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This Java program simply creates an option to chose the Operators just like any calculator. A switch statement is used for creating an option in programming that will make case for a different option and operate according to the option that the user provides. It will also take two operands (numbers) at the beginning.

If you do not know about the Switch Case statement or Data Types in java, click the link below to learn about them as this program uses one.

• Switch Case Statement in Java
• Data-types in Java

Java Program to make a Calculator using a Switch Statement

 //Making Calculator using a switch in Java
  
 import java.util.Scanner;

 public class CalculatorJava
 {
   public static void main(String[] args)
   {
     double result;
     char operator;
     Scanner reader = new Scanner(System.in);

     System.out.print("Enter first numbers: ");
     double num1 = reader.nextDouble();

     System.out.print("Enter second numbers: ");
     double num2 = reader.nextDouble();

     System.out.print("Choose an operator(+, -, *, /): ");
     operator=reader.next().charAt(0);

     //switch case 
     switch (operator)
     {
       case '+':
         result = num1 + num2;
         break;

       case '-':
         result = num1 - num2;
         break;

       case '*':
         result = num1 * num2;
         break;

       case '/':
         result = num1 / num2;
         break;

       default:
         System.out.printf("Error! operator is not correct");
         return;
     }

     //Displaying result
     System.out.printf("%.1f %c %.1f = %.1f", num1, operator, num2, result);
   }
 }

Output:

Enter first numbers: 5
Enter second numbers: 3
Choose an operator (+, -, *, /): -
5.0 - 3.0 = 2.0

Here, you will learn how to calculate the Simple Interest in Java using the Formula ((p * r * t) / 100)) where,

• p = Principal
• r = Rate of Interest
• t = Time Period

The program takes the user input for Principal, Rate, and Time, calculates the result, and displays the result on the screen.

If you do not know about the operators or Data Types in java, click the link below to learn about operators as this program is using one.

• Java Operator
• Data-types in Java

Java Program to Calculate the Simple Interest

 //Simple Interest in Java
  
 import java.util.Scanner;

 public class SimpleInterestJava
 {
    public static void main(String args[]) 
    {
     float p, r, t, SI;
    
     Scanner scan = new Scanner(System.in);
    
     System.out.print("Enter the value for Principal: ");
     p = scan.nextFloat();
    
     System.out.print("Enter the value for Rate of interest: ");
     r = scan.nextFloat();
    
     System.out.print("Enter the value for Time period: ");
     t = scan.nextFloat();
     scan.close();
    
     SI = (p * r * t) / 100;
     System.out.print("Simple Interest is: " +SI);
    }
 }

Output:

Enter the value for Principal: 1000
Enter the value for Rate of interest: 5
Enter the value for Time period: 2
Simple Interest is: 100.0

The above source code to calculate the Simple Interest in Java is compiled and ran successfully on a windows system. Browse through Java Program to learn more.

Here, you will learn how to calculate the Area of a Triangle using the Formula [(Base* Height)/2]. The program takes the user input for the Base and Height of a triangle, calculates the result, and displays the result on the screen.

If you do not know about the operators in java, click the link below to learn about operators as this program is using one.

• Java Operator

Java Program to Calculate the Area of a Triangle

 //Area of a traingle

 import java.util.Scanner;

 public class AreaOfTriangle 
 {
    public static void main(String args[]) 
    {   
        Scanner sc = new Scanner(System.in);

        System.out.println("Enter the base of the Triangle:");
        float base = sc.nextFloat();

        System.out.println("Enter the height of the Triangle:");
        float height = sc.nextFloat();

        //Area = (base*height)/2
        float area = (base* height)/2;
        System.out.println("Area of the Triangle is: " + area);      
    }
 }

Output:

Enter the base of the Triangle:
8
Enter the height of the Triangle:
10
Area of the Triangle is: 40.0

Here, you will learn how to calculate the Area of a Square using the Formula (Side* Side). The Program takes the user input for Side, calculates the result, and displays the result on the screen.

If you do not know about the operators in java, click the link below to learn about operators as this program is using one.

