> For the complete documentation index, see [llms.txt](https://heunnajo.gitbook.io/java/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://heunnajo.gitbook.io/java/static-method-class-method-and-instance-method.md).

# Static method(Class method) and Instance method

* Summary

1. static method call static method? O
2. static method use instance variable? X
3. static method use instance method? X
4. why? When call static method, object(iv group) might not exist!

Static method = class method

Depend on whether using IV(Instance Variable) or not.

|                     | Instance Method                       | Static Method                   |
| ------------------- | ------------------------------------- | ------------------------------- |
| call                | referencetype\_var\_name.methodname() | class\_name.methodname()        |
| IV(Instance Method) | use IV                                | Not use and non-related with IV |

* Static method example : Math.random(). No need to create object(reference type variable). 

```java
class MyMath2 {
    long a,b;
    
    long add() {//no parameter
        return a+b;//using iv
    }
    static add(long a, long b) {//parameter => local variable
        return a+b;//parameter a and b
    }
}
```

```java
class MyMathTest2 {
    public static void main(String args[]) {
        System.out.println(MyMath.add(200L,100L));//call class method
        
        //instance method
        MyMath2 mm = new MyMath2();
        mm.a = 200L;
        mm.b = 100L;
        System.out.println(mm.add());//call instance method
    }
    
}
```

think about **making static method.**

\=> when **NOT** using iv and im! 

**static variable** : common properties.

CV(Class variable) , CM(Class Method) are available without creating object

**IV, IM are non-available before creating object.**