Blocks and Scopes in Java

Within any class or method, the code between a pair of curly braces is called a block. When you declare a variable within a block, you can not reference that variable outside the block. The portion of a program within which you can reference a variable is the ‘Variables scope’.

Sample Program:
Case: This program defines a variable called ‘x’ inside main method. The scope of the variable x starts with its declaration and must be ends with main method closing curly brace. You can retrieve its value on that scope, but you can’t do it out f scope. So, when you compile program you’ll get “Cannot resolve symbol” error in line 12 which is out of scope of variable ‘x’.

public class VariableScope
{
public static void main(String[] args)
{
//scope of the main method starts
int x = 12;
System.out.println("x is: " + x);
anOtherMethod();
}
//scope of the main method ends

public static void anOtherMethod()
{
//scope of the anOtherMethod starts
System.out.println("x is: " + x);
}
//scope of the anOtherMethod ends
}


This is the output:

Now take a look at this, you may define two variables in different scopes and the variables may overlap.

public class OverlapScope
{
public static void main(String[] args)
{
int x = 55;
System.out.println("main method:- x is: " + x);
overlap();
System.out.println("main method:- x is: " + x);
}

public static void overlap()
{
int x = 66;
System.out.println("overlap method:- x is : " + x);
}
}


The output is:




Even the variable names overlapped, java knows keep in track both variables separately. This is also known as nesting variables.