extends PlainDocument to create alpha and numeric value based field field : Document « Swing Event « Java Tutorial

1. Java Tutorial
2. Swing Event
3. Document

import java.awt.FlowLayout;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;

class JTextFieldFilter extends PlainDocument {
  public static final String ALPHA = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
  public static final String NUMERIC = "0123456789";
  public static final String ALPHA_NUMERIC = ALPHA + NUMERIC;

  protected String acceptedChars = null;

  protected boolean negativeAccepted = false;

  public JTextFieldFilter() {
    this(ALPHA_NUMERIC);
  }

  public JTextFieldFilter(String acceptedchars) {
    acceptedChars = acceptedchars;
  }

  public void setNegativeAccepted(boolean negativeaccepted) {
    if (acceptedChars.equals(ALPHA_NUMERIC)) {
      negativeAccepted = negativeaccepted;
      acceptedChars += "-";
    }
  }

  public void insertString(int offset, String str, AttributeSet attr) throws BadLocationException {
    if (str == null)
      return;
    for (int i = 0; i < str.length(); i++) {
      if (acceptedChars.indexOf(str.valueOf(str.charAt(i))) == -1)
        return;
    }

    if (negativeAccepted) {
      if (str.indexOf(".") != -1) {
        if (getText(0, getLength()).indexOf(".") != -1) {
          return;
        }
      }
    }

    if (negativeAccepted && str.indexOf("-") != -1) {
      if (str.indexOf("-") != 0 || offset != 0) {
        return;
      }
    }

    super.insertString(offset, str, attr);
  }
}

public class Main extends JFrame{
  public static void main(String[] argv) throws Exception {
    new Main();
  }

  public Main() {
    JTextField tf1c;
    JLabel l1c;

    setLayout(new FlowLayout());
    l1c = new JLabel("only float(can be negative)");
    tf1c = new JTextField(10);
    getContentPane().add(l1c);
    getContentPane().add(tf1c);
    JTextFieldFilter jtff = new JTextFieldFilter(JTextFieldFilter.ALPHA_NUMERIC);
    jtff.setNegativeAccepted(true);
    tf1c.setDocument(jtff);
    
    setSize(300,300);
    setVisible(true);
  }
}

15.12.Document
	15.12.1.	Custom Document Filter
	15.12.2.	extends PlainDocument to create a float value type text field
	15.12.3.	extends PlainDocument to create alpha and numeric value based field field
	15.12.4.	Element Walker
	15.12.5.	Implement a document cleaner that maps lowercase letters to uppercase
	15.12.6.	Limit JTextField input to a maximum length