A writer for char strings : Auto Grow Array « Collections « Java Tutorial

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/**
 * A writer for char strings.
 * 
 * @author Fred Toussi (fredt@users dot sourceforge.net)
 * @version 1.9.0
 * @since 1.9.0
 */

public class CharArrayWriter {

  protected char[] buffer;

  protected int count;

  public CharArrayWriter(char[] buffer) {
    this.buffer = buffer;
  }

  public void write(int c) {

    if (count == buffer.length) {
      ensureSize(count + 1);
    }

    buffer[count++] = (char) c;
  }

  void ensureSize(int size) {

    if (size <= buffer.length) {
      return;
    }

    int newSize = buffer.length;

    while (newSize < size) {
      newSize *= 2;
    }

    char[] newBuffer = new char[newSize];

    System.arraycopy(buffer, 0, newBuffer, 0, count);

    buffer = newBuffer;
  }

  public void write(String str, int off, int len) {

    ensureSize(count + len);
    str.getChars(off, off + len, buffer, count);

    count += len;
  }

  public void reset() {
    count = 0;
  }

  public void reset(char[] buffer) {
    count = 0;
    this.buffer = buffer;
  }

  public char[] toCharArray() {

    char[] newBuffer = new char[count];

    System.arraycopy(buffer, 0, newBuffer, 0, count);

    return (char[]) newBuffer;
  }

  public int size() {
    return count;
  }

  /**
   * Converts input data to a string.
   * 
   * @return the string.
   */
  public String toString() {
    return new String(buffer, 0, count);
  }
}