Write your first program in Java

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We are gonna write our very own first java program. In this article, while we uncover the program we will also learn a new concept called scanner class.

Before we head on to the programming part lets see what scanner class is.

Scanner class

A scanner class in java is nothing but a java util package utility to get the input from the user during runtime.


Scanner input = new Scanner(System.in);


import java.util.Scanner;

public class Testing
    public static void main(String[] args)
        Scanner input = new Scanner(System.in);
        System.out.print("Enter A Number : ");
        double numberOne = input.nextDouble();
        System.out.print("Enter Operator: ");
        String oP = input.next();
        System.out.print("Enter Another Number : ");
        double numberTwo = input.nextDouble();
        if (oP.equals("+"))
        else if (oP.equals("-"))
        else if (oP.equals("*"))
        else if (oP.equals("/"))
        else if (oP.equals("%"))
            System.out.println("Operator Not Found");


Enter A Number : 50
Enter Operator: /
Enter Another Number : 500
  • Using the scanner class we have implemented a simple calculator program.
  • As we know scanner class gets input from users.
  • We are declaring it with object 'input'.
  • Now we are giving a sysout to print some random sentences in this case I have done 'enter a number'.
  • Now, the scanner class has many functions access by control+space there are many datatype functions under the scanner class.
  • It will be in the form on nextDouble, next, etc.
  • What it does is it fetches input from the user with that particular datatype and performs the rest of the action.
  • You can verify them from the return type.
  • Then I have used the if and elseif to do the necessary mathematical operations.
  • If the oP is equal to the user input given as +,-,*,/ etc
  • It will go through the if body and goes in the body of whatever the conditions satisfy based on user input.
  • Thus you can also your mathematical functions like this as well too.