Simple calculator

[itaiyz97]

Hey guys! I have been trying to write a simple calculator in java yet I didn't get it to work.
Here it is:

 import java.util.*;

 public class FirstClass {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		System.out.println("Please choose the mathematical action you would like to preform.");
		Scanner sc= new Scanner(System.in);
		String x= sc.next();
		
		String w=x;
		if (w=="+") {
			System.out.println("Please type in the numbers you would like to conjugate");
			Scanner sd=new Scanner(System.in);
		    double y= sd.nextDouble();
		    double z= sd.nextDouble();
		    double a= y+z;
		    System.out.println((y+"+"+z+"="+a));
		} else if (w=="-") {
			System.out.println("Please type in the number you would like to substract");
			Scanner se=new Scanner(System.in);
		    double y= se.nextDouble();
		    double z= se.nextDouble();
		    double a= y-z;
		    System.out.println((y+"-"+z+"="+a));
		} else {
			System.err.println("The mathematical function typed was not recognized. Please   type either - or +");
		}
	}
 }

When ever I type + or -, the error message jumps out automatically instead of calculating the doubles.

Thanks for the help!

-IZ

[eRaaaa]

Java: String Comparison

[JosAH]

You can't compare Strings for equality with the == operator, use the equals( ... ) method instead (read the API documentation for the String class).

kind regards,

Jos