I wrote this code to convert roman to integer but this code is throwing exception.

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I wrote this code to convert Roman to Integer But this code is throwing  index out of bound exception.

What I have tried:

<pre>package practice_projects;

import java.util.*;

public class roman {

	public static void main(String[] args) {
		
		int result = 0;
			Scanner scan = new Scanner(System.in);
        
			
        
        HashMap<string,integer>roman = new HashMap<string,integer>();
        
        roman.put("I",1);
         roman.put("V",5);
         roman.put("X",10);
         roman.put("L",50);
         roman.put("C",100);
         roman.put("D",500);
         roman.put("M",1000);
        
         String input = scan.next();
         String input_final = input.toUpperCase();
         	
      
         
         for(int i=0;i<=input_final.length();i++) {
              
        	 if(input_final.charAt(i)>input_final.charAt(i-1)) {
        		 		result += roman.get(input_final.charAt(i-1))-roman.get(input_final.charAt(i));
        	 }else {
        		 result += roman.get(input_final.charAt(i));
        	 }
        	 
        	System.out.println();
        
        	
         }
        
		
	}

}

Posted 9-May-22 0:27am

Member 15629399

Updated 9-May-22 1:44am

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Comments

Graeme_Grant 9-May-22 6:45am

It's telling you that your index is outside the bounds of the collection

0x01AA 9-May-22 6:46am

This
for(int i=0;i<=input_final.length();i++) should be
for(int i=0;i<input_final.length();i++)

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OriginalGriff · Accepted Answer · 2022-05-09T00:56:00

In Java - as in most languages, an array or other collection is accessed via indexes which run from 0 to the number of items in the collection minus one.
So an array with 3 elements, can have valid indexes of 0, 1, and 2 only - all other values are outside the bounds of the collection because they refer to elements that don't exist.
So when your loop looks like this and input_final had three elements:

Java

for(int i=0;i<=input_final.length();i++) {

The values of i would be 0, 1, 2, and 3, which throws an exception because the final index is not in the collection.
Change the test to exclude the equality check and it only uses 0, 1, and 2 so no problem occurs:

Java

for(int i=0;i<input_final.length();i++) {

CPallini · Accepted Answer · 2022-05-09T01:44:00

Unfortunately, while correct, the Griff's suggestion doesn't completely fix your code (for instance, when i=0, your code tries to access input_final.charAt(-1); there are other issues however...). Try

Java

public static void main(String[] args)
{
  int result = 0;
  Scanner scan = new Scanner(System.in);

  HashMap< Character, Integer> roman = new HashMap< Character, Integer>();

  roman.put('I',1);
  roman.put('V',5);
  roman.put('X',10);
  roman.put('L',50);
  roman.put('C',100);
  roman.put('D',500);
  roman.put('M',1000);

  String input = scan.next();
  String input_final = input.toUpperCase();

  int next = 0;
  for(int i=0;i<input_final.length()-1;i++)
  {
    int cur =  roman.get(input_final.charAt(i));
    next =  roman.get(input_final.charAt(i+1));
    if ( cur >= next )
      result += cur;
    else
      result -= cur;
  }
  result += next;

  System.out.println(result);
}

I wrote this code to convert roman to integer but this code is throwing exception.

2 solutions

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