Program to extract a portion of a character string and print the extracted string

/* Program to extract a portion of a character string and print the extracted string */

import java.io.DataInputStream;     // to load DataInputStream class        

class P21
{
    public static void main(String args[ ])
    {
        String str1 = new String();
        String str2 = new String();
        int m=0,n=0;
        DataInputStream in = new DataInputStream(System.in);

        try
        {
            System.out.print("Enter String : ");
            str1 = in.readLine();
            System.out.println(" String is : "+str1);
            System.out.print("Enter no. of chracters to be extracted from string : ");
            m = Integer.parseInt(in.readLine());
            System.out.print("Enter starting index : ");
            n = Integer.parseInt(in.readLine());
        }
        catch(Exception e) {  System.out.println("I/O Error");   }

       
        str2=str1.substring(n,(m+n));
        System.out.println(" Extracted String is : "+str2);
    }
}