CODEWITHSUNDEEP
javaarrayscharoutput
stephenwade
stephenwade

Reputation: 1189

Java: println with char array gives gibberish

Here's the problem. This code:

String a = "0000";
 System.out.println(a);
char[] b = a.toCharArray();
 System.out.println(b);

returns

0000
0000


But this code:

String a = "0000";
 System.out.println("String a: " + a);
char[] b = a.toCharArray();
 System.out.println("char[] b: " + b);

returns

String a: 0000
char[] b: [C@56e5b723


What in the world is going on? Seems there should be a simple enough solution, but I can't seem to figure it out.

Upvotes: 28

Views: 43991

Answers (6)

Akriti Singh
Akriti Singh

Reputation: 1

private void print(char[] arr) {
    try {
        PrintStream stream
                = new PrintStream(System.out);
        stream.println(arr);
        stream.flush();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

Upvotes: 0

user1991275
user1991275

Reputation: 100

Use 3:e row!

Scanner input = new Scanner(System.in);
char[] txt = input.next().toCharArray();
System.out.println((char[])txt);

Upvotes: 2

chenyun
chenyun

Reputation: 71

System.out.println("char[] b: " + b);

This is just like 

System.out.println(("char[] b: " + b.toString());

You can look up "Object.toString()"

Upvotes: 5

millimoose
millimoose

Reputation: 39950

An array's toString() method (which is what's called when you do "..." + b) is only meant to give debugging output. There isn't a special case where a char[]'s toString() will give you the original string - arrays of all types have the same toString() implementation.

If you want to get the original string from the char array, use:

String a2 = new String(b);

Upvotes: 4

Doug Moscrop
Doug Moscrop

Reputation: 4544

When you say

System.out.println(b);

It results in a call to print(char[] s) then println()

The JavaDoc for print(char[] s) says:

Print an array of characters. The characters are converted into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.

So it performs a byte-by-byte print out.

When you say

System.out.println("char[] b: " + b);

It results in a call to print(String), and so what you're actually doing is appending to a String an Object which invokes toString() on the Object -- this, as with all Object by default, and in the case of an Array, prints the value of the reference (the memory address).

You could do:

System.out.println("char[] b: " + new String(b));

Note that this is "wrong" in the sense that you're not paying any mind to encoding and are using the system default. Learn about encoding sooner rather than later.

Upvotes: 31

shazin
shazin

Reputation: 21883

Use 

System.out.println("char[] b: " + Arrays.toString(b));

The gibrish you get is the Class name followed by the memory address of the object. Problem occurs when you try to append b with a string char[] b: in this case the char array b.toString() method is called thus [C@56e5b723 is printed.

[ indicates that it is an array C indicates the class in this case char @56e5b723 indicates the memory location

Upvotes: 5

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