Static Keyword In Java

In this article i have explained the use of 'Static' keyword in different place of java.

like
1.Instance variable
2.In methods
3.In Class
4.In Inner Class -Create Object and call inner static and Non-Static methods.
5.Purpose of Static method and Static Class,static instance variable.
With Sample Program.

S.No	Place of static	Description	When executes	Where Not Include	Sample Code
1	Static block	Nothing but the block of code will be written inside of the static keyword in class .	Called only first time of object creation. First priority will always go to static block even normal block of code present	Inside Methods we can't declare a static block.	Package staticpck.block; public class StaticBlock { { System.out.println("Inside empty block"); } static {System.out.println("Inside static Block");} } package staticpck.block; public class StaticBlockMain { public static void main(String arg[]) {StaticBlock staticBlock=new StaticBlock(); StaticBlock staticBlock1=new StaticBlock(); } } Output: Inside static Block Inside empty block Inside empty block
2	Static Instance Variable	Only one copy for the entire class.(each object reference have only one copy). Even you can access static variable with out creating reference for Object	Only one copy for entire class (Only class name is enough to refer instance variable)	NA(Inside Method local static variable are not possible)	package staticpck.Instvar; public class InstanceVar { static int Instance=1; } package staticpck.Instvar; public class InstanceVarMain { public static void main(String arg[]) { InstanceVar instanceVar=new InstanceVar(); instanceVar.Instance=2; InstanceVar instanceVar2=new InstanceVar(); instanceVar2.Instance=3; System.out.println("instanceVar.Instance="+instanceVar.Instance); }} Output: instanceVar.Instance=3
3	Static @ method	Only one copy for the entire class.(each object reference have only one copy). Even you can access static variable with out creating reference for Object	When a method function is independent of its reference variable in that case we can use Static method.		package staticpck.method; public class Method { public static String getClassDesc() { return "This Class Refers Static Method";} } package staticpck.method; public class MethodImp { public static void main(String[] args) { System.out.println("With Out Obj Ref Call::"+Method.getClassDesc()); System.out.println("With Obj Ref Call::"+new Method().getClassDesc()); }} OutPut: With Out Obj Ref Call::This Class Refers Static Method With Obj Ref Call::This Class Refers Static Method
4	Static @ class	We can't use static for class.	-	Compile time error	-
5	Static in inside method	We can't use static inside method. No use to keep its in Stack memory	-	Compile time error	-
6	Inner class : static @ instance variable	Error msg: The field “sample” cannot be declared static; static fields can only be declared in static or top level types	-	Compile time error	To eliminate error declare inner class as static
7	Inner class : static @ method	Error msg: The method “innermethod” cannot be declared static; static methods can only be declared in a static or top level type	-	Compile time error	To eliminate error declare inner class as static
8	Static @Inner class	If u want to declare static instance/static methods inside the Inner class than Inner class must be declared as Static	All execution are same for outer class		package staticpck.inner; public class InnerSample { static class InnerStatic{ static{ System.out.println("hi i am from inner static block"); } { System.out.println("Hi i am from Inner class block"); } static int instance; static String InnerMethod() { return "I am from Static InnerMethod"; } } class Inner{ //static int instance; String InnerMethod() { return "I am not able to use static due to My hirearchy"; } } } package staticpck.inner; public class InnerSampleImp { public static void main(String arg[]) { System.out.println(InnerSample.InnerStatic.InnerMethod()); InnerSample innerSample=new InnerSample(); InnerSample.Inner inner=innerSample.new Inner(); System.out.println(); } } Output: hi i am from inner static block Innser Static class:I am from Static InnerMethod