what is the difference between two strings in java

Question

example:
we have two strings like :
"think" and "th2inmk" the difference between the two words is 2 chars
and 2 chars is the number of different characters between them.

Answer 1

how i can solve this problem

Answer 2

Simply i want a code to check the same characters in two words and give me number of (strange) or different between them.
I hope you understand me.
Thank you

Answer 3

I talked about characters