Find longest common prefix?

Question

In two strings:

\"Mary Had a Little Lamb\"
\"Mary Had a Big Lamb\"

should return

\"Mary Had a \"

Answer 1

String str1;
String str2;
// assuming str1.length > str2.length

1. a.startsWith(b) == true if not
2. in a loop keep deleting last char from str1 and repeat check of step 1.