Thread: A little help please~~How should i fix it??

(Thanks~~~...This is first time i found this page and post my problem..so....sorry if i did anything wrong.......This code is changing infix to postfix and then calculate out the result)

/** The <code>Stack</code> interface specifies the basic operations
* of a last-in-first-out (LIFO) containers.
*/
public interface Calculation {

public void push(Object object);
/** return the element number in this stack
*/

public double pop();
/**Adds the specified element to the top of this stack.
* @param object the element to be pushed onto this stack.
*/

public Object peek();
/**
* Removes and returns the element at the top of this stack.
* @return the element at the top of this stack.
* @throws IllegalStateException if this stack is empty.
*/

public void resize();
}
(Above is my interface...^^^)

public abstract class ArrayCalculation implements Calculation{
private Object[] stack;
private int top;
private int size;

public void push(){
top++;
stack[top]=top;
}
public double pop(){
Object result = stack[top];
top--;
return (Double) result;
}
public Object top(){
return stack[top];
}
public boolean isFull(){
return(top == size);
}
public boolean isEmpty(){
return(top == -1);
}
public int size(){
return(top + 1);
}

}

import java.util.Scanner;

public class TestArrayCalculation {

public static void main(String[] args)
{
char ch;
ArrayCalculation s;
double operan1, operan2, Result;

System.out.println("The postfix expression is: ");
Scanner scanner = new Scanner(System.in);
String e = scanner.nextLine();

s = new ArrayCalculation(); <<<how should i correct it??
int i = 0;
double trueValue;

while (ch == System.in.read() && ch != '\n') {
ch = e.charAt(i);
i++;
trueValue = ch - 48;
if (Character.isDigit(ch) ){
s.push(trueValue);
}
else {
operan2 = s.pop();
operan1 = s.pop();
switch (ch) {
case '+' : s.push(operan1+operan2);
break;
case '-' : s.push(operan1-operan2);
break;
case '*' : s.push(operan1*operan2);
break;
case '/' : s.push(operan1+operan2);
break;
}
}
}
trueValue = s.pop();
System.out.println(" = " + trueValue);
}
}

s = new ArrayCalculation(); <<<how should i correct it??

What is the compiler message you get on this line? The messages are usually a good place to start - but sometimes they take a little explaining.

[QUOTE=pbrockway2;62745]What is the compiler message you get on this line? The messages are usually a good place to start - but sometimes they take a little explaining.[/QUOTE


(it appear this error message).....
" Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Cannot instantiate the type ArrayCalculation

at TestArrayCalculation.main(TestArrayCalculation.jav a:15) "

Originally Posted by Norm

The javac compiler that I use gives more information. Make sure your IDE is telling you everything that is wrong with the source.

Thanks ! Can you suggest me any better java's software ?

Originally Posted by Norm

I use the javac command included with the JDK

kk...........................thank you very much

Cannot instantiate the type ArrayCalculation

at TestArrayCalculation.main(TestArrayCalculation.jav a:15)

This error seems to arise when you are attempting to run the program, rather than compiling it. Eclipse does give compiler error messages (and underlines things in the code), but I would agree with Norm: use javac to begin with. Apart from anything else you'll get good, extensive, compiler messages that you can cut, copy and post here. The more we have to go on, the better the discussion can be.

"Cannot instantiate the type ArrayCalculation" means that on line 15 you said "new ArrayCalculation()", but the compiler is complaining because ArrayCalculation is an interface and you can only use "new" with a class of some sort. Check your textbook, notes, etc for examples of how an instance of an interface gets created.

OO!!!!!!! ArrayCalculation is point to an interface and "new" use only in calss!!!!@@ Now then i know and i thought every time when i create only whatever then i should put a "new" there.....==....

Thanks for your comment.......
Seem like i need to close this matter and re-coding again~~~

I haven't looked very closely, but I think all you need to do is replace the interface with the appropriate class. (Again you should have notes giving examples).

If there are still problems, post the compiler's message.

My notes show only this and i dont have textbook either.......My lecturer just explain according to the notes but dint say how.....T.T

Sorry - I have just read more closely! (I thought I had remembered from the other day...)

You have declared ArrayCalculation as a class OK, but you made it "abstract". It should not be abstract because you can't use "new" with abstract classes either. Of course you will have to make sure ArrayCalculation implements all of the methods of the Calculation interface including peek() and resize().

OO....ic.....

i just settled and get to run it....haha....thanks for your help....^^