可變參數之auto-boxing

章節：Initialization & Cleanup > Array initialization > Variable argument lists

以下程序會報錯：

public class OverloadingVarargs2 {
    static void f(float i, Character... args) {
        System.out.println("first");
    }
    static void f(Character... args) {
        System.out.print("second");
    }
    public static void main(String[] args) {
        f(1, ‘a’);
        f(‘a’, ‘b’);
    }
}

f('a', 'b')無法匹配。原因不得而知(char類型可以轉換爲float，也可以auto-boxing爲Character，但無法在二者間做出選擇？)

改爲一下則可以通過編譯：

public class OverloadingVarargs3 {
    static void f(float i, Character... args) {
        System.out.println("first");
    }
    static void f(char c, Character... args) {
        System.out.println("second");
    }
    public static void main(String[] args) {
        f(1, 'a');
        f('a', 'b');
    }
} 

因此，作者給出瞭如下建議：

You should generally only use a variable argument list on one version of an overloaded method. Or consider not doing it at all.