Puzzlers with Character - Java Puzzlers: Traps, Pitfalls, and Corner Cases - page 30

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Puzzle 12: ABC
This puzzle asks the musical question, What does this program print?
public class Abc {
public static void main(String[] args) {
String letters = "ABC";
char[] numbers = { '1', '2', '3' };
System.out.println(letters + " easy as " + numbers);
}
}
Solution 12: ABC
One would hope that the program prints ABC easy as 123 . Unfortunately, it does not. If you ran it,
you found that it prints something like ABC easy as [C@16f0472 . Why is the output so ugly?
Although char is an integral type, many libraries treat it specially, because char values usually
represent characters rather than integers. For example, passing a char value to println prints a
Unicode character rather than its numerical code. Character arrays get similar special treatment:
The char[] overloading of println prints all of the characters contained in the array, and the
char[] overloadings of String.valueOf and StringBuffer.append behave analogously.
The string concatenation operator, however, is not defined in terms of these methods. It is defined
to perform string conversion on both of its operands and then to concatenate the resulting strings.
String conversion for object references, which include arrays, is defined as follows [JLS 15.18.1.1]:
If the reference is null , it is converted to the string "null" . Otherwise, the conversion is
performed as if by an invocation of the toString method of the referenced object with no