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Thread: How to perform operations on arguments with type OBJECT?

  1. #1
    Member hexwind's Avatar
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    Default How to perform operations on arguments with type OBJECT?

    Hello guys
    I'm a Java beginner. I just learned class access controls and whatnot, and I wanted to make a class that I called "Calculus" that has different methods for calculus (addition, multiplication etc). I want the arguments of my methods to handle any type, so I have to use Object (no?). With this, i cannot perform any operation on the arguments. here is an example :
    public class calculus {
     
       public Object add(Object x, Object y)
       {
           return x+y;
     
       }
    }

    I get this error message : Bad Operand types for binary operator '+'

    can anybody help?

    P.S, i don't know if there is already a class in the standard java package that has the methods that i'm writing.
    My website : MediDev


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    Administrator copeg's Avatar
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    Default Re: How to perform operations on arguments with type OBJECT?

    If it is just a mathematical operation, define the method parameters as primitives which can be used directly for mathematical operations. Alternatively, you could pass something like a Number object, using the get* methods to retrieve a primitive value
    See http://download.oracle.com/javase/tu...datatypes.html

  3. #3
    Member hexwind's Avatar
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    Default Re: How to perform operations on arguments with type OBJECT?

    Quote Originally Posted by copeg View Post
    If it is just a mathematical operation, define the method parameters as primitives which can be used directly for mathematical operations. Alternatively, you could pass something like a Number object, using the get* methods to retrieve a primitive value
    See Primitive Data Types (The Java™ Tutorials > Learning the Java Language > Language Basics)
    From what I understand, I have to import the Number library using "import java.lang.Number;" and then 'convert' the arguments of my method to primitive values?
    How would I know if it's an integer that is passed or it's a float? Is there any solution that works regardless of the argument type?
    My website : MediDev

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    Administrator copeg's Avatar
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    Default Re: How to perform operations on arguments with type OBJECT?

    java.lang is a default import so there is not need to explicitly import (give it a try and see). Your methods should define what they accept and the precision they require. If you need floating point math, then define the method as floating point - don't rely on clients (the caller) specifying that behavior - it should be specified in the class you posted.
    public double add(double a, double b){
        return a + b;
    }
    public Number add(Number a, Number b){
        return new Double(a.doubleValue() + b.doubleValue());
    }

  5. #5
    Member hexwind's Avatar
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    Default Re: How to perform operations on arguments with type OBJECT?

    So I should figure out the type of the argument first and change it accordingly and work on it? because, for example, if the client passes it with an integer, i don't want to change it to anything else. i want to perform the operation without changing the arugment's type.
    I'm sorry for my slow understanding, i'm just trying to get a clearer picture :p
    My website : MediDev

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    Super Moderator Norm's Avatar
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    Default Re: How to perform operations on arguments with type OBJECT?

    Look at overloading your add method. Have a method for each type of data. See post #4

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    Administrator copeg's Avatar
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    Default Re: How to perform operations on arguments with type OBJECT?

    A good example of the overloading Norm suggests is demonstrate in Math (Java Platform SE 6)
    For example, the abs/min/max methods have several methods which accept different primitives but accomplish the same task

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