Java program to read a expression in infix form and convert in postfix form

java program to read a expression in infix form and convert in postfix form

import java.util.*;  
class Stack  
{  
    char a[]=new char[100];  
    int top=-1;  
    void push(char c)  
    {  
        try  
        {  
            a[++top]= c;  
        }  
        catch(StringIndexOutOfBoundsException e)  
        {  
            System.out.println("Stack full, no room to push, size=100");  
            System.exit(0);  
        }  
    }  
    char pop()  
    {  
        return a[top--];  
    }  
    boolean isEmpty()  
    {  
        return (top==-1)?true:false;  
    }  
    char peek()  
    {  
    return a[top];  
    }  
}     
class InfixToPostfix  
{  
    static Stack operators = new Stack(); 
    static int prec(char x)  
    {  
        if (x == '+' || x == '-')  
            return 1;  
        if (x == '*' || x == '/' || x == '%')  
            return 2;  
        return 0;  
    }     
    private static String toPostfix(String infix)  
    {  
        char symbol;  
        String postfix = "";  
        for(int i=0;i<infix.length();++i)  
        {  
            symbol = infix.charAt(i);
     
            if (Character.isLetter(symbol)) 
            {
                postfix = postfix + symbol;  
            }
            else if (symbol=='(')  
            {  
                operators.push(symbol);  
            }  
            else if (symbol==')')   
            {  
                while (operators.peek() != '(')  
                {  
                    postfix = postfix + operators.pop();  
                }  
                operators.pop();        //remove '('  
            }  
            else  
            {  
                while (!operators.isEmpty() && !(operators.peek()=='(') && prec(symbol) <= prec(operators.peek()))  
                    postfix = postfix + operators.pop();  
                operators.push(symbol);  
            }  
        }  
        while (!operators.isEmpty())  
            postfix = postfix + operators.pop();  
        return postfix;  
    }  
    public static void main(String argv[]) 
    {  
        String infix;  
        Scanner sc=new Scanner(System.in);
        System.out.print("\nEnter the infix expression you want to convert: ");  
        infix = sc.nextLine();
        System.out.println("Postfix expression for the given infix expression is:" + toPostfix(infix));  
    } 
}  

Enter the infix expression you want to convert: ((a+b)*(c-d))

Postfix expression for the given infix expression is:ab+cd-*