CSE2015 Homework March 5, 2018

TextToInteger.java

public class TextToInteger {

  
    public static void main(String[] args) {
        String text = "+1234";
        int number = convertToInteger(text);
        //number++;
        System.out.println(number);
    }

    // Homework:
    // modify this code to make it work for both positive
    // and negative integers
    // write another method that works for floating point
    // numbers
    
    // Reference: study Horner's rule for evaluating polynomials
    // P(x) = 2x^2 - 5x + 20
    private static int convertToInteger(String text) {
        int number = 0;
        
        // case: negative number
        if(text.charAt(0)=='-'){
            for (int i = 1; i < text.length(); i++){
            char ch = text.charAt(i);
            int digit = ch - '0';
            number = number * 10 + digit; 
            }
            number *= -1; 
        }
        
        // case: positive number with "+" sign given
        else if(text.charAt(0)=='+'){   
            for (int i = 1; i < text.length(); i++){
            char ch = text.charAt(i);
            int digit = ch - '0';
            number = number * 10 + digit;
             
            }
        }
            
        
      // case: positive number
        else{
        
            for (int i = 0; i < text.length(); i++) {
            char ch = text.charAt(i);
            int digit = ch - '0';
            number = number * 10 + digit;
        }    
        }
        
        return number;
    }
    
    
}