Java のコンストラクタとかで

ふとコードを書いてて疑問に思ったことが１つ。

public ListPattern(CasePattern[] pats) {
    this(pats, null);
}
public ListPattern(CasePattern[] pats, String tail) {
    if (pats == null)
        throw new IllegalArgumentException();
    this.pats = pats;
    this.tail = tail;
}

と

public ListPattern(CasePattern[] pats) {
    if (pats == null)
        throw new IllegalArgumentException();
    this.pats = pats;
    this.tail = null;
}
public ListPattern(CasePattern[] pats, String tail) {
    if (pats == null || tail == null)
        throw new IllegalArgumentException();
    this.pats = pats;
    this.tail = tail;
}

って、どっちのほうが正しい設計なのかな？