content: package com.alipay.api.internal.util.file;
  
  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 $Id: StringBuilderWriter.java 1722253 2015-12-30 00:36:12Z ggregory $
   * @since 2.0
   */
  public class StringBuilderWriter extends Writer implements Serializable {
  
      private static final long          serialVersionUID = -146927496096066153L;
      private final        StringBuilder builder;
  
      /**
       * Constructs a new {@link StringBuilder} instance with default capacity.
       */
      public StringBuilderWriter() {
          this.builder = new StringBuilder();
      }
  
      /**
       * Constructs a new {@link StringBuilder} instance with the specified capacity.
       *
       * @param capacity The initial capacity of the underlying {@link StringBuilder}
       */
      public StringBuilderWriter(final int capacity) {
          this.builder = new StringBuilder(capacity);
      }
  
      /**
       * Constructs a new instance with the specified {@link StringBuilder}.
       *
       * <p>If {@code builder} is null a new instance with default capacity will be created.</p>
       *
       * @param builder The String builder. May be null.
       */
      public StringBuilderWriter(final StringBuilder builder) {
          this.builder = builder != null ? builder : new StringBuilder();
      }
  
      /**
       * Appends a single character to this Writer.
       *
       * @param value The character to append
       * @return This writer instance
       */
      @Override
      public Writer append(final char value) {
          builder.append(value);
          return this;
      }
  
      /**
       * Appends a character sequence to this Writer.
       *
       * @param value The character to append
       * @return This writer instance
       */
      @Override
      public Writer append(final CharSequence value) {
          builder.append(value);
          return this;
      }
  
      /**
       * Appends 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(final CharSequence value, final int start, final int end) {
          builder.append(value, start, end);
          return this;
      }
  
      /**
       * Closing this writer has no effect.
       */
      @Override
      public void close() {
          // no-op
      }
  
      /**
       * Flushing this writer has no effect.
       */
      @Override
      public void flush() {
          // no-op
      }
  
      /**
       * Writes a String to the {@link StringBuilder}.
       *
       * @param value The value to write
       */
      @Override
      public void write(final String value) {
          if (value != null) {
              builder.append(value);
          }
      }
  
      /**
       * Writes 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(final char[] value, final int offset, final int length) {
          if (value != null) {
              builder.append(value, offset, length);
          }
      }
  
      /**
       * Returns 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();
      }
  }
  
  