Develop Reference

How to convert String to byte without changing?

I need a solution to convert String to byte array without changing like this:
Input:
String s="Test";
Output:
String s="Test";
byte[] b="Test";
When I use
s.getBytes();
then the reply is
"[B#428b76b8"
but I want the reply to be
"Test"

You should always make sure serialization and deserialization are using the same character set, this maps characters to byte sequences and vice versa. By default String.getBytes() and new String(bytes) uses the default character set which could be Locale specific.
Use the getBytes(Charset) overload
byte[] bytes = s.getBytes(Charset.forName("UTF-8"));
Use the new String(bytes, Charset) constructor
String andBackAgain = new String(bytes, Charset.forName("UTF-8"));
Also Java 7 added the java.nio.charset.StandardCharsets class, so you don't need to use dodgy String constants anymore
byte[] bytes = s.getBytes(StandardCharsets.UTF_8);
String andBackAgain = new String(bytes, StandardCharsets.UTF_8);

You can revert back using
String originalString = new String(b, "UTF-8");
That should get you back your original string. You don't want the bytes printed out directly.

You may try the following code snippet -
String string = "Sample String";
byte[] byteArray = string.getBytes();

In general that's probably not what you want to do, unless you're serializing or transmitting the data. Also, Java strings are UTF-16 rather than UTF-8, which what more like what you're expecting. If you really do want/need this then this should work:
String str = "Test";
byte[] raw = str.getBytes(new Charset("UTF-8", null));

In Java Is it possible to convert character set 1047 into another character set, say 500?

I have a program which reads a message from MQ. the character set is 1047. Since my java version is very old it doesn't support thus character set.
Is it possible to change this string into char set 500 in the program after receiving but before reading.
For eg:
public void fun (String str){ //str in char set 1047. **1047 is not supported in my system**
/* can I convert str into char set 500 here. Convert it into byte stream and then back to string. Something like this */
byte [] b=str.getBytes();
ByteArrayOutputStream baos = null;
try{
baos = new ByteArrayOutputStream();
baos.write(b);
String str = baos.toString("IBM-500");
System.out.println(str);
}

byte [] b=str.getBytes(); //will convert string(encoding could only be Unicode in jvm) to bytes using file.encoding. You should check whether the str contains correct information, if so, you need not care the 1047 encoding, just run str.getBytes("IBM-500"), you will get the 500 encoded bytes. Again, String object only use Unicode, if you convert string to bytes, the encoding matters the result bytes array.

How to convert UTF8 string to UTF16

I'm getting a UTF8 string by processing a request sent by a client application. But the string is really UTF16. What can I do to get it into my local string is a letter followed by \0 character? I need to convert that String into UTF16.
Sample received string: S\0a\0m\0p\0l\0e (UTF8).
What I want is : Sample (UTF16)
FileItem item = (FileItem) iter.next();
String field = "";
String value = "";
if (item.isFormField()) {
try{
value=item.getString();
System.out.println("====" + value);
}

The bytes from the server are not UTF-8 if they look like S\0a\0m\0p\0l\0e. They are UTF-16. You can convert UTF16 bytes to a Java String with:
byte[] bytes = ...
String string = new String(bytes, "UTF-16");
Or you can use UTF-16LE or UTF-16BE as the character set name if you know the endian-ness of the byte stream coming from the server.
If you've already (mistakenly) constructed a String from the bytes as if it were UTF-8, you can convert to UTF-16 with:
string = new String(string.getBytes("UTF-8"), "UTF-16");
However, as JB Nizet points out, this round trip (bytes -> UTF-8 string -> bytes) is potentially lossy if the bytes weren't valid UTF-8 to start with.

I propose the following solution:
NSString *line_utf16[ENOUGH_MEMORY_SIZE];
line_utf16= [NSString stringWithFormat: #"%s", line_utf8];
ENOUGH_MEMORY_SIZE is at least twice exceeds memory used for line_utf8
I suppose memory for
line_utf16
has to be dynamically or statically allocated at least twice of the size of
line_utf8.
If you run into similar problem please add a couple of sentences!

Encode String to UTF-8

I have a String with a "ñ" character and I have some problems with it. I need to encode this String to UTF-8 encoding. I have tried it by this way, but it doesn't work:
byte ptext[] = myString.getBytes();
String value = new String(ptext, "UTF-8");
How do I encode that string to utf-8?

How about using
ByteBuffer byteBuffer = StandardCharsets.UTF_8.encode(myString)

String objects in Java use the UTF-16 encoding that can't be modified*.
The only thing that can have a different encoding is a byte[]. So if you need UTF-8 data, then you need a byte[]. If you have a String that contains unexpected data, then the problem is at some earlier place that incorrectly converted some binary data to a String (i.e. it was using the wrong encoding).
* As a matter of implementation, String can internally use a ISO-8859-1 encoded byte[] when the range of characters fits it, but that is an implementation-specific optimization that isn't visible to users of String (i.e. you'll never notice unless you dig into the source code or use reflection to dig into a String object).

