Module java.base
Package java.io

Class DataOutputStream

All Implemented Interfaces:
Closeable, DataOutput, Flushable, AutoCloseable

public class DataOutputStream extends FilterOutputStream implements DataOutput
A data output stream lets an application write primitive Java data types to an output stream in a portable way. An application can then use a data input stream to read the data back in.

A DataOutputStream is not safe for use by multiple concurrent threads. If a DataOutputStream is to be used by more than one thread then access to the data output stream should be controlled by appropriate synchronization.

Since:
1.0
See Also:
DataInputStream
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected int
    The number of bytes written to the data output stream so far.

    Fields declared in class java.io.FilterOutputStream

    out
  • Constructor Summary

    Constructors
    Constructor
    Description
    Creates a new data output stream to write data to the specified underlying output stream.
  • Method Summary

    Modifier and Type
    Method
    Description
    void
    Flushes this data output stream.
    final int
    Returns the current value of the counter written, the number of bytes written to this data output stream so far.
    void
    write​(byte[] b, int off, int len)
    Writes len bytes from the specified byte array starting at offset off to the underlying output stream.
    void
    write​(int b)
    Writes the specified byte (the low eight bits of the argument b) to the underlying output stream.
    final void
    writeBoolean​(boolean v)
    Writes a boolean to the underlying output stream as a 1-byte value.
    final void
    writeByte​(int v)
    Writes out a byte to the underlying output stream as a 1-byte value.
    final void
    Writes out the string to the underlying output stream as a sequence of bytes.
    final void
    writeChar​(int v)
    Writes a char to the underlying output stream as a 2-byte value, high byte first.
    final void
    Writes a string to the underlying output stream as a sequence of characters.
    final void
    writeDouble​(double v)
    Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the underlying output stream as an 8-byte quantity, high byte first.
    final void
    writeFloat​(float v)
    Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the underlying output stream as a 4-byte quantity, high byte first.
    final void
    writeInt​(int v)
    Writes an int to the underlying output stream as four bytes, high byte first.
    final void
    writeLong​(long v)
    Writes a long to the underlying output stream as eight bytes, high byte first.
    final void
    writeShort​(int v)
    Writes a short to the underlying output stream as two bytes, high byte first.
    final void
    writeUTF​(String str)
    Writes a string to the underlying output stream using modified UTF-8 encoding in a machine-independent manner.

    Methods declared in class java.io.FilterOutputStream

    close, write

    Methods declared in class java.io.OutputStream

    nullOutputStream

    Methods declared in class java.lang.Object

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

    Methods declared in interface java.io.DataOutput

    write
  • Field Details

    • written

      protected int written
      The number of bytes written to the data output stream so far. If this counter overflows, it will be wrapped to Integer.MAX_VALUE.
  • Constructor Details

    • DataOutputStream

      public DataOutputStream(OutputStream out)
      Creates a new data output stream to write data to the specified underlying output stream. The counter written is set to zero.
      Parameters:
      out - the underlying output stream, to be saved for later use.
      See Also:
      FilterOutputStream.out
  • Method Details

    • write

      public void write(int b) throws IOException
      Writes the specified byte (the low eight bits of the argument b) to the underlying output stream. If no exception is thrown, the counter written is incremented by 1.

      Implements the write method of OutputStream.

      Specified by:
      write in interface DataOutput
      Overrides:
      write in class FilterOutputStream
      Parameters:
      b - the byte to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out
    • write

      public void write(byte[] b, int off, int len) throws IOException
      Writes len bytes from the specified byte array starting at offset off to the underlying output stream. If no exception is thrown, the counter written is incremented by len.
      Specified by:
      write in interface DataOutput
      Overrides:
      write in class FilterOutputStream
      Parameters:
      b - the data.
      off - the start offset in the data.
      len - the number of bytes to write.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out
    • flush

      public void flush() throws IOException
      Flushes this data output stream. This forces any buffered output bytes to be written out to the stream.

      The flush method of DataOutputStream calls the flush method of its underlying output stream.

