String.valueOf() behavior with char[] in List<char[]>

I was working with char[] and Collection with the below code :-

    char[] ch = { 'a', 'b', 'c' };
    List<char[]> chList = new ArrayList<char[]>();
    chList.add(new char[]{'d','e','f'});
    chList.add(new char[]{'g','h','i'});
    String chSt = String.valueOf(ch);
    String chListSt = chList.toString(); 
    System.out.println(chSt);  // outputs  abc
    System.out.println(chListSt); // outputs [[C@8288f50b, [C@b6d2b94b] instead [def, ghi]

Now what I observed above is :-

    String chSt = String.valueOf(ch);

I know the above code behaviour is correct for char[] in String.valueOf(), so for the above code abc is printed. Now consider the next line.

    String chListSt = chList.toString();

Also for the above code I know the toString() for List is defined in AbstractList and in the code of this overriden toString() I found buffer.append(next); which calls String.valueOf() method on the char[] which corresponds to next here.

So it should also print like [def, ghi], as in the direct case with char[] in the line String chSt = (String.valueOf(ch));

Why is this change in behaviour is there in both the cases while same method String.valueOf() is called on the char[]?

Jon Skeet
people
quotationmark

You're seeing the difference of calling different overloads of String.valueOf. Here's a simpler example:

public class Test {
    public static void main(String[] args) {
        char[] chars = { 'a', 'b', 'c' };
        System.out.println(String.valueOf(chars));  // abc
        Object object = chars;
        System.out.println(String.valueOf(object));  // [C@...
    }
}

The call you've found in StringBuffer or StringBuilder is just going to call String.valueOf(Object) - which then calls toString() on the array (after checking the reference isn't null). Arrays don't override toString in Java, hence the output you're getting.

people

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