Dead Code Warning in IF Statement

Question

I don't know why eclipse warn me "Dead Code" in this code of mine:

    PreparedStatement p = conn.prepareStatement("SELECT name FROM user WHERE age = ? , city = ?");
    p.setInt(1, (String) parameters.get("age"));
    p.setString(2, (String) parameters.get("city"));

    if (p == null) {
        log.warn("User is not available");
        return results;
    }

the warning was in the log, can anybody tell me the reason of this? thank you.

Answer 1

p can not be null at that point, simply because you already called setInt and setString on p and if it were null there, then it would have thrown a NullPointerException , thus never reaching your if .

Also note that according to its documentation , preparedStatement can't ever return null . It can only return a valid statement or throw an exception. In the latter case your if will also not be reached. That fact, however, is not checked by the compiler (because a broken implementation of prepareStatement could theoretically return null ).

Answer 2

You need to do that null check before you call any method on p . If p is null , it will never reach that line.

Answer 3

if p is null then in the second line itself there will be `NullPointerException' thrown.

change the code like below

PreparedStatement p = conn.prepareStatement("SELECT name FROM user WHERE age = ? , city = ?");
if(p != null){
    p.setInt(1, (String) parameters.get("age"));
    p.setString(2, (String) parameters.get("city"));
}else{
    log.warn("User is not available");
    return results;
}

or bring the if loop before using p

PreparedStatement p = conn.prepareStatement("SELECT name FROM user WHERE age = ? , city = ?");
if (p == null) {
    log.warn("User is not available");
    return results;
}
p.setInt(1, (String) parameters.get("age"));
p.setString(2, (String) parameters.get("city"));