Java programing my first steps

spank · 10-06-2006, 11:39 AM

I'm just begining to program in java using eclipse.

so go easy on me.

One question is how can i use the sqrt function ?
I'm thinking that I have to import something like some libraries.
My only programing experience is in C so if you can make some analogies with that it will sure help.
Thank you!

Some external java resources links will be great.

Nylex · 10-06-2006, 12:01 PM

In Java, the kind of equivalent of "#include <header>" is an import statement. The syntax is as follows:

import package;

There is one package that you don't need to include and that's java.lang, which is included automatically.

In java.lang, you have a class called Math. I haven't done much C, but structs are kind of like classes (at least, C++ classes are like structs in C). The square root function, sqrt(double x) is a static method of that class. What that basically means is you don't need to use that function on a particular instance of that class - it's ok to use the class name to call the function.

Let me show you a quick example of using the square root function:

Code:

// Do we need "import java.lang" here? No, because
// it's included by default.

public class Test
{
  public static void main(String[] args)
  {
    double x = 5;
    double sqrtX = Math.sqrt(5);
  }
}

Does that help at all? I've not touched Java for a while actually and I'm surprised I'm able to remember this stuff!

xhi · 10-06-2006, 12:05 PM

int sqVal = Math.sqrt(val);

you dont have to import math.. but when you need to import something use the organize imports in eclipse.. on the right click menu or keyboard shortcut ctrl+shift+o

hth

edit> im always a little slow i guess..

Dan04 · 10-06-2006, 03:29 PM

Quote:

Originally Posted by Nylex

The square root function, sqrt(double x) is a static method of that class. What that basically means is you don't need to use that function on a particular instance of that class - it's ok to use the class name to call the function.

There's no such thing as java.lang.Math instances. (This is enforced my making the constructor private.) It's just a namespace for static methods, which is a class only because Java requires everything to be in a class.

Nylex · 10-06-2006, 03:32 PM

Ah OK. Haven't done Java for a while, so have forgotten some things. Generally that's true though isn't it, when you have static methods, you don't need an instance of the class. I think that's the same in C++.