In Java7 you can use:
import static java.nio.charset.StandardCharsets.*;
byte[] ptext = myString.getBytes(ISO_8859_1);
String value = new String(ptext, UTF_8);
This has the advantage over getBytes(String) that it does not declare throws UnsupportedEncodingException.
If you're using an older Java version you can declare the charset constants yourself:
import java.nio.charset.Charset;
public class StandardCharsets {
public static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
public static final Charset UTF_8 = Charset.forName("UTF-8");
//....
}

Use byte[] ptext = String.getBytes("UTF-8"); instead of getBytes(). getBytes() uses so-called "default encoding", which may not be UTF-8.

A Java String is internally always encoded in UTF-16 - but you really should think about it like this: an encoding is a way to translate between Strings and bytes.
So if you have an encoding problem, by the time you have String, it's too late to fix. You need to fix the place where you create that String from a file, DB or network connection.

You can try this way.
byte ptext[] = myString.getBytes("ISO-8859-1");
String value = new String(ptext, "UTF-8");

In a moment I went through this problem and managed to solve it in the following way
first i need to import
import java.nio.charset.Charset;
Then i had to declare a constant to use UTF-8 and ISO-8859-1
private static final Charset UTF_8 = Charset.forName("UTF-8");
private static final Charset ISO = Charset.forName("ISO-8859-1");
Then I could use it in the following way:
String textwithaccent="Thís ís a text with accent";
String textwithletter="Ñandú";
text1 = new String(textwithaccent.getBytes(ISO), UTF_8);
text2 = new String(textwithletter.getBytes(ISO),UTF_8);

String value = new String(myString.getBytes("UTF-8"));
and, if you want to read from text file with "ISO-8859-1" encoded:
String line;
String f = "C:\\MyPath\\MyFile.txt";
try {
BufferedReader br = Files.newBufferedReader(Paths.get(f), Charset.forName("ISO-8859-1"));
while ((line = br.readLine()) != null) {
System.out.println(new String(line.getBytes("UTF-8")));
}
} catch (IOException ex) {
//...
}

I have use below code to encode the special character by specifying encode format.
String text = "This is an example é";
byte[] byteText = text.getBytes(Charset.forName("UTF-8"));
//To get original string from byte.
String originalString= new String(byteText , "UTF-8");

A quick step-by-step guide how to configure NetBeans default encoding UTF-8. In result NetBeans will create all new files in UTF-8 encoding.
NetBeans default encoding UTF-8 step-by-step guide
Go to etc folder in NetBeans installation directory
Edit netbeans.conf file
Find netbeans_default_options line
Add -J-Dfile.encoding=UTF-8 inside quotation marks inside that line
(example: netbeans_default_options="-J-Dfile.encoding=UTF-8")
Restart NetBeans
You set NetBeans default encoding UTF-8.
Your netbeans_default_options may contain additional parameters inside the quotation marks. In such case, add -J-Dfile.encoding=UTF-8 at the end of the string. Separate it with space from other parameters.
Example:
netbeans_default_options="-J-client -J-Xss128m -J-Xms256m
-J-XX:PermSize=32m -J-Dapple.laf.useScreenMenuBar=true -J-Dapple.awt.graphics.UseQuartz=true -J-Dsun.java2d.noddraw=true -J-Dsun.java2d.dpiaware=true -J-Dsun.zip.disableMemoryMapping=true -J-Dfile.encoding=UTF-8"
here is link for Further Details

This solved my problem
String inputText = "some text with escaped chars"
InputStream is = new ByteArrayInputStream(inputText.getBytes("UTF-8"));

Java InputStream encoding/charset

Running the following (example) code
import java.io.*;
public class test {
public static void main(String[] args) throws Exception {
byte[] buf = {-27};
InputStream is = new ByteArrayInputStream(buf);
BufferedReader r = new BufferedReader(
new InputStreamReader(is, "ISO-8859-1"));
String s = r.readLine();
System.out.println("test.java:9 [byte] (char)" + (char)s.getBytes()[0] +
" (int)" + (int)s.getBytes()[0]);
System.out.println("test.java:10 [char] (char)" + (char)s.charAt(0) +
" (int)" + (int)s.charAt(0));
System.out.println("test.java:11 string below");
System.out.println(s);
System.out.println("test.java:13 string above");
}
}
gives me this output
test.java:9 [byte] (char)? (int)63
test.java:10 [char] (char)? (int)229
test.java:11 string below
?
test.java:13 string above
How do I retain the correct byte value (-27) in the line-9 printout? And consequently receive the expected output of the System.out.println(s) command (å).

If you want to retain byte values, don't use a Reader at all, ideally. To represent arbitrary binary data in text and convert it back to binary data later, you should use base16 or base64 encoding.
However, to explain what's going on, when you call s.getBytes() that's using the default character encoding, which apparently doesn't include Unicode character U+00E5.
If you call s.getBytes("ISO-8859-1") everywhere instead of s.getBytes() I suspect you'll get back the right byte value... but relying on ISO-8859-1 for this is kinda dirty IMO.

As noted, getBytes() (no-arguments) uses the Java platform default encoding, which may not be ISO-8859-1. Simply printing it should work, provided your terminal and the default encoding match and support the character. For instance, on my system, the terminal and default Java encoding are both UTF-8. The fact that you're seeing a '?' indicates that yours don't match or å is not supported.
If you want to manually encode to UTF-8 on your system, do:
String s = r.readLine();
byte[] utf8Bytes = s.getBytes("UTF-8");
It should give a byte array with {-61, -91}.