> For the complete documentation index, see [llms.txt](https://www.pranaypourkar.co.in/the-programmers-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.pranaypourkar.co.in/the-programmers-guide/java/java-packages/core-packages/java.nio/java.nio.charset.md). # java.nio.charset ## About The `java.nio.charset` package provides classes and interfaces for character encoding and decoding. It is part of the Java NIO (New I/O) package introduced in Java 1.4 to provide non-blocking I/O operations, among other features. Understanding character sets is crucial for applications dealing with text processing, file I/O, network communication, and internationalization. ## **Charset** (java.nio.charset.Charset) Represents a named mapping between sequences of sixteen-bit Unicode characters and sequences of bytes. It defines methods for encoding, decoding, and working with character sets. **Static Methods** * `static Charset forName(String charsetName)`: Returns a charset object for the given charset name. * `static Charset defaultCharset()`: Returns the default charset of this Java virtual machine. * `static SortedMap availableCharsets()`: Returns a map of available charsets. * `static boolean isSupported(String charsetName)`: Tells whether the named charset is supported. **Methods** * `boolean contains(Charset cs)`: Tells whether or not this charset contains the given charset. * `boolean canEncode()`: Tells whether or not this charset supports encoding. * `String name()`: Returns the canonical name of this charset. * `Set aliases()`: Returns a set containing this charset's aliases. * `String displayName()`: Returns a string that is the canonical name of this charset. * `String displayName(Locale locale)`: Returns a localized string that is the canonical name of this charset. * `boolean isRegistered()`: Tells whether or not this charset is known by its canonical name. * `CharsetEncoder newEncoder()`: Constructs a new encoder for this charset. * `CharsetDecoder newDecoder()`: Constructs a new decoder for this charset. * `ByteBuffer encode(CharBuffer cb)`: Convenience method that encodes Unicode characters into bytes. * `ByteBuffer encode(String str)`: Convenience method that encodes a string into bytes. * `CharBuffer decode(ByteBuffer bb)`: Convenience method that decodes bytes into Unicode characters. * `int compareTo(Charset that)`: Compares this charset to another. ## **CharsetDecoder** (java.nio.charset.CharsetDecoder) Converts a byte sequence into a sequence of sixteen-bit Unicode characters. **Methods** * `Charset charset()`: Returns the charset that created this decoder. * `CharsetDecoder onMalformedInput(CodingErrorAction newAction)`: Changes the action for malformed-input errors. * `CharsetDecoder onUnmappableCharacter(CodingErrorAction newAction)`: Changes the action for unmappable-character errors. * `CodingErrorAction malformedInputAction()`: Returns the current malformed-input action. * `CodingErrorAction unmappableCharacterAction()`: Returns the current unmappable-character action. * `CharsetDecoder replaceWith(String newReplacement)`: Changes this decoder's replacement value. * `String replacement()`: Returns this decoder's replacement value. * `boolean isAutoDetecting()`: Tells whether or not this decoder implements an auto-detecting charset. * `boolean isCharsetDetected()`: Tells whether or not a charset has yet been detected by this decoder. * `Charset detectedCharset()`: Returns the charset detected by this decoder, if any. * `CoderResult decode(ByteBuffer in, CharBuffer out, boolean endOfInput)`: Decodes one or more bytes into one or more characters. * `CoderResult flush(CharBuffer out)`: Flushes this decoder. * `CharsetDecoder reset()`: Resets this decoder, clearing any internal state. ## **CharsetEncoder** (java.nio.charset.CharsetEncoder) Converts a sequence of sixteen-bit Unicode characters into a byte sequence. **Methods** * `Charset charset()`: Returns the charset that created this encoder. * `CharsetEncoder onMalformedInput(CodingErrorAction newAction)`: Changes the action for malformed-input errors. * `CharsetEncoder onUnmappableCharacter(CodingErrorAction newAction)`: Changes the action for unmappable-character errors. * `CodingErrorAction malformedInputAction()`: Returns the current malformed-input action. * `CodingErrorAction unmappableCharacterAction()`: Returns the current unmappable-character action. * `CharsetEncoder replaceWith(byte[] newReplacement)`: Changes this