Notes

package csdappliccation;
import java.util.*;
public class EXF2_38
{
public static class Stack<T>
{
private int top = 0;
private final static int stackMax = 25;
// highest index of stk array
private Object[] stk = new Object[stackMax+1];
public Stack()
{
}
// other methods
public boolean isEmpty()
{
if(top==0)
return true;
else
return false;
}
public void push(T el)
{
if (top == stackMax) // is stack full ?
System.out.println("Stack Push Overflow Error");
else
{
top++;
stk[top]=el;
}
}
public T pop()
{
if(isEmpty())
{
System.out.println("Stack Pop Underflow Error");
return null;
}
else
{
top= top-1;
return (T) stk[top+1];
}
}
public void clear()
{
top=0;
}
public static boolean isOperator(String x)
{
char c=x.charAt(0);
return(c=='+' || c=='-' || c=='/' || c=='*'|| c=='^');
}

public static double evaluate(double x, String o, double y)
{
char c=o.charAt(0);
double result=0;
switch(c)
{
case '+' : result=x+y; break;
case '-' : result=x-y; break;
case '*' : result=x*y; break;
case '/' : result=x/y; break;
case '^' : result=Math.pow(x,y); break;
default : break;
}
return result;
}

public static double evaluatePostfix(String e)
{
Stack<Double> s = new Stack<Double>();
String[] x=toCharArray(e);
double a=0,b=0;


for (int i = 0; i < x.length; i++)
{
if(!isOperator(x[i]))
{
s.push(Double.parseDouble(x[i]));
}
else
{
b=s.pop();
a=s.pop();
Print(a,b,x[i]);
s.push(evaluate(a,x[i],b));
}

}
return s.pop();
}

public static void Print(double b, double a, String o){
System.out.printf("%.0ft%.0fn",b , a);
evaluate(a,o,b);
}

public static String[] toCharArray(String inp){
String[] s = inp.split(" ");
return s;
}
}
public static void main(String[] args)
{
char again;
do
{
Scanner input= new Scanner(System.in);
System.out.println("Input PostFix Expression: ");
String w= input.nextLine();
double q = Stack.evaluatePostfix(w);
System.out.printf("%.0fn",q);
System.out.printf("The answer is %.0fn",q);
System.out.print("Try Again? [y/anykey]");
again= input.next().charAt(0);
}while(again=='y' || again=='Y');
}
}