In Java programming, when a program begins the first thread that starts running is called main thread. Other threads(child thread) can be spawned from this main thread. When program terminates, the main thread must be the last thread in the program to end. When the main thread stops, the program stops running. Main thread is … Read more
In java exception handling, any code that we want to must be execute put inside the finally block. After the execution of try and catch block, finally block executes. try block must be used with either catch or finally, or with both. Normally when exception occurs then further programs never executes. But either exception occurs … Read more
In Java programming, an interface is a collection of method declaration and constant that one or more class can use. It is syntactically similar to the class but the main difference between class and interface is that class contain method declaration with method body and interface method declares without any body. Syntax of interface:
1 2 3 4 5 6 7 8 9 10 11 | access specifier interface InterfaceName { type var1 = value; type var2 = value; ..... .... type method1(parameter list); type method2(parameter list); } |
Final is using for three purpose: final is used to prevent method overriding final is used to prevent inherit a class final is used to make a variable constant final is used to prevent overriding: A method declared as final can’t be overridden.
1 2 3 4 5 6 7 8 9 10 11 | class A { final void show() { } } class B extends A { void show() { //error, can’t override } } |
Because show() declared as final, it can’t be overridden in B. If … Read more
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
