How to convert Java String into byte[]?

Question

Is there any way to convert Java String to a byte[] (not the boxed Byte[])?

In trying this:

System.out.println(response.split("\r\n\r\n")[1]);
System.out.println("******");
System.out.println(response.split("\r\n\r\n")[1].getBytes().toString());

and I'm getting separate outputs. Unable to display 1st output as it is a gzip string.

<A Gzip String>
******
[B@38ee9f13

The second is an address. Is there anything I'm doing wrong? I need the result in a byte[] to feed it to gzip decompressor, which is as follows.

String decompressGZIP(byte[] gzip) throws IOException {
 java.util.zip.Inflater inf = new java.util.zip.Inflater();
 java.io.ByteArrayInputStream bytein = new java.io.ByteArrayInputStream(gzip);
 java.util.zip.GZIPInputStream gzin = new java.util.zip.GZIPInputStream(bytein);
 java.io.ByteArrayOutputStream byteout = new java.io.ByteArrayOutputStream();
 int res = 0;
 byte buf[] = new byte[1024];
 while (res >= 0) {
 res = gzin.read(buf, 0, buf.length);
 if (res > 0) {
 byteout.write(buf, 0, res);
 }
 }
 byte uncompressed[] = byteout.toByteArray();
 return (uncompressed.toString());
}

• Paddyd: stackoverflow.com/questions/5499924/…
• Mkl Rjv: Sorry, I'm trying to convert a String to bytearray and back and getting a wrong result. I'll edit it in a while and get back.
• Louis Wasserman: Your problem is that String.getBytes() does indeed return a byte array, but your belief that the toString() of a byte array will return a useful result is incorrect.

Answer 1

The object your method decompressGZIP() needs is a byte[].

So the basic, technical answer to the question you have asked is:

byte[] b = string.getBytes();
byte[] b = string.getBytes(Charset.forName("UTF-8"));
byte[] b = string.getBytes(StandardCharsets.UTF_8); // Java 7+ only

---

However the problem you appear to be wrestling with is that this doesn't display very well. Calling toString() will just give you the default Object.toString() which is the class name + memory address. In your result [B@38ee9f13, the [B means byte[] and 38ee9f13 is the memory address, separated by an @.

For display purposes you can use:

Arrays.toString(bytes);

But this will just display as a sequence of comma-separated integers, which may or may not be what you want.

To get a readable String back from a byte[], use:

String string = new String(byte[] bytes, Charset charset);

---

The reason the Charset version is favoured, is that all String objects in Java are stored internally as UTF-16. When converting to a byte[] you will get a different breakdown of bytes for the given glyphs of that String, depending upon the chosen charset.

• Michael Warner: string.getBytes("UTF-8") requires handling an UnsupportedEncodingException, while string.getBytes(Charset.forName("UTF-8")) does not. Arguing as to which method is "better" I leave as an exercise for the reader.
• Bahadır Yağan: string.getBytes(StandardCharsets.UTF_8) can also be used, and it is the same as string.getBytes(Charset.forName("UTF-8"))
• Stewart: I believe StandardCharsets is new with Java 7
• LarsH: I don't understand why this answer got so many upvotes. It may be right, but it's not very helpful ... just a couple of lines of code, most of which the OP already had, and not explaining what difference Charset.forName("UTF-8") makes or why it's important.
• Stewart: @LarsH You make a good point. To be honest, I never expected this answer to become so popular. I have now expanded the answer in order to "deserve" the upvotes. Hopefully it's an improvement.

Answer 2

 String example = "Convert Java String";
 byte[] bytes = example.getBytes();

• Anand Rockzz: Beware: getBytes() is platform dependent. Better choice is to use getBytes(StandardCharsets.UTF_8)
• D.A.H: Method getBytes is deprecated now.

Answer 3

Simply:

String abc="abcdefghight";
byte[] b = abc.getBytes();

• U. Windl: What if abc contains non US-ASCII characters, like "greater than 2³² − 1" or just binary data (like "�A���b2")?
• Teocci: this does not work for characters like � this string has only 5 characters. However when I use getBytes() i got 7 characters.
• D.A.H: Method getBytes is deprecated now.

Answer 4

Try using String.getBytes(). It returns a byte[] representing string data. Example:

String data = "sample data";
byte[] byteData = data.getBytes();

• D.A.H: Method getBytes is deprecated now.

Answer 5

You can use String.getBytes() which returns the byte[] array.

Answer 6

You might wanna try return new String(byteout.toByteArray(Charset.forName("UTF-8")))

• Trismegistos: Thanks for showing other way around from bytes to String.

Answer 7

I know I'm a little late tothe party but thisworks pretty neat (our professor gave it to us)

public static byte[] asBytes (String s) { 
 String tmp;
 byte[] b = new byte[s.length() / 2];
 int i;
 for (i = 0; i < s.length() / 2; i++) {
 tmp = s.substring(i * 2, i * 2 + 2);
 b[i] = (byte)(Integer.parseInt(tmp, 16) & 0xff);
 }
 return b; //return bytes
 }

• Palec: This decodes hex-encoded byte array. Something very different from what this question is about.

Answer 8

It is not necessary to change java as a String parameter. You have to change the c code to receive a String without a pointer and in its code:

Bool DmgrGetVersion (String szVersion);
Char NewszVersion [200];
Strcpy (NewszVersion, szVersion.t_str ());
.t_str () applies to builder c ++ 2010