5.c.Evaluates the Postfix expression

iii) Evaluates the postfix expression.

import java.io.*;

import java.util.*;

class StackDemo

{

static int index,pos;

int T;

float stk[];

StackDemo()

{

stk=new float[10];

T=-1;

index=0;

pos=0;

}

void push(float s)

{

if(T>=19)

{

System.out.println("Stack overflow");

System.exit(0);

}else{

T=T+1;

stk[T]=s;

}

}

float pop()

{

float num;

if(T==-1)

{

System.out.println("Stack is empty");

return(0);

}

else

{

num=stk[T];

T--;

}

return(num);

}

float ExpEval(char sfix[],float data[])

{

int j=0;

float op1,op2,fs;

char ch;

while(sfix[j]!='\0')

{

ch=sfix[j];

if(sfix[j]>='a'||sfix[j]>=

'A'&&sfix[j]<='z'||sfix[j]<='Z')

{

push(data[j]);

}

else

{

op2=pop();

op1=pop();

switch(ch)

{

case '+':push(op1+op2);

break;

case '-':push(op1-op2);

break;

case '*':push(op1*op2);

break;

case '/':push(op1/op2);

break;

case '%':push(op1%op2);

break;

}

}

j++;

}

fs=pop();

return(fs);

}

}

class EvalPostFix

{

public static void main(String args[])

{

String str;

char postfix[]=new char[25];

float number[]=new float[25];

int j=0;

try{

BufferedReader br=new

BufferedReader(new

InputStreamReader(System.in));

System.out.println("Enter a postfix expression:");

str=br.readLine();

str.getChars(0,str.length(),postfix,0);

while(postfix[j]!='\0')

{

if(postfix[j]>='a'||postfix[j]

>='A'&&postfix[j]<='z'||postfix[j]<='Z')

{

System.out.println("enter a number for%c:"+postfix[j]);

number[j]=Integer.parseInt(br.readLine());

}

j++;

}

}

catch(Exception e)

{

System.out.println("Exception \n Read:"+e);

}

StackDemo s1=new StackDemo();

System.out.println("The result is "+s1.ExpEval(postfix,number));

}

}