DataOutput interface provides
+ * for converting data from any of the Java
+ * primitive types to a series of bytes and
+ * writing these bytes to a binary stream.
+ * There is also a facility for converting
+ * a String into
+ * modified UTF-8
+ * format and writing the resulting series
+ * of bytes.
+ *
+ * For all the methods in this interface that
+ * write bytes, it is generally true that if
+ * a byte cannot be written for any reason,
+ * an IOException is thrown.
+ *
+ * @author Frank Yellin
+ * @see java.io.DataInput
+ * @see java.io.DataOutputStream
+ * @since JDK1.0
+ */
+public
+interface DataOutput {
+ /**
+ * Writes to the output stream the eight
+ * low-order bits of the argument b.
+ * The 24 high-order bits of b
+ * are ignored.
+ *
+ * @param b the byte to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void write(int b) throws IOException;
+
+ /**
+ * Writes to the output stream all the bytes in array b.
+ * If b is null,
+ * a NullPointerException is thrown.
+ * If b.length is zero, then
+ * no bytes are written. Otherwise, the byte
+ * b[0] is written first, then
+ * b[1], and so on; the last byte
+ * written is b[b.length-1].
+ *
+ * @param b the data.
+ * @throws IOException if an I/O error occurs.
+ */
+ void write(byte b[]) throws IOException;
+
+ /**
+ * Writes len bytes from array
+ * b, in order, to
+ * the output stream. If b
+ * is null, a NullPointerException
+ * is thrown. If off is negative,
+ * or len is negative, or off+len
+ * is greater than the length of the array
+ * b, then an IndexOutOfBoundsException
+ * is thrown. If len is zero,
+ * then no bytes are written. Otherwise, the
+ * byte b[off] is written first,
+ * then b[off+1], and so on; the
+ * last byte written is b[off+len-1].
+ *
+ * @param b the data.
+ * @param off the start offset in the data.
+ * @param len the number of bytes to write.
+ * @throws IOException if an I/O error occurs.
+ */
+ void write(byte b[], int off, int len) throws IOException;
+
+ /**
+ * Writes a boolean value to this output stream.
+ * If the argument v
+ * is true, the value (byte)1
+ * is written; if v is false,
+ * the value (byte)0 is written.
+ * The byte written by this method may
+ * be read by the readBoolean
+ * method of interface DataInput,
+ * which will then return a boolean
+ * equal to v.
+ *
+ * @param v the boolean to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeBoolean(boolean v) throws IOException;
+
+ /**
+ * Writes to the output stream the eight low-
+ * order bits of the argument v.
+ * The 24 high-order bits of v
+ * are ignored. (This means that writeByte
+ * does exactly the same thing as write
+ * for an integer argument.) The byte written
+ * by this method may be read by the readByte
+ * method of interface DataInput,
+ * which will then return a byte
+ * equal to (byte)v.
+ *
+ * @param v the byte value to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeByte(int v) throws IOException;
+
+ /**
+ * Writes two bytes to the output
+ * stream to represent the value of the argument.
+ * The byte values to be written, in the order
+ * shown, are:
+ *
+ * (byte)(0xff & (v >> 8))
+ * (byte)(0xff & v)
+ *
+ * The bytes written by this method may be
+ * read by the readShort method
+ * of interface DataInput , which
+ * will then return a short equal
+ * to (short)v.
+ *
+ * @param v the short value to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeShort(int v) throws IOException;
+
+ /**
+ * Writes a char value, which
+ * is comprised of two bytes, to the
+ * output stream.
+ * The byte values to be written, in the order
+ * shown, are:
+ *
+ * (byte)(0xff & (v >> 8))
+ * (byte)(0xff & v)
+ *
+ * The bytes written by this method may be
+ * read by the readChar method
+ * of interface DataInput , which
+ * will then return a char equal
+ * to (char)v.
+ *
+ * @param v the char value to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeChar(int v) throws IOException;
+
+ /**
+ * Writes an int value, which is
+ * comprised of four bytes, to the output stream.
+ * The byte values to be written, in the order
+ * shown, are:
+ *
+ * (byte)(0xff & (v >> 24))
+ * (byte)(0xff & (v >> 16))
+ * (byte)(0xff & (v >> 8))
+ * (byte)(0xff & v)
+ *
+ * The bytes written by this method may be read
+ * by the readInt method of interface
+ * DataInput , which will then
+ * return an int equal to v.
+ *
+ * @param v the int value to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeInt(int v) throws IOException;
+
+ /**
+ * Writes a long value, which is
+ * comprised of eight bytes, to the output stream.
