Write a function that reads a string of digits, possibly preceded by + or -, and converts this string to the integer value it represents.

Write a function that reads a string of digits, possibly preceded by + or -, and converts this string to the integer value it represents. Be sure that your function checksthat the string is well formed, that is, that it represents a valid integer. (Hint: use the functions provided in and ). Also, write a driver programs to test the function.

any help would be highly appreciate.

thanks in advance.

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June 16, 2011 at 4:22 PM

import java.util.*;
public class Driver {

       public static void main(String[] args) {
          Scanner input=new Scanner(System.in);
          int num1=0;    
          int num2=0;   
          char operator=' ';      
          int result=0;       

          System.out.println("Enter expressions such as  17 + 3 or 3.14159 * 4.7");
          System.out.println("Use any of the operators +, -, *, /.");


              System.out.println();
               while (true){
              System.out.print("Enter Expression: ");
              String str=input.nextLine();
              String st[]=str.split(" ");
              if((st[0].matches("((-|\\+)?[0-9]+(\\.[0-9]+)?)+"))&&((st[1].charAt(0)=='+')||(st[1].charAt(0)=='-')||(st[1].charAt(0)=='*')||(st[1].charAt(0)=='/'))&&(st[2].matches("((-|\\+)?[0-9]+(\\.[0-9]+)?)+"))){
                     num1=Integer.parseInt(st[0]);
                     operator = st[1].charAt(0);
                     num2=Integer.parseInt(st[2]);
                  switch (operator) {

                  case '+':
                     result = num1 + num2;
                     break;
                  case '-':
                     result = num1 - num2;
                     break;
                  case '*':
                     result = num1 * num2;
                     break;
                  case '/':
                     result = num1 / num2;
                     break;
                  default:
                    System.out.println("Unknown operator: " + operator);
                      } 
          System.out.println("Result is " + result);
              }
              else{
                  System.out.println("Invalid Expression!");
                  break;
              }
               }


      } 
    }

June 16, 2011 at 5:18 PM

i think here we are not handling Array dynamically, suppose if we given 200+100 , then its trowing array index out of range error,so could you pls help me in this...