Debbie Tom

code
___________________________________________________________________
class for1
{
public static void main(String[] args)
{
int k;
for(int i=0;i<10;i++){
int k;
}
int i;
}
}
_______________________________________________________________________

Gives error "k is already defined in main()"
This means tat for loop doesnt create a scope of it own.

But the declaration of a variable within for loop, has a scope tat ends with for loop.Tatz why wen the declaration is placed before for loop..
it clashes with the scope.

But wen placed after for loop. the scope of the created variable ends with for so it gives no error.

This is my assumption.Any comments on this?

19 years ago

Thanks Tom!

It appears as though a object contains another object but still it does not.It contains only reference.

Can some one shed light upon how the memory will be allocated?
May be tat can make things clear...

19 years ago

ARRAY doubt

A Slightly different explanation

Code:
-----------------------------------------------------------------------
public class Casting21 {
static int[] i1 = {1}, i2 = {3}; //1

static void m1(int[] i1) {//creates a local variable i1.contains value {1)
int[] i3 = i1; //class variable i3 now contains value {1}
i1 = i2;// Variable hiding occurs and local variable i1 is assigned to value of i2-{3}.
i2 = i3; //class variable i2 is assigned i3's value which is {1}
}

public static void main (String[] args) {
m1(i1);
System.out.print(i1[0] + "," + i2[0]);
}
}
-----------------------------------------------------------------------

19 years ago

public class Class01 {
public static void main(String args[]){

char digit='c';
//1
int index=0;
for(;index<10;index++){
switch(digit){
case 'c':
int i1;
default:
int i2;
}
}//FOR
//2
int index=8;
}

}

This gives error.Saying tat variable is already declared in main.

But...

public class Class01 {
public static void main(String args[]){

char digit='c';
//1
;
for(int index=0;index<10;index++){
switch(digit){
case 'c':
int i1;
default:
int i2;
}
}//FOR
//2
int index=8;
}

This dosent give error.
Wat i think is the scope of a varible declared in for getz over with the for loop.

19 years ago

Ritu,

Here the scope of the variable matters.

public class Class01 {
public static void main(String args[]){

char digit='c';
int index; //1

for(int index=0;index<10;index++){
switch(digit){
case 'c':
int i1;
default:
int i2;
}
}//FOR
//2

}
}
Here u can see variables index declared within main method.This is redeclaring a variable.

public class Class01 {
public static void main(String args[]){

char digit='c';
//1

for(int index=0;index<10;index++){
switch(digit){
case 'c':
int i1;
default:
int i2;
}
}//FOR
int index;//2

}
}
In this one variable is declared within main method and other declared as part of class.

Hope this helps!

19 years ago

Hi Ritu,

U get compilation error because,
u are redefining variable-index in the same scope.(scope is determined by the {})

Wen u put tat in //2 the scope of index is over and u are creating another varaible.so u dont get error.

19 years ago

Hi Tom,

My understanding is a object cannot contain another object.
Even though the object a1 appears to contain array(object) arr it contains only a reference to it.The memory for arr is allocated outside of a1.

Each object of the class arrayOb will contain a separate memory of array arr. :

Am i right?

19 years ago

Hi Tom,

Thanks for the reply.Does this statement hold good ?
objects cannot contain objects.

if so, the example does contain a object within object.
Does the memory for the array arr is allocated within the memory of a1?

Wat i understand from ur reply is the object a1 only contains a reference to object arr.Can u explain a bit more on this?

Thanks!

19 years ago

In java, aggregation of objects is only through reference.(Read it in Certification book by Khalid Mughal)
But..

[ September 13, 2005: Message edited by: Michael Ernest ]

19 years ago