Q:

Add numbers with the word "add"

I am writing to offer an application in Java right now and instead of using the operator "+", the user of the application can literally use the word "add" to add two numbers together. 
I'm quite stuck on how to do this because I can't really use a method in order to complete the function considering I'd have to type "add()" rather than just "add". Unless there is a way to execute a method without the parentheses. Would I have to write a completely new class or is there an easier way to do this?

A:

Just a little explanation on what you could do based on what the user enters:
int x = get it from the user;
int y = get it from the user;
string operation = get it from the user;

Create separate methods for the operations (i.e  add(int x, int y), multiply(int x, int y), etc..)

Then create a method thag gets the values (x, y, string) say.. you can call it calculate(int x, int y, string operation)
Then in the calculuate method have a switch statement:
switch(operation)
{
case "add":
      add(x,y);
      break;
case "multiply":
      multiply(x,y);
      break;
etc...
}

Well, got you something to think about :).

A:

(An expansion on the idea presented by user710502)
You can use reflection.
double a = Double.parseDouble(some user input);
double b = Double.parseDouble(some user input);
String operation = some user input; // i.e. "add", "subtract"
Method operator = Calculations.class.getMethod(operation, double.class, double.class);
// NoSuchMethodException is thrown if method of operation name isn't found
double result = (Double) operator.invoke(null, a, b);

In some sort of calculations class:
public static double add(double a, double b) {
    return a + b;
}

public static double subtract(double a, double b) {
    return a - b;
}

// and so forth

