if statements

import java.util.function.Predicate;
import java.util.regex.Pattern;

class Bob {

    final private static Pattern isAlpha = Pattern.compile("[a-zA-Z]");
    final private static Predicate < String > isShout = msg -> isAlpha.matcher(msg).find() && msg == msg.toUpperCase();

    public String hey(String message) {
        var speech = message.trim();
        if (speech.isEmpty()) {
            return "Fine. Be that way!";
        }
        var questioning = speech.endsWith("?");
        var shouting = isShout.test(speech);
        if (questioning) {
            if (shouting) {
                return "Calm down, I know what I'm doing!";
            }
            return "Sure.";
        }
        if (shouting) {
            return "Whoa, chill out!";
        }
        return "Whatever.";
    }
}

In this approach you have a series of if statements using the private methods to evaluate the conditions. As soon as the right condition is found, the correct response is returned.

Note that there are no else if or else statements. If an if statement can return, then an else if or else is not needed. Execution will either return or will continue to the next statement anyway.

The String trim() method is applied to the input to eliminate any whitespace at either end of the input. If the string has no characters left, it returns the response for saying nothing.

A Pattern is defined to look for at least one English alphabetic character.

The first half of the isShout Predicate

isAlpha.matcher(msg).find() && msg == msg.toUpperCase();

is constructed from the Pattern matcher() method and the Matcher find() method to ensure there is at least one letter character in the String. This is because the second half of the condition tests that the uppercased input is the same as the input. If the input were only "123" it would equal itself uppercased, but without letters it would not be a shout.

A question is determined by use of the endsWith() method to see if the input ends with a question mark.

Shortening

When the body of an if statement is a single line, both the test expression and the body could be put on the same line, like so

if (speech.isEmpty()) return "Fine. Be that way!";

or the body could be put on a separate line without curly braces

if (speech.isEmpty())
    return "Fine. Be that way!";

However, the Java Coding Conventions advise to always use curly braces for if statements, which helps to avoid errors. Your team may choose to overrule them at its own risk.