Regex/Java Pattern : Finding occurrences of a sub string in a string with fault tolerance of 1 or more characters

How to find occurrences of a sub string in a string with fault tolerance of 1 or more characters?

Example.

Source : John Smith

With Fault tolerance 1 Character:

• Sub String 1: Jahn should result to 1
• Sub String 2: Jonn should result to 1
• Sub String 3: Johm should result to 1
• Sub String 4: johm should result to 1 //ignore case

With Fault tolerance 2 Character:

• Sub String 1: Jann should result to 1
• Sub String 2: Joom should result to 1 and etc...

Any Regex Solution ?? Java Pattern Matching? In this case, a method like this

int countOccurrenceWithFaultTolerance(String source, String subString, int faultTolerance) {
    // TODO
    return 0;
}

Thanks in Advance.