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; /** * A character stream that collects its output in a string buffer, which can * then be used to construct a string. * <p> * Closing a {@code StringWriter} has no effect. The methods in this class * can be called after the stream has been closed without generating an * {@code IOException}. * * @author Mark Reinhold * @since 1.1 */ public class StringWriter extends Writer { private StringBuffer buf; /** * Create a new string writer using the default initial string-buffer * size. */ public StringWriter() { buf = new StringBuffer(); lock = buf; } /** * Create a new string writer using the specified initial string-buffer * size. * * @param initialSize * The number of {@code char} values that will fit into this buffer * before it is automatically expanded * * @throws IllegalArgumentException * If {@code initialSize} is negative */ public StringWriter(int initialSize) { if (initialSize < 0) { throw new IllegalArgumentException("Negative buffer size"); } buf = new StringBuffer(initialSize); lock = buf; } /** * Write a single character. */ public void write(int c) { buf.append((char) c); } /** * Write a portion of an array of characters. * * @param cbuf Array of characters * @param off Offset from which to start writing characters * @param len Number of characters to write * * @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 cbuf[], int off, int len) { if ((off < 0) || (off > cbuf.length) || (len < 0) || ((off + len) > cbuf.length) || ((off + len) < 0)) { throw new IndexOutOfBoundsException(); } else if (len == 0) { return; } buf.append(cbuf, off, len); } /** * Write a string. */ public void write(String str) { buf.append(str); } /** * Write a portion of a string. * * @param str String to be written * @param off Offset from which to start writing characters * @param len Number of characters to write * * @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) { buf.append(str, off, off + len); } /** * 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 StringWriter append(CharSequence csq) { write(String.valueOf(csq)); 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>{@code * 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 StringWriter 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 StringWriter append(char c) { write(c); return this; } /** * Return the buffer's current value as a string. */ public String toString() { return buf.toString(); } /** * Return the string buffer itself. * * @return StringBuffer holding the current buffer value. */ public StringBuffer getBuffer() { return buf; } /** * Flush the stream. */ public void flush() { } /** * Closing a {@code StringWriter} has no effect. The methods in this * class can be called after the stream has been closed without generating * an {@code IOException}. */ public void close() throws IOException { } }