Is it possible to pass arithmetic operators to a method in java?

Right now I'm going to have to write a method that looks like this:

public String Calculate(String operator, double operand1, double operand2)
{

        if (operator.equals("+"))
        {
            return String.valueOf(operand1 + operand2);
        }
        else if (operator.equals("-"))
        {
            return String.valueOf(operand1 - operand2);
        }
        else if (operator.equals("*"))
        {
            return String.valueOf(operand1 * operand2);
        }
        else
        {
            return "error...";
        }
}

It would be nice if I could write the code more like this:

public String Calculate(String Operator, Double Operand1, Double Operand2)
{
       return String.valueOf(Operand1 Operator Operand2);
}

So Operator would replace the Arithmetic Operators (+, -, *, /...)

Does anyone know if something like this is possible in java?

No, you can't do that in Java. The compiler needs to know what your operator is doing. What you could do instead is an enum:

public enum Operator
{
    ADDITION("+") {
        @Override public double apply(double x1, double x2) {
            return x1 + x2;
        }
    },
    SUBTRACTION("-") {
        @Override public double apply(double x1, double x2) {
            return x1 - x2;
        }
    };
    // You'd include other operators too...

    private final String text;

    private Operator(String text) {
        this.text = text;
    }

    // Yes, enums *can* have abstract methods. This code compiles...
    public abstract double apply(double x1, double x2);

    @Override public String toString() {
        return text;
    }
}

You can then write a method like this:

public String calculate(Operator op, double x1, double x2)
{
    return String.valueOf(op.apply(x1, x2));
}

And call it like this:

String foo = calculate(Operator.ADDITION, 3.5, 2);
// Or just
String bar = String.valueOf(Operator.ADDITION.apply(3.5, 2));

Method arguments in Java must be expressions. An operator by itself is not an expression. This is not possible in Java.

You can, of course, pass objects (maybe enum constants) that represents those operators, and act accordingly, but you can't pass the operators themselves as parameters.

Additional tips

Since you're just starting Java, it's best to ingrain these informations early on to ease your future development.

• Method names starts with lowercase: calculate instead of Calculate
• Variable names starts with lowercase: operator instead of Operator
• Double is a reference type, the box for primitive type double.
  • Effective Java 2nd Edition, Item 49: Prefer primitive types to boxed primitives
• Don't return "error...". Instead, throw new IllegalArgumentException("Invalid operator");

See also

• Java Language Guide/Autoboxing
• Java Lessons/Exceptions
• Coding Conventions/Naming
  • Unfortunate typo in this document: How is this statement making sense? (Sun’s naming convention for Java variables)