      Specified by:
      flush in interface Flushable
      Overrides:
      flush in class FilterOutputStream
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out, OutputStream.flush()
    • writeBoolean

      public final void writeBoolean(boolean v) throws IOException
      Writes a boolean to the underlying output stream as a 1-byte value. The value true is written out as the value (byte)1; the value false is written out as the value (byte)0. If no exception is thrown, the counter written is incremented by 1.
      Specified by:
      writeBoolean in interface DataOutput
      Parameters:
      v - a boolean value to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out
    • writeByte

      public final void writeByte(int v) throws IOException
      Writes out a byte to the underlying output stream as a 1-byte value. If no exception is thrown, the counter written is incremented by 1.
      Specified by:
      writeByte in interface DataOutput
      Parameters:
      v - a byte value to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out
    • writeShort

      public final void writeShort(int v) throws IOException
      Writes a short to the underlying output stream as two bytes, high byte first. If no exception is thrown, the counter written is incremented by 2.
      Specified by:
      writeShort in interface DataOutput
      Parameters:
      v - a short to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out
    • writeChar

      public final void writeChar(int v) throws IOException
      Writes a char to the underlying output stream as a 2-byte value, high byte first. If no exception is thrown, the counter written is incremented by 2.
      Specified by:
      writeChar in interface DataOutput
      Parameters:
      v - a char value to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out
    • writeInt

      public final void writeInt(int v) throws IOException
      Writes an int to the underlying output stream as four bytes, high byte first. If no exception is thrown, the counter written is incremented by 4.
      Specified by:
      writeInt in interface DataOutput
      Parameters:
      v - an int to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out
    • writeLong

      public final void writeLong(long v) throws IOException
      Writes a long to the underlying output stream as eight bytes, high byte first. In no exception is thrown, the counter written is incremented by 8.
      Specified by:
      writeLong in interface DataOutput
      Parameters:
      v - a long to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out
    • writeFloat

      public final void writeFloat(float v) throws IOException
      Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the underlying output stream as a 4-byte quantity, high byte first. If no exception is thrown, the counter written is incremented by 4.
      Specified by:
      writeFloat in interface DataOutput
      Parameters:
      v - a float value to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out, Float.floatToIntBits(float)
    • writeDouble

      public final void writeDouble(double v) throws IOException
      Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the underlying output stream as an 8-byte quantity, high byte first. If no exception is thrown, the counter written is incremented by 8.
      Specified by:
      writeDouble in interface DataOutput
      Parameters:
      v - a double value to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out, Double.doubleToLongBits(double)
    • writeBytes

      public final void writeBytes(String s) throws IOException
      Writes out the string to the underlying output stream as a sequence of bytes. Each character in the string is written out, in sequence, by discarding its high eight bits. If no exception is thrown, the counter written is incremented by the length of s.
      Specified by:
      writeBytes in interface DataOutput
      Parameters:
      s - a string of bytes to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      FilterOutputStream.out
    • writeChars

      public final void writeChars(String s) throws IOException
      Writes a string to the underlying output stream as a sequence of characters. Each character is written to the data output stream as if by the writeChar method. If no exception is thrown, the counter written is incremented by twice the length of s.
      Specified by:
      writeChars in interface DataOutput
      Parameters:
      s - a String value to be written.
      Throws:
      IOException - if an I/O error occurs.
      See Also:
      writeChar(int), FilterOutputStream.out
    • writeUTF

      public final void writeUTF(String str) throws IOException
      Writes a string to the underlying output stream using modified UTF-8 encoding in a machine-independent manner.

      First, two bytes are written to the output stream as if by the writeShort method giving the number of bytes to follow. This value is the number of bytes actually written out, not the length of the string. Following the length, each character of the string is output, in sequence, using the modified UTF-8 encoding for the character. If no exception is thrown, the counter written is incremented by the total number of bytes written to the output stream. This will be at least two plus the length of str, and at most two plus thrice the length of str.

      Specified by:
      writeUTF in interface DataOutput
      Parameters:
      str - a string to be written.
      Throws:
      UTFDataFormatException - if the modified UTF-8 encoding of str would exceed 65535 bytes in length
      IOException - if some other I/O error occurs.
      See Also:
      writeChars(String)
    • size

      public final int size()
      Returns the current value of the counter written, the number of bytes written to this data output stream so far. If the counter overflows, it will be wrapped to Integer.MAX_VALUE.
      Returns:
      the value of the written field.
      See Also:
      written