The DataOutputStream class allows applications to write primitive Java data types in a portable way to an output stream. It extends the OutputStream class and implements the DataOutput interface. A DataOutputStream is constructed by passing an OutputStream, and can then be used to write data types like strings, booleans, and integers to the underlying stream using methods like writeUTF(), writeBoolean(), and writeInt(). It also contains methods like flush() and close() to flush or close the stream.

1. Class DataOutputStream
DataOutputStream

2. DataOutputStream
• 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.
DataOutputStream

3. java.io.DataOutputStream
public class DataOutputStream extends OutputStream
implements DataOutput
DataOutputStream

4. DataOutputStream constructor
• DataOutputStream(OutputStream out)
• Creates a new data output stream to write
data to the specified underlying output
stream.
DataOutputStream

5. writeUTF()
• Writes a string to the underlying output
stream using UTF-8 encoding in a machineindependent manner.
DataOutputStream

6. writeUTF()
• public final void writeUTF(String str) throws
IOException
• 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 UTF-8
encoding for the character.
DataOutputStream

7. writeBoolean()
• 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.
DataOutputStream

8. writeBoolean()
syntax
public final void writeBoolean(boolean v)
throws IOException
DataOutputStream

9. writeInt()
• Writes an int to the underlying output stream
as four bytes, high byte first
• public final void writeInt(int v) throws
IOException
DataOutputStream

10. Flush()
• 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.
• public void flush() throws IOException
DataOutputStream

11. Close()
• Closes this output stream and releases any
system resources associated with the
stream.The close method calls
its flush method, and then calls
the close method of its underlying output
stream.
• public void close() throws IOException
DataOutputStream