Java get default charset

How to Get and Set Default Character Encoding or Charset in Java?

In Java, the default character encoding is determined by the ‘file.encoding’ which is a system property and is usually set by the operating system or the JVM. However, sometimes a Java programmer may need to get or set the default character encoding programmatically for various reasons. For this purpose, the ‘java.nio.charset’ package provides various classes and methods. In this article, we are going to learn the different ways to get and set default character encoding or charset.

Get and Set Default Character Encoding or Charset in Java

First, let’s discuss what is default character encoding or charset.

Default Character Encoding

Character encoding or charset is a way of mapping a set of characters to a sequence of bytes. But, why do we need to map, here is the answer. We know that the data in a computer system is represented in the form of bytes but we interact with computers using a sequence of characters called String. Therefore, we need to map byte into characters so that the JVM can recognize which set of bytes represent which character. Furthermore, Different character encodings may use different numbers of bytes to represent the same character or may support different sets of characters altogether. For example, ASCII is a 7-bit encoding that can represent 128 characters, while UTF-8 is a variable-length encoding that can represent over a million characters.

To Get Default Character Encoding or Charset

We are going to use the following ways in our example program to find the default character encoding or charset:

• file.encoding: It is an attribute of ‘System.getProperty()’ method that returns the value of charset.
• defaultCharset() method: It is a method of ‘java.nio.charset‘ package that is used for retrieving the default character encoding of Java Virtual Machine.
• getEncoding() method: It is a method of the ‘java.io.FileReader‘ class that is used for retrieving the default character encoding of streams.

Example 1

In the following example, we will demonstrate the use of ‘file.encoding‘ attribute and ‘defaultCharset()’ method in getting default character encoding.

import java.nio.charset.Charset; public class GetDefaultCharset < public static void main(String[] args) < // to get the default charset Charset defaultCharset1 = Charset.defaultCharset(); String defaultCharset2 = System.getProperty("file.encoding"); // printing the name of default charset System.out.println("Default charset1: " + defaultCharset1.name()); System.out.println("Default charset2: " + defaultCharset2); >>

Output

Default charset1: UTF-8 Default charset2: UTF-8

Example 2

In this example, we will create a byte array of characters and pass them as a stream to check its current character encoding using the ‘getEncoding()’ method.

import java.io.*; import java.nio.charset.Charset; public class GetDefaultCharset < public static void main(String args[]) < // creating an array of byte byte[] chAray = ; // converting the array into stream InputStream inStrm = new ByteArrayInputStream(chAray); // reading the stream InputStreamReader strmRdr = new InputStreamReader(inStrm); // checking and printing the charset String defaultCharset = strmRdr.getEncoding(); System.out.println("Default charset: " + defaultCharset); > >

Output

To Set Default Character Encoding or Charset

We can use the ‘System.setProperty()’ by passing the ‘file.encoding’ attribute along with a type of Charset to set the default character encoding.

Example 3

The following example illustrates how to set the default character encoding in Java.

import java.nio.charset.Charset; public class SetDefaultCharset < public static void main(String[] args) < // setting the default charset to ISO-8859-1 System.setProperty("file.encoding", "ISO-8859-1"); // to get the new default charset Charset defaultCharset = Charset.defaultCharset(); // printing the name and aliases of default charset System.out.println("Default charset: " + defaultCharset.name()); System.out.println("Aliases: " + defaultCharset.aliases()); >>

Output

Default charset: UTF-8 Aliases: [unicode-1-1-utf-8, UTF8]

Conclusion

In this article, we have learned various ways to get and set default character encoding in Java with the help of example programs. First, we understood the basics of default Charset and then, discussed three Java programs that show the practical implementation of discussed ways of getting and setting default Charset.

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Class Charset

A named mapping between sequences of sixteen-bit Unicode code units and sequences of bytes. This class defines methods for creating decoders and encoders and for retrieving the various names associated with a charset. Instances of this class are immutable.

This class also defines static methods for testing whether a particular charset is supported, for locating charset instances by name, and for constructing a map that contains every charset for which support is available in the current Java virtual machine. Support for new charsets can be added via the service-provider interface defined in the CharsetProvider class.

All of the methods defined in this class are safe for use by multiple concurrent threads.

Charset names

• The uppercase letters ‘A’ through ‘Z’ ( ‘\u0041’ through ‘\u005a’ ),
• The lowercase letters ‘a’ through ‘z’ ( ‘\u0061’ through ‘\u007a’ ),
• The digits ‘0’ through ‘9’ ( ‘\u0030’ through ‘\u0039’ ),
• The dash character ‘-‘ ( ‘\u002d’ , HYPHEN-MINUS),
• The plus character ‘+’ ( ‘\u002b’ , PLUS SIGN),
• The period character ‘.’ ( ‘\u002e’ , FULL STOP),
• The colon character ‘:’ ( ‘\u003a’ , COLON), and
• The underscore character ‘_’ ( ‘\u005f’ , LOW LINE).

