Initialization of local variables

[Thomas Markl]

Hello,
can you explain the following statement and give examples:
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The Rule is : initialization of a local variable must be done explicitly before the value is used .
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Thanks in advance.
Thomas

[Namrata Shetty]

member variables get default value if u do not assign a value explicitly depending on the type of variable whereas local variables have to be assigned a value explicitly.
for eg.,
1.
public class test
{
int i; //member variable
public static void main(String []args)
{
int j; //local variable
System.out.println(i); //will compile correctly
System.out.println(j); //will give a compile error
}
}
2.
public class test
{
int i; //member variable
public static void main(String []args)
{
int j; //local variable
i=j + 1; //will give a compile error since 'j'is being used without explicitly assigning it a value

j= i +1; no problem since i being a member variable is assigned a default value of 0
}
}
hope this helps!!

[Desai Sandeep]

That's very well explained Namrata
-- Sandeep

[Gurpreet Sachdeva]

Hello Thomas,
I must add one thing to the Namarta's post that local variables have to be assigned a value unconditionally before use.
Gurpreet

[Anonymous]

Originally posted by Gurpreet Sachdeva:
Hello Thomas,
I must add one thing to the Namarta's post that local variables have to be assigned a value [b]unconditionally before use.
Gurpreet[/B]

Excluding the cases where the conditional operator is used.

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Antti Barck
It Solutions Consultant, NSD Oy

[Thomas Paul]

There is actually a reason why instance variables are initialized a method variables aren't. Originally, no variables were going to be given a default value but this opened up several problems. In the case of an instance variable, how would the compiler know if it was initialized prior to use? It could be that it is used in one method but initialized in another method. There could be a requirement to initialize all variables in every constructor (much as we do for final variables) but then what do we do with classes that have only the default constructor? In order to bypass these issues, it was decided to supply default values for instance variables.
But what about method variables? None of these issues exist. The compiler can easily tell if the method variable has been initialized prior to use so there is no reason to supply a default value.
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Tom - SCJP --- Co-Moderator of the Programmer Certification Forums