords are used and two keywords const and goto are not in use, and 3 are literals values true, false, and null. These reserved words can not be used as identifiers. Java Keywords The keyword is a reserved word that … Read more
