Module java.base
Package java.io

Class ByteArrayOutputStream

  • All Implemented Interfaces:
    Closeable,Flushable,AutoCloseable
    public classByteArrayOutputStreamextendsOutputStream
    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 usingtoByteArray() andtoString().

    Closing aByteArrayOutputStream has no effect. The methods in this class can be called after the stream has been closed without generating anIOException.

    Since:
    1.0

    • Field Summary

      Fields 
      Modifier and TypeFieldDescription
      protected byte[]buf
      The buffer where data is stored.
      protected intcount
      The number of valid bytes in the buffer.

    • Constructor Summary

      Constructors 
      ConstructorDescription
      ByteArrayOutputStream()
      Creates a newByteArrayOutputStream.
      ByteArrayOutputStream​(int size)
      Creates a newByteArrayOutputStream, with a buffer capacity of the specified size, in bytes.

    • Method Summary

      All Methods Instance Methods Concrete Methods Deprecated Methods 
      Modifier and TypeMethodDescription
      voidclose()
      Closing aByteArrayOutputStream has no effect.
      voidreset()
      Resets thecount field of thisByteArrayOutputStream to zero, so that all currently accumulated output in the output stream is discarded.
      intsize()
      Returns the current size of the buffer.
      byte[]toByteArray()
      Creates a newly allocated byte array.
      StringtoString()
      Converts the buffer's contents into a string decoding bytes using the platform's default character set.
      StringtoString​(int hibyte)
      Deprecated.
      This method does not properly convert bytes into characters.
      StringtoString​(String charsetName)
      Converts the buffer's contents into a string by decoding the bytes using the namedcharset.
      StringtoString​(Charset charset)
      Converts the buffer's contents into a string by decoding the bytes using the specifiedcharset.
      voidwrite​(byte[] b, int off, int len)
      Writeslen bytes from the specified byte array starting at offsetoff to thisByteArrayOutputStream.
      voidwrite​(int b)
      Writes the specified byte to thisByteArrayOutputStream.
      voidwriteBytes​(byte[] b)
      Writes the complete contents of the specified byte array to thisByteArrayOutputStream.
      voidwriteTo​(OutputStream out)
      Writes the complete contents of thisByteArrayOutputStream to the specified output stream argument, as if by calling the output stream's write method usingout.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 newByteArrayOutputStream. The buffer capacity is initially 32 bytes, though its size increases if necessary.

      • ByteArrayOutputStream

        public ByteArrayOutputStream​(int size)
        Creates a newByteArrayOutputStream, 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 thisByteArrayOutputStream.
        Specified by:
        write in class OutputStream
        Parameters:
        b - the byte to be written.

      • write

        public void write​(byte[] b,                  int off,                  int len)
        Writeslen bytes from the specified byte array starting at offsetoff to thisByteArrayOutputStream.
        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 - ifb isnull.
        IndexOutOfBoundsException - ifoff is negative,len is negative, orlen is greater thanb.length - off

      • writeBytes

        public void writeBytes​(byte[] b)
        Writes the complete contents of the specified byte array to thisByteArrayOutputStream.
        API Note:
        This method is equivalent towrite(b, 0, b.length).
        Parameters:
        b - the data.
        Throws:
        NullPointerException - ifb isnull.
        Since:
        11

      • writeTo

        public void writeTo​(OutputStream out)             throwsIOException
        Writes the complete contents of thisByteArrayOutputStream to the specified output stream argument, as if by calling the output stream's write method usingout.write(buf, 0, count).
        Parameters:
        out - the output stream to which to write the data.
        Throws:
        NullPointerException - ifout isnull.
        IOException - if an I/O error occurs.

      • reset

        public void reset()
        Resets thecount field of thisByteArrayOutputStream 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 thecount 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 newString 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. TheCharsetDecoder 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)                throwsUnsupportedEncodingException
        Converts the buffer's contents into a string by decoding the bytes using the namedcharset.

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

        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 supportedcharset
        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 specifiedcharset. The length of the newString 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. TheCharsetDecoder class should be used when more control over the decoding process is required.

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

      • toString

        @Deprecatedpublic 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 thetoString(String charsetName) ortoString(Charset charset) method, which takes an encoding-name or charset argument, or thetoString() 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 characterc in the resulting string is constructed from the corresponding elementb 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()           throwsIOException
        Closing aByteArrayOutputStream has no effect. The methods in this class can be called after the stream has been closed without generating anIOException.
        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.