encoder's replacement value. * `byte[] replacement()`: Returns this encoder's replacement value. * `float averageBytesPerChar()`: Returns this encoder's average bytes-per-character. * `float maxBytesPerChar()`: Returns this encoder's maximum bytes-per-character. * `CoderResult encode(CharBuffer in, ByteBuffer out, boolean endOfInput)`: Encodes one or more characters into one or more bytes. * `CoderResult flush(ByteBuffer out)`: Flushes this encoder. * `CharsetEncoder reset()`: Resets this encoder, clearing any internal state. * `boolean canEncode(char c)`: Tells whether or not this encoder can encode the given character. * `boolean canEncode(CharSequence cs)`: Tells whether or not this encoder can encode the given character sequence. ## **CodingErrorAction** (java.nio.charset.CodingErrorAction) Describes actions to be taken when encoding/decoding errors occur. Actions include `IGNORE`, `REPLACE`, and `REPORT`. **Static Variables** * `static CodingErrorAction IGNORE`: Action indicating that a coding error is to be ignored. * `static CodingErrorAction REPLACE`: Action indicating that a coding error is to be handled by dropping the erroneous input and replacing it with the current replacement byte or character sequence. * `static CodingErrorAction REPORT`: Action indicating that a coding error is to be reported, either by returning a `CoderResult` object or by throwing a `CharacterCodingException`, depending upon the method implementing the coding process. ### **StandardCharsets** (java.nio.charset.StandardCharsets) Defines constants for standard character sets such as UTF-8, UTF-16, ISO-8859-1, etc. **Static Variables** * `static Charset US_ASCII`: Seven-bit ASCII, a.k.a. ISO646-US, a.k.a. the Basic Latin block of the Unicode character set. * `static Charset ISO_8859_1`: ISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1. * `static Charset UTF_8`: Eight-bit UCS Transformation Format. * `static Charset UTF_16BE`: Sixteen-bit UCS Transformation Format, big-endian byte order. * `static Charset UTF_16LE`: Sixteen-bit UCS Transformation Format, little-endian byte order. * `static Charset UTF_16`: Sixteen-bit UCS Transformation Format, byte order identified by an optional byte-order mark. ## UnsupportedCharsetException (java.nio.charset.UnsupportedCharsetException) **Constructor** * `UnsupportedCharsetException(String charsetName)`: Constructs an instance of this class. **Methods** * `String getCharsetName()`: Retrieves the name of the unsupported charset. ## Examples ### Encoding and Decoding Strings ```java import java.nio.charset.Charset; import java.nio.charset.StandardCharsets; import java.nio.ByteBuffer; import java.nio.CharBuffer; public class CharsetExample { public static void main(String[] args) { String input = "Hello, World!"; Charset charset = StandardCharsets.UTF_8; // Encoding ByteBuffer byteBuffer = charset.encode(input); System.out.println("Encoded ByteBuffer: " + byteBuffer); // Decoding CharBuffer charBuffer = charset.decode(byteBuffer); String output = charBuffer.toString(); System.out.println("Decoded String: " + output); } } ```
### Handling Encoding or Decoding Errors ```java import java.nio.charset.Charset; import java.nio.charset.CharsetDecoder; import java.nio.charset.CharsetEncoder; import java.nio.charset.CodingErrorAction; import java.nio.ByteBuffer; import java.nio.CharBuffer; public class ErrorHandlingExample { public static void main(String[] args) { Charset charset = Charset.forName("US-ASCII"); CharsetEncoder encoder = charset.newEncoder(); CharsetDecoder decoder = charset.newDecoder(); encoder.onMalformedInput(CodingErrorAction.REPLACE); encoder.onUnmappableCharacter(CodingErrorAction.REPLACE); decoder.onMalformedInput(CodingErrorAction.REPLACE); decoder.onUnmappableCharacter(CodingErrorAction.REPLACE); String input = "Hello, World! \u00A9"; ByteBuffer byteBuffer = encoder.encode(CharBuffer.wrap(input)); CharBuffer charBuffer = decoder.decode(byteBuffer); String output = charBuffer.toString(); System.out.println("Original String: " + input); System.out.println("Encoded and Decoded String: " + output); } } ```
### Listing Available Charsets ```java import java.nio.charset.Charset; import java.util.SortedMap; public class ListCharsets { public static void main(String[] args) { SortedMap charsets = Charset.availableCharsets(); for (String charsetName : charsets.keySet()) { System.out.println(charsetName); } } } ```
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