This class is a subclass of FilterOutputStream that allows you to write Java primitive data types in a portable binary format. Create a DataOutputStream by specifying the OutputStream that is to be filtered in the call to the constructor. DataOutputStream has methods that output only primitive types; use ObjectOutputStream to output object values.

Many of this class's methods write a single Java primitive type, in binary format, to the output stream. write( ) writes a single byte, an array, or a subarray of bytes. flush( ) forces any buffered data to be output. size( ) returns the number of bytes written so far. writeUTF( ) outputs a Java string of Unicode characters using a slightly modified version of the UTF-8 transformation format. UTF-8 is an ASCII-compatible encoding of Unicode characters that is often used for the transmission and storage of Unicode text. Except for the writeUTF( ) method, this class is used for binary output of data. Textual output should be done with PrintWriter (or PrintStream in Java 1.0).

Figure 9-11. java.io.DataOutputStream

public class DataOutputStream extends FilterOutputStream implements DataOutput {
// Public Constructors
     public DataOutputStream(OutputStream out);  
// Public Instance Methods
     public final int size( );  
// Methods Implementing DataOutput
     public void write(int b) throws IOException;                 synchronized
     public void write(byte[ ] b, int off, int len) throws IOException;     synchronized
     public final void writeBoolean(boolean v) throws IOException;  
     public final void writeByte(int v) throws IOException;  
     public final void writeBytes(String s) throws IOException;  
     public final void writeChar(int v) throws IOException;  
     public final void writeChars(String s) throws IOException;  
     public final void writeDouble(double v) throws IOException;  
     public final void writeFloat(float v) throws IOException;  
     public final void writeInt(int v) throws IOException;  
     public final void writeLong(long v) throws IOException;  
     public final void writeShort(int v) throws IOException;  
     public final void writeUTF(String str) throws IOException;  
// Public Methods Overriding FilterOutputStream
     public void flush( ) throws IOException;  
// Protected Instance Fields
     protected int written;  
}