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InputStreamReader (Java SE 26 & JDK 26)

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java.lang.Object

java.io.Reader

java.io.InputStreamReader

All Implemented Interfaces: Closeable, AutoCloseable, Readable Direct Known Subclasses: FileReader

public class InputStreamReader extends Reader

An InputStreamReader is a bridge from byte streams to character streams: It reads bytes and decodes them into characters using a specified charset. The charset that it uses may be specified by name or may be given explicitly, or the default charset may be used.

Each invocation of one of an InputStreamReader's read() methods may cause one or more bytes to be read from the underlying byte-input stream. To enable the efficient conversion of bytes to characters, more bytes may be read ahead from the underlying stream than are necessary to satisfy the current read operation.

For top efficiency, consider wrapping an InputStreamReader within a BufferedReader. For example:

Copy BufferedReader in = new BufferedReader(new InputStreamReader(anInputStream));

To read from System.in, use the system property value stdin.encoding as the Charset:

Copy new InputStreamReader(System.in, System.getProperty("stdin.encoding"));

Since: 1.1 See Also:

Field Summary

Fields declared in class Reader
lock

Modifier and Type

Field

Description

protected Object

lock

The object used to synchronize operations on this stream.
Constructor Summary

Constructors

Constructor

Description

InputStreamReader(InputStream in)

Creates an InputStreamReader that uses the default charset.

InputStreamReader(InputStream in, String charsetName)

Creates an InputStreamReader that uses the named charset.

InputStreamReader(InputStream in, Charset cs)

Creates an InputStreamReader that uses the given charset.

InputStreamReader(InputStream in, CharsetDecoder dec)

Creates an InputStreamReader that uses the given charset decoder.
Method Summary

All MethodsInstance MethodsConcrete Methods

Modifier and Type

Method

Description

void

close()

Closes the stream and releases any system resources associated with it.

String

getEncoding()

Returns the name of the character encoding being used by this stream.

int

read()

Reads a single character.

int

read(char[] cbuf, int off, int len)

Reads characters into a portion of an array.

boolean

ready()

Tells whether this stream is ready to be read.

Methods declared in class Reader
mark, markSupported, nullReader, of, read, read, readAllAsString, readAllLines, reset, skip, transferTo

Modifier and Type

Method

Description

void

mark(int readAheadLimit)

Marks the present position in the stream.

boolean

markSupported()

Tells whether this stream supports the mark() operation.

static Reader

nullReader()

Returns a new Reader that reads no characters.

static Reader

of(CharSequence cs)

Returns a Reader that reads characters from a CharSequence.

int

read(char[] cbuf)

Reads characters into an array.

int

read(CharBuffer target)

Attempts to read characters into the specified character buffer.

String

readAllAsString()

Reads all remaining characters into a string.

List<String>

readAllLines()

Reads all remaining characters as lines of text.

void

reset()

Resets the stream.

long

skip(long n)

Skips characters.

long

transferTo(Writer out)

Reads all characters from this reader and writes the characters to the given writer in the order that they are read.

Methods declared in class Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Modifier and Type

Method

Description

protected Object

clone()

Creates and returns a copy of this object.

boolean

equals(Object obj)

Indicates whether some other object is "equal to" this one.

protected void

finalize()

Deprecated, for removal: This API element is subject to removal in a future version.
Finalization is deprecated and subject to removal in a future release.

final Class<?>

getClass()

Returns the runtime class of this Object.

int

hashCode()

Returns a hash code value for this object.

final void

notify()

Wakes up a single thread that is waiting on this object's monitor.

final void

notifyAll()

Wakes up all threads that are waiting on this object's monitor.

String

toString()

Returns a string representation of the object.

final void

wait()

Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

final void

wait(long timeoutMillis)

Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

final void

wait(long timeoutMillis, int nanos)

Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Constructor Details
- InputStreamReader
  public InputStreamReader(InputStream in)
  
  Creates an InputStreamReader that uses the default charset.
  Parameters: in - An InputStream See Also:
  - Charset.defaultCharset()
- InputStreamReader
  
  public InputStreamReader(InputStream in, String charsetName) throws UnsupportedEncodingException
  
  Creates an InputStreamReader that uses the named charset.
  Parameters: in - An InputStream charsetName - The name of a supported charset Throws: UnsupportedEncodingException - If the named charset is not supported
- InputStreamReader
  
  public InputStreamReader(InputStream in, Charset cs)
  
  Creates an InputStreamReader that uses the given charset.
  Parameters: in - An InputStream cs - A charset Since: 1.4
- InputStreamReader
  
  public InputStreamReader(InputStream in, CharsetDecoder dec)
  
  Creates an InputStreamReader that uses the given charset decoder.
  Parameters: in - An InputStream dec - A charset decoder Since: 1.4
Method Details
- getEncoding
  public String getEncoding()
  
  Returns the name of the character encoding being used by this stream.
  If the encoding has an historical name then that name is returned; otherwise the encoding's canonical name is returned.
  If this instance was created with the InputStreamReader(InputStream, String) constructor then the returned name, being unique for the encoding, may differ from the name passed to the constructor. This method will return null if the stream has been closed.
  Returns: The historical name of this encoding, or null if the stream has been closed See Also:
  - Charset
- read
  
  public int read() throws IOException
  
  Reads a single character.
  Overrides: read in class Reader Returns: The character read, or -1 if the end of the stream has been reached Throws: IOException - If an I/O error occurs
- read
  
  public int read(char[] cbuf, int off, int len) throws IOException
  
  Reads characters into a portion of an array. This method will block until some input is available, an I/O error occurs, or the end of the stream is reached.
  If len is zero, then no characters are read and 0 is returned; otherwise, there is an attempt to read at least one character. If no character is available because the stream is at its end, the value -1 is returned; otherwise, at least one character is read and stored into cbuf.
  Specified by: read in class Reader Parameters: cbuf - Destination buffer off - Offset at which to start storing characters len - Maximum number of characters to read Returns: The number of characters read, or -1 if the end of the stream has been reached Throws: IndexOutOfBoundsException - If off is negative, or len is negative, or len is greater than cbuf.length - off IOException - If an I/O error occurs
- ready
  
  public boolean ready() throws IOException
  
  Tells whether this stream is ready to be read. An InputStreamReader is ready if its input buffer is not empty, or if bytes are available to be read from the underlying byte stream.
  Overrides: ready in class Reader Returns: True if the next read() is guaranteed not to block for input, false otherwise. Note that returning false does not guarantee that the next read will block. Throws: IOException - If an I/O error occurs
- close
  
  public void close() throws IOException
  
  Description copied from class: Reader
  
  Closes the stream and releases any system resources associated with it. Once the stream has been closed, further read(), ready(), mark(), reset(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect.
  Specified by: close in interface AutoCloseable Specified by: close in interface Closeable Specified by: close in class Reader Throws: IOException - If an I/O error occurs

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For further API reference and developer documentation see the Java SE Documentation, which contains more detailed, developer-targeted descriptions with conceptual overviews, definitions of terms, workarounds, and working code examples. Other versions.
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Class InputStreamReader

Field Summary

Fields declared in class Reader

Constructor Summary

Method Summary

Methods declared in class Reader

Methods declared in class Object

Constructor Details

InputStreamReader

InputStreamReader

InputStreamReader

InputStreamReader

Method Details

getEncoding

read

read

ready

close