isEmpty() gives 20-40% more performance than "".equals().

String equals source code,

public boolean equals(Object anObject) {
        if (this == anObject) {
            return true;
        }
        if (anObject instanceof String) {
            String aString = (String)anObject;
            if (coder() == aString.coder()) {
                return isLatin1() ? StringLatin1.equals(value, aString.value)
                                  : StringUTF16.equals(value, aString.value);
            }
        }
        return false;
    }

Operator instanceOf, class casting, 3 if statements, and all this is just to start the check if the string is actually empty.

Now compare it with String.isEmpty():

public boolean isEmpty() {
    return value.length == 0;
}

If we increase the performance in the framework, automatically multiple projects get the benefit.

hacktoberfest

Comment From: snicoll

@sann3 thanks for the follow-up and for making your first contribution to Spring Boot.