Why am I getting a java.lang.Charsequence cannot be applied to a char error?

Question

 }else if(readUserEmail.contains('a')){
        System.out.print("true");

Why am I getting a java.lang.Charsequence cannot be applied to a char error? In this case readUserEmail is a string of an email.

Answer 1

The contains method of the String class takes a CharSequence as an argument, but you are providing a character literal as indicated by using single quotes.

Change your 'a' to "a". Double quotes are for String (which implements the CharSequence interface) and single quotes are for characters.