Java Static and Instance Methods

In this post, we’ll learn static and instance method in java programming.

/**
  * Author  : DarkL0rd
  * Created : 9 Jan 2023 Monday
  * Define  : Static n Instance Methods
  */


public class StaticDemo {

	//Instance Variable
	
	String instanceMessage = "Instance Variable";
	
	//int count;

	//Static Variable

	static String messages = "Static Variable";


	public static void main(String[] args) {
		
		// Invoke Static to instance variable cant
		//System.out.println(instanceMessage);

		// Invoke Static Variable is OK
		System.out.println(messages);

		//Can invoke to static method from here
		//hello();

		// Greet is not static method
		// Instance Method can't invoke from Static
		//greet();
		
		//Created Objected first and Invoke to InstanceMethod
		StaticDemo demo = new StaticDemo();
		demo.instanceMethod();
	}	

	//Instance Method
	//Instance method's owner is an Object. Not class.
	void instanceMethod() {

		System.out.println("Instance Method");
		
		//Instance Variable
		System.out.println(instanceMessage);

		//Static Variable
		System.out.println(messages);

		//StaticMethod
		hello();

		//InstanceMethod
		greet();
	}

	//Static Method

	static void hello() {
		System.out.println("Hello Static Method");
	}

	//Instance Method

	void greet() {
		System.out.println("Hello Java");
	}
}

Variable Arguments in Java.

public class Varargs {

	//Static Method
	//Only can invoke from included class type

	public static void main(String[] args) {

		// Array
		String [] array = {"A", "B"};

		// Invoking Method
		show("Hello",array);
	}

	static void show(String ... strs) {
		for (String str : strs) {
			System.out.println(str);
		}
	}

	static void show(String string, String ... strs) {
		System.out.println("First " + string);
		for (String str : strs) {
			System.out.println(str);
		}
	}

	// Instance Method
	void greet() {
		System.out.println();
	}
}

Method’s Loading Time for testing.

import java.util.Scanner;

public class LoadingTime {
	public static void main(String[] args) {

		System.out.println("Start Program");

		//Create an obj
		//Scanner obj is waiting to program
		Scanner sc = new Scanner(System.in);
		sc.nextLine();

		LoadDemo demo;
		System.out.println("Declared Class");
		sc.nextLine();

		demo = new LoadDemo();
		System.out.println("Created Object from Class");
		sc.nextLine();

		demo = new LoadDemo();
		System.out.println("Created Object again");
		sc.nextLine();
	}
}

class LoadDemo {

	//Static Block
	//After class declaration, static works
	//Only one time work 
	static {
		System.out.println("Static Block");
	}

	//Instance Block
	//After static works
	{
		System.out.println("Instance Block");
	}

	//Constructor
	//After instance works
	LoadDemo() {
		System.out.println("Constructor");
	}
}