Static and non static class methods question

[silverglade]

Hi, I am reading a book on java , and it looks like this is true.


Static methods can be called without an object of that class being created.

such as Math.sqrt()

and Non static methods must have a Class object created to call the class methods.

such as DecimalFormat fmt = new DecimalFormat ("0.###");

fmt.format(circumference);

the "format" DecimalFormat method is not static so we need the fmt object.


My question is. Why not make all of our methods static so we never need to make an object? please. thank you. Derek

also, my book seems to create objects in 2 ways


way 1: String thisString = "this is a string object";

way 2: Random generator = new Random();

isn't String thisString a variable?


EDIT: I just posted this here. http://www.coderanch.com/t/537914/ja...ethods#2440191

[Iron Lion]

Because that would defeat the purpose of object-oriented programming.

In your example of DecimalFormat, there's a reason that you need to instantiate the class: the instance holds all the formatting information that you give it. You could use a static method to do the same thing, but then if you wanted to use that method to do different things at different points in the program, you'd need to reconfigure it each time.

The syntax for creating strings is a special case defined by the language. If you couldn't specify string literals by using quote marks, you would have to do something like this:

String str = new String('H', 'e', 'l', 'l', 'o', ',', ' ', 'w', 'o', 'r', 'l', 'd');

which would be extremely inconvenient.

isn't String thisString a variable?

thisString is a variable which holds a reference to a String object.

[silverglade]

Awesome Iron Lion, that was great and clear. Now I get it. Thank you!D Derek