• Java Operator

Java Program to Calculate the Area of a Square

 //Area of a square
  
 import java.util.Scanner;
 
 public class AreaofSquare 
 {
    public static void main (String[] args)
    {
        Scanner scanner = new Scanner(System.in);
        
        System.out.print("Enter Side of Square: ");
        float side = scanner.nextInt();
        
        //Area = side*side
        float area = side*side; 
        System.out.println("Area of Square is: "+area);
    }
 }

Output:

Enter Side of Square: 4
Area of Square is: 16.0

Here, you will learn how to calculate the Area of a Rectangle using the Formula (Length * Breadth). The program takes the user input for length and breadth, calculates the result, and displays the result on the screen.

If you do not know about the operators in java, click the link below to learn about operators as this program is using one.

• Java Operator

Java Program to Calculate the Area of a Rectangle

import java.util.Scanner;

public class AreaRectangle
{
  public static void main(String[] args)
  {
    int len, br, result;
    Scanner sc = new Scanner(System.in);

    //Taking Inputs from Users
    System.out.print("Enter the length: ");
    len = sc.nextInt();
    System.out.print("Enter the breadth: ");
    br = sc.nextInt();

    sc.close();
    result = len * br;
    System.out.println("Area of a rectangle: " + result);
  }
}

Output:

Enter the length: 2
Enter the breadth: 5
Area of a rectangle: 10

The java program below uses Math.PI property of java that returns approx 3.14159. The program takes the user input for the value of radius and calculates using the formula of Area and Circumference of a circle and displays the output accordingly.

Java Program to Calculate the Area and Circumference of a Circle

 //Area and circumference of circle

 import java.util.Scanner;

 public class AreaCircumCircle
 {
    
   public static void main(String args[])
   {
     Scanner sc = new Scanner(System.in);
     System.out.print("Enter the radius: ");
    
     double radius = sc.nextDouble();
    
     //Area = PI*radius*radius
     double area = Math.PI * (radius * radius);
     System.out.println("The area of a circle is: " + area);
    
     //Circumference = 2*PI*radius
     double circumference= Math.PI * 2*radius;
     System.out.println( "The circumference of a circle is:"+circumference) ;
   }
 }

Output:

Enter the radius: 7
The area of a circle is: 153.93804002589985
The circumference of a circle is:43.982297150257104

The example below shows how to take two integers as an input from the user using Scanner and multiply them and display the final result on the screen in Java.

Before that, if you do not about the operators in Java, click the link below and learn about it.

• Operators in Java

Java program to find the Product of Two Numbers:

//product of two numbers

 import java.util.Scanner;

 public class ProductOfTwoNumbers 
 {
    public static void main(String[] args) 
    {
        Scanner scan = new Scanner(System.in);
        System.out.print("Enter first number: ");

        // reads the input number
        int num1 = scan.nextInt();
        
        System.out.print("Enter second number: ");
        int num2 = scan.nextInt();

        // Closing Scanner after the use
        scan.close();
        
        // product of two numbers
        int product = num1*num2;
        
        // Displaying the result
        System.out.println("Product of two numbers is: "+product);
    }
 }

Output:

 Enter first number: 7
 Enter second number: 7
 Product of two numbers is: 49

This Java program adds two integers given in the program and displays the result on the screen.

To understand the topic, you need to have a basic understanding of two basic topics in Java.

• Java Operator
• Java Input/Output

Java Program for the Sum of two numbers

//Addition of two numbers
 
 public class AddTwoNumbers 
 {

   public static void main(String[] args) 
   {
        
     int num1 = 20, num2 = 30, sum;
     sum = num1 + num2; //adding two numbers

     //Display result
     System.out.println("Sum of num1 and num2: "+sum);
   }
}

Output:

Sum of num1 and num2: 50

Java Program for the Sum of two numbers using Scanner

The Scanner class is used to get the inputs from the users in Java programming. We need to import a scanner class at the beginning.

import java.util.Scanner;
public class AddTwoNumbers
{
  public static void main(String[] args)
  {
    int num1, num2, sum;
    Scanner sc = new Scanner(System.in);

    //Taking Inputs from Users
    System.out.println("Enter First Number: ");
    num1 = sc.nextInt();
    System.out.println("Enter Second Number: ");
    num2 = sc.nextInt();

    sc.close();
    sum = num1 + num2;
    System.out.println("Sum of these numbers: " + sum);
  }
}

Output:

Enter First Number:
10
Enter Second Number:
5
Sum of these numbers: 15