Module java.base
Package java.io

Class 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 platform's default character set.
      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).

    • Field Detail

      • buf

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

      • count

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

    • Constructor Detail

      • 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 Detail

      • 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:
        ByteArrayInputStream.count

      • 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()

      • 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:
        count

      • toString

        public String toString()
        Converts the buffer's contents into a string decoding bytes using the platform's default character set. The length of the new String is a function of the character set, 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 platform's default character set. 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

      • 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 platform's default character encoding.
        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:
        size(), toString(String), toString()

      • 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.