This class is a byte output stream with an associated MessageDigest object. When bytes are written to the stream with any of the write( ) methods, those bytes are automatically passed to the update( ) method of the MessageDigest. When you have finished writing bytes, you can call the digest( ) method of the MessageDigest to obtain a message digest. If you want to compute a digest just for some of the bytes written to the stream, use on( ) to turn the digesting function on and off. Digesting is on by default; call on(false) to turn it off. See also DigestInputStream and MessageDigest.

Figure 14-9. java.security.DigestOutputStream

public class DigestOutputStream extends java.io.FilterOutputStream {
// Public Constructors
     public DigestOutputStream(java.io.OutputStream stream, 
        MessageDigest digest);  
// Public Instance Methods
     public MessageDigest getMessageDigest( );  
     public void on(boolean on);  
     public void setMessageDigest(MessageDigest digest);  
// Public Methods Overriding FilterOutputStream
     public void write(int b) throws java.io.IOException;  
     public void write(byte[ ] b, int off, int len) throws java.io.IOException;
// Public Methods Overriding Object
     public String toString( );  
// Protected Instance Fields
     protected MessageDigest digest;  
}