Java tutorial
/* * Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.io; /** * The <code>DataOutput</code> 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 <code>String</code> into * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> * format and writing the resulting series * of bytes. * <p> * 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 <code>IOException</code> is thrown. * * @author Frank Yellin * @see java.io.DataInput * @see java.io.DataOutputStream * @since 1.0 */ public interface DataOutput { /** * Writes to the output stream the eight * low-order bits of the argument <code>b</code>. * The 24 high-order bits of <code>b</code> * 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 <code>b</code>. * If <code>b</code> is <code>null</code>, * a <code>NullPointerException</code> is thrown. * If <code>b.length</code> is zero, then * no bytes are written. Otherwise, the byte * <code>b[0]</code> is written first, then * <code>b[1]</code>, and so on; the last byte * written is <code>b[b.length-1]</code>. * * @param b the data. * @throws IOException if an I/O error occurs. */ void write(byte b[]) throws IOException; /** * Writes <code>len</code> bytes from array * <code>b</code>, in order, to * the output stream. If <code>b</code> * is <code>null</code>, a <code>NullPointerException</code> * is thrown. If <code>off</code> is negative, * or <code>len</code> is negative, or <code>off+len</code> * is greater than the length of the array * <code>b</code>, then an <code>IndexOutOfBoundsException</code> * is thrown. If <code>len</code> is zero, * then no bytes are written. Otherwise, the * byte <code>b[off]</code> is written first, * then <code>b[off+1]</code>, and so on; the * last byte written is <code>b[off+len-1]</code>. * * @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 <code>boolean</code> value to this output stream. * If the argument <code>v</code> * is <code>true</code>, the value <code>(byte)1</code> * is written; if <code>v</code> is <code>false</code>, * the value <code>(byte)0</code> is written. * The byte written by this method may * be read by the <code>readBoolean</code> * method of interface <code>DataInput</code>, * which will then return a <code>boolean</code> * equal to <code>v</code>. * * @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 <code>v</code>. * The 24 high-order bits of <code>v</code> * are ignored. (This means that <code>writeByte</code> * does exactly the same thing as <code>write</code> * for an integer argument.) The byte written * by this method may be read by the <code>readByte</code> * method of interface <code>DataInput</code>, * which will then return a <code>byte</code> * equal to <code>(byte)v</code>. * * @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: * <pre>{@code * (byte)(0xff & (v >> 8)) * (byte)(0xff & v) * }</pre> <p> * The bytes written by this method may be * read by the <code>readShort</code> method * of interface <code>DataInput</code> , which * will then return a <code>short</code> equal * to <code>(short)v</code>. * * @param v the <code>short</code> value to be written. * @throws IOException if an I/O error occurs. */ void writeShort(int v) throws IOException; /** * Writes a <code>char</code> value, which * is comprised of two bytes, to the * output stream. * The byte values to be written, in the order * shown, are: * <pre>{@code * (byte)(0xff & (v >> 8)) * (byte)(0xff & v) * }</pre><p> * The bytes written by this method may be * read by the <code>readChar</code> method * of interface <code>DataInput</code> , which * will then return a <code>char</code> equal * to <code>(char)v</code>. * * @param v the <code>char</code> value to be written. * @throws IOException if an I/O error occurs. */ void writeChar(int v) throws IOException; /** * Writes an <code>int</code> value, which is * comprised of four bytes, to the output stream. * The byte values to be written, in the order * shown, are: * <pre>{@code * (byte)(0xff & (v >> 24)) * (byte)(0xff & (v >> 16)) * (byte)(0xff & (v >> 8)) * (byte)(0xff & v) * }</pre><p> * The bytes written by this method may be read * by the <code>readInt</code> method of interface * <code>DataInput</code> , which will then * return an <code>int</code> equal to <code>v</code>. * * @param v the <code>int</code> value to be written. * @throws IOException if an I/O error occurs. */ void writeInt(int v) throws IOException; /** * Writes a <code>long</code> value, which is * comprised of eight bytes, to the output stream. * The byte values to be written, in the order * shown, are: * <pre>{@code * (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) * }</pre><p> * The bytes written by this method may be * read by the <code>readLong</code> method * of interface <code>DataInput</code> , which * will then return a <code>long</code> equal * to <code>v</code>. * * @param v the <code>long</code> value to be written. * @throws IOException if an I/O error occurs. */ void writeLong(long v) throws IOException; /** * Writes a <code>float</code> value, * which is comprised of four bytes, to the output stream. * It does this as if it first converts this * <code>float</code> value to an <code>int</code> * in exactly the manner of the <code>Float.floatToIntBits</code> * method and then writes the <code>int</code> * value in exactly the manner of the <code>writeInt</code> * method. The bytes written by this method * may be read by the <code>readFloat</code> * method of interface <code>DataInput</code>, * which will then return a <code>float</code> * equal to <code>v</code>. * * @param v the <code>float</code> value to be written. * @throws IOException if an I/O error occurs. */ void writeFloat(float v) throws IOException; /** * Writes a <code>double</code> value, * which is comprised of eight bytes, to the output stream. * It does this as if it first converts this * <code>double</code> value to a <code>long</code> * in exactly the manner of the <code>Double.doubleToLongBits</code> * method and then writes the <code>long</code> * value in exactly the manner of the <code>writeLong</code> * method. The bytes written by this method * may be read by the <code>readDouble</code> * method of interface <code>DataInput</code>, * which will then return a <code>double</code> * equal to <code>v</code>. * * @param v the <code>double</code> 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 * <code>s</code>, taken in order, one byte * is written to the output stream. If * <code>s</code> is <code>null</code>, a <code>NullPointerException</code> * is thrown.<p> If <code>s.length</code> * is zero, then no bytes are written. Otherwise, * the character <code>s[0]</code> is written * first, then <code>s[1]</code>, and so on; * the last character written is <code>s[s.length-1]</code>. * For each character, one byte is written, * the low-order byte, in exactly the manner * of the <code>writeByte</code> 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 <code>s</code>, * to the output stream, in order, * two bytes per character. If <code>s</code> * is <code>null</code>, a <code>NullPointerException</code> * is thrown. If <code>s.length</code> * is zero, then no characters are written. * Otherwise, the character <code>s[0]</code> * is written first, then <code>s[1]</code>, * and so on; the last character written is * <code>s[s.length-1]</code>. For each character, * two bytes are actually written, high-order * byte first, in exactly the manner of the * <code>writeChar</code> 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 * <a href="DataInput.html#modified-utf-8">modified UTF-8</a> * representation * of every character in the string <code>s</code>. * If <code>s</code> is <code>null</code>, * a <code>NullPointerException</code> is thrown. * Each character in the string <code>s</code> * is converted to a group of one, two, or * three bytes, depending on the value of the * character.<p> * If a character <code>c</code> * is in the range <code>\u0001</code> through * <code>\u007f</code>, it is represented * by one byte: * <pre>(byte)c </pre> <p> * If a character <code>c</code> is <code>\u0000</code> * or is in the range <code>\u0080</code> * through <code>\u07ff</code>, then it is * represented by two bytes, to be written * in the order shown: <pre>{@code * (byte)(0xc0 | (0x1f & (c >> 6))) * (byte)(0x80 | (0x3f & c)) * }</pre> <p> If a character * <code>c</code> is in the range <code>\u0800</code> * through <code>uffff</code>, then it is * represented by three bytes, to be written * in the order shown: <pre>{@code * (byte)(0xe0 | (0x0f & (c >> 12))) * (byte)(0x80 | (0x3f & (c >> 6))) * (byte)(0x80 | (0x3f & c)) * }</pre> <p> First, * the total number of bytes needed to represent * all the characters of <code>s</code> is * calculated. If this number is larger than * <code>65535</code>, then a <code>UTFDataFormatException</code> * is thrown. Otherwise, this length is written * to the output stream in exactly the manner * of the <code>writeShort</code> method; * after this, the one-, two-, or three-byte * representation of each character in the * string <code>s</code> is written.<p> The * bytes written by this method may be read * by the <code>readUTF</code> method of interface * <code>DataInput</code> , which will then * return a <code>String</code> equal to <code>s</code>. * * @param s the string value to be written. * @throws IOException if an I/O error occurs. */ void writeUTF(String s) throws IOException; }