java static keyword

Question

I know the definition of static which is a keyword to refer a variable or method to the class itself. Could this mean if I wrote a method called parseInt() in a class called calculator and another method called parseInt() in a different class called mathProgram, the compiler Eclipse will know which class the method parseInt() is referring to?

score 4 · Answer 1 · edited Apr 13 '22 at 23:20

4

You need to call static methods by referencing the class it is a part of:

MathProgram.parseInt();

Is not the same as

Calculator.parseInt();

So written this way it is clear to the JVM which method you were referring to.

Edit: You can also call static methods using an instance variable but this is in bad form and should be avoided. See this SO answer for more info.

Edit2: Here's a link to the Java Coding Conventions section regarding the use of calling static methods from instance variables. (Thanks to Ray Toal for the link left in the answer to a question posted here)

edited Apr 13 '22 at 23:20

cb4

6,689
7
45
57

answered Oct 25 '11 at 02:02

Jonathan Spooner

7,682
2
34
41

4

True but that's in bad form, yes? – Jonathan Spooner Oct 25 '11 at 02:03
Hopefully, but for completeness, it must be brought up. – Dave Newton Oct 25 '11 at 02:09

score 2 · Answer 2 · answered Oct 25 '11 at 02:01

2

Yes, because static methods and variables must be in a class and to call them outside of that class you need to qualify them.

For example Calculator.parseInt() and OtherClass.parseInt().

Eclipse uses that to tell them apart.

answered Oct 25 '11 at 02:01

cdmckay

31,832
25
83
114

*Java* uses that to tell them apart. – user207421 Oct 25 '11 at 04:58
Eclipse uses Java to tell them apart. – cdmckay Oct 25 '11 at 04:59
And Java uses the class name to tell them apart. Eclipse has nothing to do with it. The program compiles and executes identically whether or not Eclipse is even there, *modulo* Eclipse peculiarities. – user207421 Oct 25 '11 at 07:37
Right, but the question asked how does Eclipse know the difference so I thought I'd keep it simple. – cdmckay Oct 25 '11 at 14:19

score 1 · Answer 3 · edited Apr 13 '22 at 23:21

1

If the method is static, you need to call it using the classname:

Calculator.parseInt();

Otherwise, with an instance:

Calculator c = new Calculator();
c.parseInt();

Either way, its explicit which you want.

edited Apr 13 '22 at 23:21

cb4

6,689
7
45
57

answered Oct 25 '11 at 02:02

ewok

20,148
51
149
254

Although it's generally considered bad practice to use an instance (i.e. `c.parseInt()`) to call a static method. – cdmckay Oct 25 '11 at 04:01
What the answer said is if its static, use the class name. If it is not static, use an instance. – ewok Oct 25 '11 at 12:19

java static keyword

3 Answers3