Module java.base
Package java.io

Class ByteArrayOutputStream

java.lang.Object
java.io.OutputStream
java.io.ByteArrayOutputStream
All Implemented Interfaces:
Closeable, Flushable, AutoCloseable
public class ByteArrayOutputStream extends OutputStream
This class implements an output stream in which the data is written into a byte array. The buffer automatically grows as data is written to it. The data can be retrieved using toByteArray() and toString().

Closing a ByteArrayOutputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException.

Since:
1.0

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected byte[]
    buf
    The buffer where data is stored.
    protected int
    count
    The number of valid bytes in the buffer.

  • Constructor Summary

    Constructors
    Constructor
    Description
    ByteArrayOutputStream()
    Creates a new ByteArrayOutputStream.
    ByteArrayOutputStream(int size)
    Creates a new ByteArrayOutputStream, with a buffer capacity of the specified size, in bytes.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    close()
    Closing a ByteArrayOutputStream has no effect.
    void
    reset()
    Resets the count field of this ByteArrayOutputStream to zero, so that all currently accumulated output in the output stream is discarded.
    int
    size()
    Returns the current size of the buffer.
    byte[]
    toByteArray()
    Creates a newly allocated byte array.
    String
    toString()
    Converts the buffer's contents into a string decoding bytes using the default charset.
    String
    toString(int hibyte)
    Deprecated.
    This method does not properly convert bytes into characters.
    String
    toString(String charsetName)
    Converts the buffer's contents into a string by decoding the bytes using the named charset.
    String
    toString(Charset charset)
    Converts the buffer's contents into a string by decoding the bytes using the specified charset.
    void
    write(byte[] b, int off, int len)
    Writes len bytes from the specified byte array starting at offset off to this ByteArrayOutputStream.
    void
    write(int b)
    Writes the specified byte to this ByteArrayOutputStream.
    void
    writeBytes(byte[] b)
    Writes the complete contents of the specified byte array to this ByteArrayOutputStream.
    void
    writeTo(OutputStream out)
    Writes the complete contents of this ByteArrayOutputStream to the specified output stream argument, as if by calling the output stream's write method using out.write(buf, 0, count).

    Methods declared in class java.io.OutputStream

    flush, nullOutputStream, write

    Methods declared in class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

  • Field Details

    • buf

      protected byte[] buf
      The buffer where data is stored.

    • count

      protected int count
      The number of valid bytes in the buffer.

  • Constructor Details

    • ByteArrayOutputStream

      public ByteArrayOutputStream()
      Creates a new ByteArrayOutputStream. The buffer capacity is initially 32 bytes, though its size increases if necessary.

    • ByteArrayOutputStream

      public ByteArrayOutputStream(int size)
      Creates a new ByteArrayOutputStream, with a buffer capacity of the specified size, in bytes.
      Parameters:
      size - the initial size.
      Throws:
      IllegalArgumentException - if size is negative.

  • Method Details

    • write

      public void write(int b)
      Writes the specified byte to this ByteArrayOutputStream.
      Specified by:
      write in class OutputStream
      Parameters:
      b - the byte to be written.

    • write

      public void write(byte[] b, int off, int len)
      Writes len bytes from the specified byte array starting at offset off to this ByteArrayOutputStream.
      Overrides:
      write in class OutputStream
      Parameters:
      b - the data.
      off - the start offset in the data.
      len - the number of bytes to write.
      Throws:
      NullPointerException - if b is null.
      IndexOutOfBoundsException - if off is negative, len is negative, or len is greater than b.length - off

    • writeBytes

      public void writeBytes(byte[] b)
      Writes the complete contents of the specified byte array to this ByteArrayOutputStream.
      API Note:
      This method is equivalent to write(b, 0, b.length).
      Parameters:
      b - the data.
      Throws:
      NullPointerException - if b is null.
      Since:
      11

    • writeTo

      public void writeTo(OutputStream out) throws IOException
      Writes the complete contents of this ByteArrayOutputStream to the specified output stream argument, as if by calling the output stream's write method using out.write(buf, 0, count).
      Parameters:
      out - the output stream to which to write the data.
      Throws:
      NullPointerException - if out is null.
      IOException - if an I/O error occurs.

    • reset

      public void reset()
      Resets the count field of this ByteArrayOutputStream to zero, so that all currently accumulated output in the output stream is discarded. The output stream can be used again, reusing the already allocated buffer space.
      See Also:

    • toByteArray

      public byte[] toByteArray()
      Creates a newly allocated byte array. Its size is the current size of this output stream and the valid contents of the buffer have been copied into it.
      Returns:
      the current contents of this output stream, as a byte array.
      See Also:

    • size

      public int size()
      Returns the current size of the buffer.
      Returns:
      the value of the count field, which is the number of valid bytes in this output stream.
      See Also:

    • toString

      public String toString()
      Converts the buffer's contents into a string decoding bytes using the default charset. The length of the new String is a function of the charset, and hence may not be equal to the size of the buffer.

      This method always replaces malformed-input and unmappable-character sequences with the default replacement string for the default charset. The CharsetDecoder class should be used when more control over the decoding process is required.

      Overrides:
      toString in class Object
      Returns:
      String decoded from the buffer's contents.
      Since:
      1.1
      See Also:

    • toString

      public String toString(String charsetName) throws UnsupportedEncodingException
      Converts the buffer's contents into a string by decoding the bytes using the named charset.

      This method is equivalent to #toString(charset) that takes a charset.

      An invocation of this method of the form 

          ByteArrayOutputStream b;
    b.toString("UTF-8")
      behaves in exactly the same way as the expression 
          ByteArrayOutputStream b;
    b.toString(StandardCharsets.UTF_8)
      Parameters:
      charsetName - the name of a supported charset
      Returns:
      String decoded from the buffer's contents.
      Throws:
      UnsupportedEncodingException - If the named charset is not supported
      Since:
      1.1

    • toString

      public String toString(Charset charset)
      Converts the buffer's contents into a string by decoding the bytes using the specified charset. The length of the new String is a function of the charset, and hence may not be equal to the length of the byte array.

      This method always replaces malformed-input and unmappable-character sequences with the charset's default replacement string. The CharsetDecoder class should be used when more control over the decoding process is required.

      Parameters:
      charset - the charset to be used to decode the bytes
      Returns:
      String decoded from the buffer's contents.
      Since:
      10

    • toString

      @Deprecated public String toString(int hibyte)
      Deprecated.
      This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the toString(String charsetName) or toString(Charset charset) method, which takes an encoding-name or charset argument, or the toString() method, which uses the default charset.
      Creates a newly allocated string. Its size is the current size of the output stream and the valid contents of the buffer have been copied into it. Each character c in the resulting string is constructed from the corresponding element b in the byte array such that: 
          c == (char)(((hibyte & 0xff) << 8) | (b & 0xff))
      Parameters:
      hibyte - the high byte of each resulting Unicode character.
      Returns:
      the current contents of the output stream, as a string.
      See Also:

    • close

      public void close() throws IOException
      Closing a ByteArrayOutputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class OutputStream
      Throws:
      IOException - if an I/O error occurs.