1 import java.io.Writer;
   2 import java.io.IOException;
   3 import javax.swing.JTextArea;
   4 
   5 /**
   6  * A implementation of the java.io.Writer class
   7  * which facilitates writing to a JTextArea via a stream.
   8  *
   9  * <p><b>Note:</b> There appears to be bug in the Macintosh implementation of
  10  * the JDK 1.1 where a PrintWriter writing to this class will not include the
  11  * correct line feeds for display in a JTextArea.  There is a simple test of
  12  * the "java.version" system property which, if it starts with the String "1.1"
  13  * will cause newlines to be written each time the buffer is flushed.</p>
  14  *
  15  * @author Anthony Eden
  16  */
  17 public class JTextAreaWriter extends Writer {
  18   private boolean closed = false;
  19   private JTextArea textArea;
  20   private StringBuffer buffer;
  21 
  22   /**
  23    * Constructor.
  24    *
  25    * @param textArea The JTextArea to write to.
  26    */
  27   public JTextAreaWriter(JTextArea textArea) {
  28     setTextArea(textArea);
  29   }
  30 
  31   /**
  32    * Set the JTextArea to write to.
  33    *
  34    * @param textArea The JTextArea
  35    */
  36   public void setTextArea(JTextArea textArea) {
  37     if (textArea == null) {
  38       throw new IllegalArgumentException("The text area must not be null.");
  39     }
  40     this.textArea = textArea;
  41   }
  42 
  43   /**
  44    * Close the stream.
  45    */
  46   public void close() {
  47     closed = true;
  48   }
  49 
  50   /**
  51    * Flush the data that is currently in the buffer.
  52    *
  53    * @throws IOException
  54    */
  55   public void flush() throws IOException {
  56     if (closed) {
  57       throw new IOException("The stream is not open.");
  58     }
  59     // the newline character should not be necessary.  The PrintWriter
  60     // should autmatically put the newline, but it doesn't seem to work
  61     textArea.append(getBuffer().toString());
  62     if (System.getProperty("java.version").startsWith("1.1")) {
  63       textArea.append("\n");
  64     }
  65     textArea.setCaretPosition(textArea.getDocument().getLength());
  66     buffer = null;
  67   }
  68 
  69   /**
  70    * Write the given character array to the output stream.
  71    *
  72    * @param charArray The character array
  73    * @throws IOException
  74    */
  75   public void write(char[] charArray) throws IOException {
  76     write(charArray, 0, charArray.length);
  77   }
  78 
  79   /**
  80    * Write the given character array to the output stream beginning from
  81    * the given offset and proceeding to until the given length is reached.
  82    *
  83    * @param charArray The character array
  84    * @param offset The start offset
  85    * @param length The length to write
  86    * @throws IOException
  87    */
  88   public void write(char[] charArray, int offset, int length) throws IOException {
  89     if (closed) {
  90         throw new IOException("The stream is not open.");
  91     }
  92     getBuffer().append(charArray, offset, length);
  93   }
  94 
  95   /**
  96    * Write the given character to the output stream.
  97    *
  98    * @param c The character
  99    * @throws IOException
 100    */
 101   public void write(int c) throws IOException {
 102     if (closed) {
 103       throw new IOException("The stream is not open.");
 104     }
 105     getBuffer().append((char) c);
 106   }
 107 
 108   /**
 109    * Write the given String to the output stream.
 110    *
 111    * @param string The String
 112    * @throws IOException
 113    */
 114   public void write(String string) throws IOException {
 115     if (closed) {
 116       throw new IOException("The stream is not open.");
 117     }
 118     getBuffer().append(string);
 119   }
 120 
 121   /**
 122    * Write the given String to the output stream beginning
 123    * from the given offset
 124    * and proceeding to until the given length is reached.
 125    *
 126    * @param string The String
 127    * @param offset The start offset
 128    * @param length The length to write
 129    * @throws IOException
 130    */
 131   public void write(String string, int offset, int length) throws IOException {
 132     if (closed) {
 133       throw new IOException("The stream is not open.");
 134     }
 135     getBuffer().append(string.substring(offset, length));
 136   }
 137 
 138   // protected methods
 139 
 140   /**
 141    * Get the StringBuffer which holds the data prior to writing via
 142    *  a call to the <code>flush() method. This method should
 143    *  never return null.
 144    *
 145    * @return A StringBuffer
 146    */
 147   protected StringBuffer getBuffer() {
 148     if (buffer == null) {
 149       buffer = new StringBuffer();
 150     }
 151     return buffer;
 152   }
 153 }