Question

so basically, a user inputs 2 strings ( CATSATONTHEMAT AT ) and we need to count how many time the second string appears in the first string ( so the answer here is 3 )

this is what I have so far, and it keeps saying

“Exception in thread “main” java.lang.StringIndexOutOfBoundsException: String index out of range: 81223
at java.lang.String.substring(Unknown Source)
at practice.main(practice.java:60)”

any help would be appreciated! I just can’t see to find where I went wrong

    String s = scan.next(); // CATSATONTHEMAT
    String t = scan.next(); // AT

    int j= 0;

    for ( int i = 0 ; i < s.length(); i++){
        int k = t.length();
        String newstring = s.substring(i,i+k); // I printed this and the substring works so the if statement might not be working..

        if(newstring.equals(t))
            j++;   // if the new substring equal "AT" then add 1
        }

    System.out.printf("%d", j);  // suppose to print just 3

Answer 1

The outOfBounds exception happens when i is near the end of s and k takes you passed the end of the string.

You need to change the loop to only go up to s.length()-t.length()

for ( int i = 0 ; i < s.length()-t.length(); i++){

I would also recommend bringing the int k = t.length() out of the for loop. You don’t need to assign that every iteration as it should be the same for every iteration.