Every charset has a canonical name and may also have one or more aliases. The canonical name is returned by the name method of this class. Canonical names are, by convention, usually in upper case. The aliases of a charset are returned by the aliases method.

Some charsets have an historical name that is defined for compatibility with previous versions of the Java platform. A charset’s historical name is either its canonical name or one of its aliases. The historical name is returned by the getEncoding() methods of the InputStreamReader and OutputStreamWriter classes.

If a charset listed in the IANA Charset Registry is supported by an implementation of the Java platform then its canonical name must be the name listed in the registry. Many charsets are given more than one name in the registry, in which case the registry identifies one of the names as MIME-preferred. If a charset has more than one registry name then its canonical name must be the MIME-preferred name and the other names in the registry must be valid aliases. If a supported charset is not listed in the IANA registry then its canonical name must begin with one of the strings «X-» or «x-» .

The IANA charset registry does change over time, and so the canonical name and the aliases of a particular charset may also change over time. To ensure compatibility it is recommended that no alias ever be removed from a charset, and that if the canonical name of a charset is changed then its previous canonical name be made into an alias.

Standard charsets

Every implementation of the Java platform is required to support the following standard charsets. Consult the release documentation for your implementation to see if any other charsets are supported. The behavior of such optional charsets may differ between implementations.

Description of standard charsets

Charset	Description
US-ASCII	Seven-bit ASCII, a.k.a. ISO646-US , a.k.a. the Basic Latin block of the Unicode character set
ISO-8859-1	ISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1
UTF-8	Eight-bit UCS Transformation Format
UTF-16BE	Sixteen-bit UCS Transformation Format, big-endian byte order
UTF-16LE	Sixteen-bit UCS Transformation Format, little-endian byte order
UTF-16	Sixteen-bit UCS Transformation Format, byte order identified by an optional byte-order mark

The UTF-8 charset is specified by RFC 2279; the transformation format upon which it is based is specified in Amendment 2 of ISO 10646-1 and is also described in the Unicode Standard.

The UTF-16 charsets are specified by RFC 2781; the transformation formats upon which they are based are specified in Amendment 1 of ISO 10646-1 and are also described in the Unicode Standard.

• When decoding, the UTF-16BE and UTF-16LE charsets interpret the initial byte-order marks as a ZERO-WIDTH NON-BREAKING SPACE; when encoding, they do not write byte-order marks.
• When decoding, the UTF-16 charset interprets the byte-order mark at the beginning of the input stream to indicate the byte-order of the stream but defaults to big-endian if there is no byte-order mark; when encoding, it uses big-endian byte order and writes a big-endian byte-order mark.

Every instance of the Java virtual machine has a default charset, which may or may not be one of the standard charsets. The default charset is determined during virtual-machine startup and typically depends upon the locale and charset being used by the underlying operating system.

The StandardCharsets class defines constants for each of the standard charsets.

Terminology

The name of this class is taken from the terms used in RFC 2278. In that document a charset is defined as the combination of one or more coded character sets and a character-encoding scheme. (This definition is confusing; some other software systems define charset as a synonym for coded character set.)

A coded character set is a mapping between a set of abstract characters and a set of integers. US-ASCII, ISO 8859-1, JIS X 0201, and Unicode are examples of coded character sets.

Some standards have defined a character set to be simply a set of abstract characters without an associated assigned numbering. An alphabet is an example of such a character set. However, the subtle distinction between character set and coded character set is rarely used in practice; the former has become a short form for the latter, including in the Java API specification.

A character-encoding scheme is a mapping between one or more coded character sets and a set of octet (eight-bit byte) sequences. UTF-8, UTF-16, ISO 2022, and EUC are examples of character-encoding schemes. Encoding schemes are often associated with a particular coded character set; UTF-8, for example, is used only to encode Unicode. Some schemes, however, are associated with multiple coded character sets; EUC, for example, can be used to encode characters in a variety of Asian coded character sets.

When a coded character set is used exclusively with a single character-encoding scheme then the corresponding charset is usually named for the coded character set; otherwise a charset is usually named for the encoding scheme and, possibly, the locale of the coded character sets that it supports. Hence US-ASCII is both the name of a coded character set and of the charset that encodes it, while EUC-JP is the name of the charset that encodes the JIS X 0201, JIS X 0208, and JIS X 0212 coded character sets for the Japanese language.

The native character encoding of the Java programming language is UTF-16. A charset in the Java platform therefore defines a mapping between sequences of sixteen-bit UTF-16 code units (that is, sequences of chars) and sequences of bytes.

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