CODEWITHSUNDEEP
javaerror-handling
kevin gomes
kevin gomes

Reputation: 1815

Regarding `Variable (var-name) might not have been initialized`

import java.io.*;

interface MyIOAction 
{
    void ioAction(Reader rdr) throws IOException;
}

class MyClass
{
    public static void main(String args[]) throws IOException
    {
        Reader rdr1;

        int read = rdr1.read();    //Statement 1

        MyIOAction myIO = (rdr2) -> 
        {
            int ch = rdr2.read();    //Statement 2
        };
    }
}

In the above code, Statement 1 produces the following error

Variable rdr1 might not have been initialized

Whereas Statement 2 compiles successfully.

So, why the same error as in Statement 1 is not produced in the Statement 2?

Upvotes: 0

Views: 34

Answers (2)

AnkeyNigam
AnkeyNigam

Reputation: 2820

Local variables(variables declared inside a method body) rdr1 should be initialized before use . However this rule does not applies to class variables(instance variables).They get their default type value.

As far as rdr2 is concerned , it is Initialised when the method is called. More info about Lambda Exp here 

  public static void main(String args[]) throws IOException
        {
            Reader rdr1; // local variable should be initialized before use

            int read = rdr1.read();    //Statement 1

            MyIOAction myIO = (rdr2) -> // initialized when method is called.Lambda Exp.
            {
                int ch = rdr2.read();    //Statement 2
            };
        }

Upvotes: 0

Ted Hopp
Ted Hopp

Reputation: 234847

In statement 2, rdr2 is in essence a formal argument to a method. It is initialized when the method is invoked. See the Lambda Quick Start or Lambda Expressions tutorials for more information about what's going on with statement 2.

Upvotes: 1

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