Hello World

code: com.java.basics.App01

public class App01 {

    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

compile: javac App01.java
run: java App01
output: Hello World

Blocks {}

Java has 2 types of blocks.

1. static blocks (executed without object creation during class load time only)
2. non-static(instance) blocks.(executed every time an object created)

Static Blocks

code: com.java.basics.App02

• A block {} prefixed with the keyword static.
• Always executes whenever the class is loaded.
• Execution of static block does not dependent on the object creation.
• Static blocks execute in order of declaration.

public class App02 {
    static {
        System.out.println("static block 1");
    }
    static {
        System.out.println("static block 2");
    }
    public static void main(String[] args) {

    }
}

• When we run above program the class gets loaded and as a result the static blocks executed in order.

output:

static block 1
static block 2

Static Block and Main method

code: com.java.basics.App03

• Static blocks always execute before the execution of main method.
• The signature of main method is `public static void main(String[] args)

public class App03 {
    static {
        System.out.println("static block 1");
    }
    static {
        System.out.println("static block 2");
    }
    public static void main(String[] args) {
        System.out.println("from main method");
    }
}

output:

static block 1
static block 2
from main method

Non-Static Blocks

Static and Non-Static Blocks

Variables & Primitive Data Types

Static Variables

Non-Static Variables

Local Variables

Constants or Final Variable

Static Methods

Non-Static Methods

Methods with parameters

Methods with return type

Static Blocks & Static Variables

Static Blocks & Static Methods

Non-Static Blocks & Non-Static Methods

Non-Static Blocks & Non-Static Variables

Non-Static Blocks & Static Methods

Non-Static Blocks & Static Variables

Method Calling Another Method

Reference Type Variable

Accessing Methods of Another Class

Constructor

Parameterized Constructor

Interface implements

Abstract Class extends

Extending Concrete class

Strategy Design

Template Design