Stack that implements try and catch problem

Question

Hi guys, i'm pretty new to java (and programming all together) , have a difficulties with this calculator i'm working on.
I've got a stack which holds for instance 5 + 6 * 2
which equals 17. What i have is:
Stack<String> expression = new Stack<String>(
while(expression.size() >= 2){
String X = new String();
String Y = new String();
X = expression.pop();
System.out.println("popin stack"+X); //debuggin purposes
try {double x = Double.parseDouble(X);  
               if (X.equals('+')) {
                   Y = expression.pop();
                   double y = Double.parseDouble(Y);
                   String result = Operation.PLUS.eval(x,y);
                   System.out.println(result);
                   expression.push(result);
else if (X.equals('-')) {
Y = expression.pop();
double y = Double.parseDouble(Y);
String result = Operation.MINUS.eval(x,y);
System.out.println(result);
expression.push(result);
else if (X.equals('/')) {
Y = expression.pop();
double y = Double.parseDouble(Y);
String result = Operation.DIVIDE.eval(x,y);
System.out.println(result);
expression.push(result);
else {
Y = expression.pop();
double y = Double.parseDouble(Y);
String result = Operation.TIMES.eval(x,y);
System.out.println(result);
expression.push(result);
catch () { }
My idea behinde this was i'd used the try statement
to prevent the element being converted to a double if it isn't a String which this can be done to i.e any integer. I'm not sure if i've gone about this right. And have not idea of what i'm suppose to be catchin i.e the throwable?. Any input/direction would be great, thanks.

Answer 1

Hi guys, i'm pretty new to java (and programming all together) , have a difficulties with this calculator i'm working on.
I've got a stack which holds for instance 5 + 6 * 2
which equals 17. What i have is:
Stack<String> expression = new Stack<String>(
while(expression.size() >= 2){
     String X = new String();
     String Y = new String();
     X = expression.pop();
     System.out.println("popin stack"+X); //debuggin purposes
     try {double x = Double.parseDouble(X);
     if (X.equals('+')) {
           Y = expression.pop();
           double y = Double.parseDouble(Y);
           String result = Operation.PLUS.eval(x,y);
           System.out.println(result);
           expression.push(result);
      else if (X.equals('-')) {
           Y = expression.pop();
           double y = Double.parseDouble(Y);
           String result = Operation.MINUS.eval(x,y);
           System.out.println(result);
           expression.push(result);
     else if (X.equals('/')) {
           Y = expression.pop();
           double y = Double.parseDouble(Y);
           String result = Operation.DIVIDE.eval(x,y);
           System.out.println(result);
           expression.push(result);
     else {
           Y = expression.pop();
           double y = Double.parseDouble(Y);
           String result = Operation.TIMES.eval(x,y);
           System.out.println(result);
           expression.push(result);
     catch () { }
} My idea behinde this was i'd used the try statement
to prevent the element being converted to a double if it isn't a String which this can be done to i.e any integer. I'm not sure if i've gone about this right. And have not idea of what i'm suppose to be catchin i.e the throwable?. Any input/direction would be great, thanks.
Edited by: javaUser on Dec 30, 2007 5:59 PM