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johny doe
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when i tried to understand a certain code
i got interface called Stack
and a stack class called StackAsArray

1.why are they creating a stack variable called
StackAsArray s = new StackAsArray();

Stack has no meening it just an interface
which inculdes all the method wich we need to create inside of
StackAsArray class.
???

2.when i tried to build this code from scratch
and i written the line
StringTokenizer t = new StringTokenizer(exp);
it sayed that there is no such type
why???

3.in my code i defined a stack and a char like this
StackAsArray st=new StackAsArray();
char ch;

when i tried to pop a member from a stack

ch=(char)st.pop();
it sayd
"cannot convert from object to char"

why ???
i did casting

[ January 01, 2008: Message edited by: johny doe ]
 
Raghavan Muthu
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Originally posted by johny doe:
when i tried to understand a certain code
i got interface called Stack
and a stack class called StackAsArray

1.why are they creating a stack variable called
StackAsArray s = new StackAsArray();



Carefully look at the code. An instance of a class StacksArray has been created and NOT of interface Stack.


Stack has no meening it just an interface which inculdes all the method wich we need to create inside of StackAsArray class.
???


Yes. very true. You don't need to create but define the methods inside the StacksArray class provided if it implements the Stack interface.

Obviously, you don't need an object for an interface and you can't do so. The compiler makes sure the same.
[ January 01, 2008: Message edited by: Raghavan Muthu ]
 
Raghavan Muthu
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Originally posted by johny doe:

2.when i tried to build this code from scratch
and i written the line
StringTokenizer t = new StringTokenizer(exp);
it sayed that there is no such type
why???


Many times you are told Johny Doe.

Kindly make use of separate threads per question. Carefully read this link.

Please stick to the rules. Also spend some time in listening to others who are helping you.
 
Raghavan Muthu
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3.in my code i defined a stack and a char like this
StackAsArray st=new StackAsArray();
char ch;

when i tried to pop a member from a stack

ch=(char)st.pop();
it sayd
"cannot convert from object to char"

why ???
i did casting


Could you please post this in a new thread?
 
johny doe
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what do meen

"its defined as intance"

what does it meen??
for me when i am using a constructor

i am making



but here in this example



Stack is an interface
which meens nothing because i got no code.
and after the word "new" we dont get "Stack"
but "StackAsArray".
i cant understand that.

and how did they use StringTokenizer
because when i tried to wright as they do
it says that there is no such type
[ January 01, 2008: Message edited by: johny doe ]
 
Rob Spoor
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Originally posted by johny doe:
and how did they use StringTokenizer
because when i tried to wright as they do
it says that there is no such type

Have you imported either java.util.StringTokenizer or java.util.*?
 
johny doe
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it worked thanks
 
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