Unreachable code compiler error [duplicate]

Answer 1

Will it break the Java bytecode somehow, is it to protect the programmer or is it something else?

This is not required as far as Java/JVM is concerned. The sole purpose of this compilation error is to avoid silly programmer mistakes. Consider the following JavaScript code:

function f() {
    return 
        {
            answer: 42
        }
}

This function returns undefined as the JavaScript engine adds semicolon at the end of the line and ignores dead-code (as it thinks). Java compiler is more clever and when it discoveres you are doing something clearly and obviously wrong, it won't let you do this. There is no way on earth you intended to have dead-code. This somehow fits into the Java premise of being a safe language.