[Java] Simple Calculator

[Military]

Well, I'm new to Java and it's a bank holiday and I was bored so I made a simple calculator.

/**
 * Personal project
 */
package Mar;

import java.io.*;
import static java.lang.Math.*;
/**
 * @author Re
 *
 */
public class Calculator {

	/**
	 * @param args
	 */
	public static void main(String[] args) throws IOException {
		BufferedReader dataIn = new BufferedReader( new InputStreamReader( System.in));
		//Storage
		int num1 = 0, num2 = 0, result = 0, choice = 0;
		
		double dResult = 0.0;
		// Main Input
		System.out.println("Welcome to Military's calculator");
		System.out.println("Enter 1 for addition, 2 for subtraction");
		System.out.println("Enter 3 for multiplication, 4 for division");
		System.out.println("Enter 5 for square root");
		System.out.println("Enter 0 to exit");
		System.out.println("Enter your choice: ");
		choice = Integer.parseInt(dataIn.readLine());
		
		while(choice != 0){ // Looping calculations
		switch(choice){
		case 1: // Using the addition choice
			System.out.println("Enter 1st number");
			num1 = Integer.parseInt(dataIn.readLine());
			System.out.println("Enter 2nd number");
			num2 = Integer.parseInt(dataIn.readLine());
			result = addNumber(num1, num2);
			System.out.println("The result is "+result+".");
			break;
		case 2: // Using the subtraction choice
			System.out.println("Enter 1st number");
			num1 = Integer.parseInt(dataIn.readLine());
			System.out.println("Enter 2nd number");
			num2 = Integer.parseInt(dataIn.readLine());
			result = subNumber(num1, num2);
			System.out.println("The result is "+result+".");
			break;
		case 3: // Using the multiplication choice
			System.out.println("Enter 1st number");
			num1 = Integer.parseInt(dataIn.readLine());
			System.out.println("Enter 2nd number");
			num2 = Integer.parseInt(dataIn.readLine());
			result = multiNumber(num1, num2);
			System.out.println("The result is "+result+".");
			break;
		case 4: // Using the division choice
			System.out.println("Enter 1st number");
			num1 = Integer.parseInt(dataIn.readLine());
			System.out.println("Enter 2nd number");
			num2 = Integer.parseInt(dataIn.readLine());
			dResult = divNumber(num1, num2);
			System.out.println("The result is "+dResult+".");
			break;
		case 5: // Using the square root choice
			System.out.println("Enter number");
			num1 = Integer.parseInt(dataIn.readLine());
			dResult = squareNumber(num1);
			System.out.println("The result is "+dResult+".");
			break;
		}
		//Loop Input
		System.out.println("Enter your choice: ");
		choice = Integer.parseInt(dataIn.readLine());
	}
		System.out.println("Program was closed!"); // When 0 is pressed
}
	static int addNumber(int num1, int num2){ // Dedicated addition function
		int result = 0;
		result = num1 + num2;
		return result;
		
	}
	
	static int subNumber(int num1,int num2){ // Dedicated subtraction function
		int result = 0;
		result = num1 - num2;
		return result;
		
	}
	
	static int multiNumber(int num1, int num2){ // Dedicated multiplication function
		int result = 0;
		result = num1 * num2;
		return result;
		
	}
	
	static double divNumber(int num1, int num2){ // Dedicated division function
		double result = 0.0;
		result = (num1 / num2);
		return result;
	}
	
	static double squareNumber(int num1){ // Dedicated square function
		double result = 0.0;
		result = sqrt(num1);
		return result;
		
	}
}

I guess I'll add more functions as I get better.

 

[nevS]

Well, I'm new to Java and it's a bank holiday and I was bored so I made a simple calculator.
...
I guess I'll add more functions as I get better.

You could remove duplicated code, example:

while(choice != 0) { // Looping calculations
	System.out.println("Enter 1st number");
	num1 = Integer.parseInt(dataIn.readLine());
	System.out.println("Enter 2nd number");
	num2 = Integer.parseInt(dataIn.readLine());
	switch(choice){
		case 1: // Using the addition choice
			result = addNumber(num1, num2);
			break;
		case 2: // Using the subtraction choice
			result = subNumber(num1, num2);
			break;
		case 3: // Using the multiplication choice
			result = multiNumber(num1, num2);
			break;
		case 4: // Using the division choice
			dResult = divNumber(num1, num2);
			break;
		case 5: // Using the square root choice
			dResult = squareNumber(num1);
			break;
		}
	}

I know the last case is working with just one number, so there is room for improvement, but I hope you get the idea.
Other possible improvements:
- remove the static functions(addNumber etc.), as they have no real benefit.
- replace the magic numbers by enums or constants.
Ofc there is more room for improvement, but since you are new to java this should be enough for now.