inner class within a method

[Stu Higgs]

Hi,

Not sure if this i beginner or intermediate question.

I am currently studying and learing how to work with inner classes.

I was surprised when the follwoing code returned a string representationof the finalLocalVar when I did not call the toString() method directly. If anyone can elaborate on why this happens will appreciate it greatly. Thanks...

CODE:

public class Outer4 {

private int size = 5;

public Outer4(){}

public Object makeTheInner(int localVar){
final int finalLocalVar = 6;
//declare an inner class within a method
class Inner {
public String toString(){
//return " localVar="+localVar;//ERROR: ILLEGAL
return "finalLocalVar = "+finalLocalVar;//LEGAl
}
}//end inner class

return new Inner();//creat instance of Inner
}//end makeTheInner() method

public static void main(String[] args) {
Outer4 outer = new Outer4();
Object obj = outer.makeTheInner(47);
System.out.println("The object is "+obj+"\n");

}

}

[Keith Lynn]

Whenever you use an object reference in an SOP and/or with String concatenation, then an implicit call is made to the toString() of the object that it refers to.
[ July 01, 2006: Message edited by: Keith Lynn ]

[Ilja Preuss]

"stringLiteral" + objectVariable

is translated by the compiler to something like

new StringBuffer().append("stringLiteral").append(objectVariable).toString();

StringBuffer.append(object) delegates to String.valueOf(object), if I remember correctly, which in turn will call object.toString() unless object is null.

[Stu Higgs]

Thanks for your replies.