Re: Wrapping primitive types in arrays

From:

ClassCastException <zjkg3d9gj56@gmail.invalid>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 5 Oct 2010 03:21:22 +0000 (UTC)

Message-ID:

<i8e5ji$nk2$1@news.eternal-september.org>

On Mon, 04 Oct 2010 03:52:38 -0700, Simone wrote:

Hello,

I need to write a method for printing an array of numbers as a string
(e.g. "(2,5,7)" ). The numbers can be int or double and I wish to write
only one method for both types so, remembering that Java wraps primitive
types into their corresponding objects (int in Integer, double in
Double) I wrote a method:

public String print( Number[] data ){ ... }

When I try to invoke the print method with an int[] or a double[]
argument, I get an error:

"The method print(Number[]) in the type MyClass is not applicable for
the arguments (int[])"

Don't use arrays. Use collections such as List<Integer> and List<Double>.
Your primitives will be autoboxed in these and you can use:

public static String print (List<? extends Number> data) {
    final StringBuilder sb = new StringBuilder();
    sb.append("(");
    boolean suppressComma = true;
    for (Number n : data) {
        if (suppressComma)
            suppressComma = false;
        else
            sb.append(",");
        sb.append(n.toString());
    }
    sb.append(")");
    return sb.toString();
}

(untested)