import java.awt.*;
import java.awt.event.*;
import StringModifier;

/**
 * Objects that listen to buttons and, in response, modify a
 * TextField in an AWT application.  You need one FieldModifier
 * per type of modification per field.
 *
 * @author Samuel A. Rebelsky
 * @version 1.0 of February 1999
 */
public class FieldModifier
  implements ActionListener
{
  // +-----------------------------------------------------------
  // | Fields |
  // +--------+
  
  // No, this doesn't modify these kinds of fields; it modifies
  // the text in a TextField in an AWT.
  
  /** The field to modify. */
  protected TextField field;
  
  /** The string modifier used to modify its contents. */
  protected StringModifier stringmod;
 
  // +--------------+---------------------------------------------
  // | Constructors |
  // +--------------+
  
  /** 
   * Build a new FieldModifier that can modify a particular field
   * using a particular modifier.  
   */
  public FieldModifier(TextField field, StringModifier stringmod) {
    this.field = field;
    this.stringmod = stringmod;
  } // FieldModifier(TextField,StringModifier)
  
  
  // +---------+-------------------------------------------------
  // | Methods |
  // +---------+
  
  /**
   * When asked to perform an action, modify the field.  Used a
   * ``long form'' for the code, which could be expressed more
   * succinctly.
   */
  public void actionPerformed(ActionEvent evt) {
    // Get the contents of the field.
    String str = field.getText();
    // Update the string
    str = stringmod.modify(str);
    // And replace the contents of the field.
    field.setText(str);
  } // actionPerformed(ActionEvent)
} // class FieldModifier