If a char array is an Object in Java, why does printing it not display its hash code?

Question

Printing a char array does not display a hash code:

class IntChararrayTest{     public static void main(String[] args){         int intArray[] = {0,1,2};         char charArray[] = {'a','b','c'};         System.out.println(intArray);         System.out.println(charArray);     } } 

output :

[I@19e0bfd abc 

Why is the integer array printed as a hashcode and not the char array?

Answer 1

First of all, a char array is an Object in Java just like any other type of array. It is just printed differently.

PrintStream (which is the type of the System.out instance) has a special version of println for character arrays - public void println(char x[]) - so it doesn't have to call toString for that array. It eventually calls public void write(char cbuf[], int off, int len), which writes the characters of the array to the output stream.

That's why calling println for a char[] behaves differently than calling it for other types of arrays. For other array types, the public void println(Object x) overload is chosen, which calls String.valueOf(x), which calls x.toString(), which returns something like [I@19e0bfd for int arrays.

Answer 2

The int array is an array of integers where as the char array of printable characters. The printwriter has the capability to print character arrays as this is how it prints string anyway. The printwriter will therefore print them like a string, without calling the toString() method to convert it to a string. Converting an int array to a string returns a hash code, explaining why you get that output.

Take this for example:

int[] ints = new int[] { 1, 2, 3 }; char[] chars = new char[] { '1', '2', '3' } 

If you were to print both those sequences using the method you used, it would print the hash code of the int array followed by '123'.