code: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   * 
   *      http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.io.output;
  
  import java.io.Serializable;
  import java.io.Writer;
  
  /**
   * {@link Writer} implementation that outputs to a {@link StringBuilder}.
   * <p>
   * <strong>NOTE:</strong> This implementation, as an alternative to
   * <code>java.io.StringWriter</code>, provides an <i>un-synchronized</i>
   * (i.e. for use in a single thread) implementation for better performance.
   * For safe usage with multiple {@link Thread}s then
   * <code>java.io.StringWriter</code> should be used.
   *
   * @version $Revision: 1.1.2.1 $ $Date: 2011/01/15 20:32:25 $
   * @since Commons IO 2.0
   */
  public class StringBuilderWriter extends Writer implements Serializable {
  
      private final StringBuilder builder;
  
      /**
       * Construct a new {@link StringBuilder} instance with default capacity.
       */
      public StringBuilderWriter() {
          this.builder = new StringBuilder();
      }
  
      /**
       * Construct a new {@link StringBuilder} instance with the specified capacity.
       *
       * @param capacity The initial capacity of the underlying {@link StringBuilder}
       */
      public StringBuilderWriter(int capacity) {
          this.builder = new StringBuilder(capacity);
      }
  
      /**
       * Construct a new instance with the specified {@link StringBuilder}.
       *
       * @param builder The String builder
       */
      public StringBuilderWriter(StringBuilder builder) {
          this.builder = (builder != null ? builder : new StringBuilder());
      }
  
      /**
       * Append a single character to this Writer.
       *
       * @param value The character to append
       * @return This writer instance
       */
      @Override
      public Writer append(char value) {
          builder.append(value);
          return this;
      }
  
      /**
       * Append a character sequence to this Writer.
       *
       * @param value The character to append
       * @return This writer instance
       */
      @Override
      public Writer append(CharSequence value) {
          builder.append(value);
          return this;
      }
  
      /**
       * Append a portion of a character sequence to the {@link StringBuilder}.
       *
       * @param value The character to append
       * @param start The index of the first character
       * @param end The index of the last character + 1
       * @return This writer instance
       */
      @Override
      public Writer append(CharSequence value, int start, int end) {
          builder.append(value, start, end);
          return this;
      }
  
      /**
       * Closing this writer has no effect. 
       */
      @Override
      public void close() {
      }
  
      /**
       * Flushing this writer has no effect. 
       */
      @Override
      public void flush() {
      }
  
  
      /**
       * Write a String to the {@link StringBuilder}.
       * 
       * @param value The value to write
       */
      @Override
      public void write(String value) {
          if (value != null) {
              builder.append(value);
          }
      }
  
      /**
       * Write a portion of a character array to the {@link StringBuilder}.
       *
       * @param value The value to write
       * @param offset The index of the first character
       * @param length The number of characters to write
       */
      @Override
      public void write(char[] value, int offset, int length) {
          if (value != null) {
              builder.append(value, offset, length);
          }
      }
  
      /**
       * Return the underlying builder.
       *
       * @return The underlying builder
       */
      public StringBuilder getBuilder() {
          return builder;
      }
  
      /**
       * Returns {@link StringBuilder#toString()}.
       *
       * @return The contents of the String builder.
       */
      @Override
      public String toString() {
          return builder.toString();
      }
  }
  