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2010-06-01T05:06:43Z

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2010-05-31T17:44:27Z

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== Variable Scope ==

The scope of a variable is the part of the program over which the variable name can be referenced.
(from Ivor Horton"s Beginning Java 2, JDK 5 Edition by Ivor Horton)
You cannot refer to a variable before its declaration.
You can declare variables in several different places:
<OL><LI>In a class body as class fields. Variables declared here are referred to as class-level variables.</LI><LI>As parameters of a method or constructor.</LI><LI>In a method"s body or a constructor"s body.</LI><LI>Within a statement block, such as inside a while or for block.</LI></OL>
Variable scope refers to the accessibility of a variable.
The rule 1 is that variables defined in a block are only accessible from within the block.
The scope of the variable is the block in which it is defined.
For example, consider the following for statement.



<source lang="java">
public class MainClass {
public static void main(String[] args) {
for (int x = 0; x < 5; x++) {
System.out.println(x);
}
}
}</source>



Variables declared as method parameters can be accessed from within the method body.
Class-level variables are accessible from anywhere in the class.
If a method declares a local variable that has the same name as a class-level variable,
the former will "shadow" the latter.
To access the class-level variable from inside the method body, use the this keyword.

== Variable Scope in a block ==



<source lang="java">
public class MainClass {
public static void main(String[] args) {
int outer = 1;
{
int inner = 2;
System.out.println("inner = " + inner);
System.out.println("outer = " + outer);
}
int inner = 3;
System.out.println("inner = " + inner);
System.out.println("outer = " + outer);
}
}</source>



<pre class=codeResult>inner = 2
outer = 1
inner = 3
outer = 1</pre>

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