+ * The byte values to be written, in the order
+ * shown, are:
+ *
+ * (byte)(0xff & (v >> 56))
+ * (byte)(0xff & (v >> 48))
+ * (byte)(0xff & (v >> 40))
+ * (byte)(0xff & (v >> 32))
+ * (byte)(0xff & (v >> 24))
+ * (byte)(0xff & (v >> 16))
+ * (byte)(0xff & (v >> 8))
+ * (byte)(0xff & v)
+ *
+ * The bytes written by this method may be
+ * read by the readLong method
+ * of interface DataInput , which
+ * will then return a long equal
+ * to v.
+ *
+ * @param v the long value to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeLong(long v) throws IOException;
+
+ /**
+ * Writes a float value,
+ * which is comprised of four bytes, to the output stream.
+ * It does this as if it first converts this
+ * float value to an int
+ * in exactly the manner of the Float.floatToIntBits
+ * method and then writes the int
+ * value in exactly the manner of the writeInt
+ * method. The bytes written by this method
+ * may be read by the readFloat
+ * method of interface DataInput,
+ * which will then return a float
+ * equal to v.
+ *
+ * @param v the float value to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeFloat(float v) throws IOException;
+
+ /**
+ * Writes a double value,
+ * which is comprised of eight bytes, to the output stream.
+ * It does this as if it first converts this
+ * double value to a long
+ * in exactly the manner of the Double.doubleToLongBits
+ * method and then writes the long
+ * value in exactly the manner of the writeLong
+ * method. The bytes written by this method
+ * may be read by the readDouble
+ * method of interface DataInput,
+ * which will then return a double
+ * equal to v.
+ *
+ * @param v the double value to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeDouble(double v) throws IOException;
+
+ /**
+ * Writes a string to the output stream.
+ * For every character in the string
+ * s, taken in order, one byte
+ * is written to the output stream. If
+ * s is null, a NullPointerException
+ * is thrown.
If s.length
+ * is zero, then no bytes are written. Otherwise,
+ * the character s[0] is written
+ * first, then s[1], and so on;
+ * the last character written is s[s.length-1].
+ * For each character, one byte is written,
+ * the low-order byte, in exactly the manner
+ * of the writeByte method . The
+ * high-order eight bits of each character
+ * in the string are ignored.
+ *
+ * @param s the string of bytes to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeBytes(String s) throws IOException;
+
+ /**
+ * Writes every character in the string s,
+ * to the output stream, in order,
+ * two bytes per character. If s
+ * is null, a NullPointerException
+ * is thrown. If s.length
+ * is zero, then no characters are written.
+ * Otherwise, the character s[0]
+ * is written first, then s[1],
+ * and so on; the last character written is
+ * s[s.length-1]. For each character,
+ * two bytes are actually written, high-order
+ * byte first, in exactly the manner of the
+ * writeChar method.
+ *
+ * @param s the string value to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeChars(String s) throws IOException;
+
+ /**
+ * Writes two bytes of length information
+ * to the output stream, followed
+ * by the
+ * modified UTF-8
+ * representation
+ * of every character in the string s.
+ * If s is null,
+ * a NullPointerException is thrown.
+ * Each character in the string s
+ * is converted to a group of one, two, or
+ * three bytes, depending on the value of the
+ * character.
+ * If a character c
+ * is in the range \u0001 through
+ * \u007f, it is represented
+ * by one byte:
+ *
(byte)c
+ * If a character c is \u0000
+ * or is in the range \u0080
+ * through \u07ff, then it is
+ * represented by two bytes, to be written
+ * in the order shown:
+ * (byte)(0xc0 | (0x1f & (c >> 6)))
+ * (byte)(0x80 | (0x3f & c))
+ * If a character
+ * c is in the range \u0800
+ * through uffff, then it is
+ * represented by three bytes, to be written
+ * in the order shown:
+ * (byte)(0xe0 | (0x0f & (c >> 12)))
+ * (byte)(0x80 | (0x3f & (c >> 6)))
+ * (byte)(0x80 | (0x3f & c))
+ * First,
+ * the total number of bytes needed to represent
+ * all the characters of s is
+ * calculated. If this number is larger than
+ * 65535, then a UTFDataFormatException
+ * is thrown. Otherwise, this length is written
+ * to the output stream in exactly the manner
+ * of the writeShort method;
+ * after this, the one-, two-, or three-byte
+ * representation of each character in the
+ * string s is written.
The
+ * bytes written by this method may be read
+ * by the readUTF method of interface
+ * DataInput , which will then
+ * return a String equal to s.
+ *
+ * @param s the string value to be written.
+ * @throws IOException if an I/O error occurs.
+ */
+ void writeUTF(String s) throws IOException;
+}