Java tutorial
/* * Copyright (c) 1996, 2016, 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; import java.util.Arrays; /** * This class implements a character buffer that can be used as an Writer. * The buffer automatically grows when data is written to the stream. The data * can be retrieved using toCharArray() and toString(). * <P> * Note: Invoking close() on this class has no effect, and methods * of this class can be called after the stream has closed * without generating an IOException. * * @author Herb Jellinek * @since 1.1 */ public class CharArrayWriter extends Writer { /** * The buffer where data is stored. */ protected char buf[]; /** * The number of chars in the buffer. */ protected int count; /** * Creates a new CharArrayWriter. */ public CharArrayWriter() { this(32); } /** * Creates a new CharArrayWriter with the specified initial size. * * @param initialSize an int specifying the initial buffer size. * @exception IllegalArgumentException if initialSize is negative */ public CharArrayWriter(int initialSize) { if (initialSize < 0) { throw new IllegalArgumentException("Negative initial size: " + initialSize); } buf = new char[initialSize]; } /** * Writes a character to the buffer. */ public void write(int c) { synchronized (lock) { int newcount = count + 1; if (newcount > buf.length) { buf = Arrays.copyOf(buf, Math.max(buf.length << 1, newcount)); } buf[count] = (char) c; count = newcount; } } /** * Writes characters to the buffer. * @param c the data to be written * @param off the start offset in the data * @param len the number of chars that are written * * @throws IndexOutOfBoundsException * If {@code off} is negative, or {@code len} is negative, * or {@code off + len} is negative or greater than the length * of the given array */ public void write(char c[], int off, int len) { if ((off < 0) || (off > c.length) || (len < 0) || ((off + len) > c.length) || ((off + len) < 0)) { throw new IndexOutOfBoundsException(); } else if (len == 0) { return; } synchronized (lock) { int newcount = count + len; if (newcount > buf.length) { buf = Arrays.copyOf(buf, Math.max(buf.length << 1, newcount)); } System.arraycopy(c, off, buf, count, len); count = newcount; } } /** * Write a portion of a string to the buffer. * @param str String to be written from * @param off Offset from which to start reading characters * @param len Number of characters to be written * * @throws IndexOutOfBoundsException * If {@code off} is negative, or {@code len} is negative, * or {@code off + len} is negative or greater than the length * of the given string */ public void write(String str, int off, int len) { synchronized (lock) { int newcount = count + len; if (newcount > buf.length) { buf = Arrays.copyOf(buf, Math.max(buf.length << 1, newcount)); } str.getChars(off, off + len, buf, count); count = newcount; } } /** * Writes the contents of the buffer to another character stream. * * @param out the output stream to write to * @throws IOException If an I/O error occurs. */ public void writeTo(Writer out) throws IOException { synchronized (lock) { out.write(buf, 0, count); } } /** * Appends the specified character sequence to this writer. * * <p> An invocation of this method of the form {@code out.append(csq)} * behaves in exactly the same way as the invocation * * <pre> * out.write(csq.toString()) </pre> * * <p> Depending on the specification of {@code toString} for the * character sequence {@code csq}, the entire sequence may not be * appended. For instance, invoking the {@code toString} method of a * character buffer will return a subsequence whose content depends upon * the buffer's position and limit. * * @param csq * The character sequence to append. If {@code csq} is * {@code null}, then the four characters {@code "null"} are * appended to this writer. * * @return This writer * * @since 1.5 */ public CharArrayWriter append(CharSequence csq) { String s = String.valueOf(csq); write(s, 0, s.length()); return this; } /** * Appends a subsequence of the specified character sequence to this writer. * * <p> An invocation of this method of the form * {@code out.append(csq, start, end)} when * {@code csq} is not {@code null}, behaves in * exactly the same way as the invocation * * <pre> * out.write(csq.subSequence(start, end).toString()) </pre> * * @param csq * The character sequence from which a subsequence will be * appended. If {@code csq} is {@code null}, then characters * will be appended as if {@code csq} contained the four * characters {@code "null"}. * * @param start * The index of the first character in the subsequence * * @param end * The index of the character following the last character in the * subsequence * * @return This writer * * @throws IndexOutOfBoundsException * If {@code start} or {@code end} are negative, {@code start} * is greater than {@code end}, or {@code end} is greater than * {@code csq.length()} * * @since 1.5 */ public CharArrayWriter append(CharSequence csq, int start, int end) { if (csq == null) csq = "null"; return append(csq.subSequence(start, end)); } /** * Appends the specified character to this writer. * * <p> An invocation of this method of the form {@code out.append(c)} * behaves in exactly the same way as the invocation * * <pre> * out.write(c) </pre> * * @param c * The 16-bit character to append * * @return This writer * * @since 1.5 */ public CharArrayWriter append(char c) { write(c); return this; } /** * Resets the buffer so that you can use it again without * throwing away the already allocated buffer. */ public void reset() { count = 0; } /** * Returns a copy of the input data. * * @return an array of chars copied from the input data. */ public char[] toCharArray() { synchronized (lock) { return Arrays.copyOf(buf, count); } } /** * Returns the current size of the buffer. * * @return an int representing the current size of the buffer. */ public int size() { return count; } /** * Converts input data to a string. * @return the string. */ public String toString() { synchronized (lock) { return new String(buf, 0, count); } } /** * Flush the stream. */ public void flush() { } /** * Close the stream. This method does not release the buffer, since its * contents might still be required. Note: Invoking this method in this class * will have no effect. */ public void close() { } }