static initializer vs static block

[Teo Rajkumar]

Hi,

I'm currently studying for my OCA se8 and having been creating lots of simple code examples. I have created this Statics class to play around with the concepts of statics but I encountered this issue.
I'm calling both int values using the class name. Statics.two does not compile but Statics.one does.
Is "static int var=value1" not equivalent to "static{ int var2=value2}" ? If so how do they differ?

public class Statics{
	
 static int one=1;
 static{
 int two=2;
}

 public static void main(String[] args){
   System.out.println(Statics.one);			//Compiles
   System.out.println(Statics.two);			//Doesn't compile	
	
 }
}

[Keith Lynn]

The variable two is a local variable in the static block. It doesn't exist outside the block.

[Puspender Tanwar]

kieth i right
a variable declared in a block (whether it is a instance or static block, or a method block or if, switch etc etc block ) cannot be used outside that block.

Teo Rajkumar wrote: Is "static int var=value1" not equivalent to "static{ int var2=value2}" ? If so how do they differ?

var is a class variable which can be shared among the whole class or outside the class(depending on its access modifier) whereas var2 is a local variable having scope upto static block only.

[Teo Rajkumar]

Focusing on statics, variable scope slipped my mind. Makes perfect sense now. Thanks guys

[Sachin Tripathi]

Hello Rajkumar,
Warm welcome here,
Do you know,here we have an special dedicated section,meant only to help or give guidance for OCA
You can share all your doubts,which you face during the preparation,and be ready to get the answer,in no time

As you mentioned you are practicing static,do read this

[Campbell Ritchie]

Sachin Tripathi wrote:. . . we have an special dedicated section,meant only to help or give guidance for OCA . . .

Good suggestion: shall move thread there.

And welcome again

[Roel De Nijs]

Hi Teo Rajkumar,

First of all, a warm welcome to CodeRanch!

Teo Rajkumar wrote:Is "static int var=value1" not equivalent to "static{ int var2=value2}" ? If so how do they differ?

Definitely not! In this code snippet

public class Statics {
  static int var=1;
  static { int var2=2; }
}

var is a static (or class) variable and var2 is nothing more but a local variable inside the static initializer block. And because var2 is a local variable, you can only access it in the static initializer block itself.

But you could use the static initializer block to initialize static (or class) variables (and then it's equivalent to a static initializer), as illustrated in the following code snippet

public class Statics {
    static int var1 = 1;
    static int var2;
    static {
        var2 = 2;
        int var3 = 3;
        System.out.println("static: var1 = " + var1);
        System.out.println("static: var2 = " + var2);
        System.out.println("static: var3 = " + var3);
    }
    public static void main(String[] args) {
        System.out.println("main: var1 = " + var1);
        System.out.println("main: var2 = " + var2);
        // System.out.println("main: var3 = " + var3); // compiler error
    }
}

Output:
static: var1 = 1
static: var2 = 2
static: var3 = 3
main: var1 = 1
main: var2 = 2

And as a final remark, a static (or class) variable can have the same name as a local variable. Illustrated in this code snippet

class StaticsWithSameName {
    static int var1;
    static {
        var1 = 10;
        int var1 = 100;
        System.out.println("var1 = " + var1);
    }
    public static void main(String[] args) {
        new StaticsWithSameName();
    }
}

And the same applies to instance variables as well

class InstanceVarsWithSameName {
    int var1;
    {
        var1 = 20;
        int var1 = 200;
        System.out.println("var1 = " + var1);
    }
    public static void main(String[] args) {
        new InstanceVarsWithSameName();
    }
}

What do you think the output will be of both code snippets?

Hope it helps!
Kind regards,
Roel