DocumentFilter that maps lowercase letters to uppercase

   
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;

public class UpcaseFilter extends DocumentFilter {

  public void insertString(DocumentFilter.FilterBypass fb, int offset,
      String text, AttributeSet attr) throws BadLocationException {
    fb.insertString(offset, text.toUpperCase(), attr);
  }

  //no need to override remove(): inherited version allows all removals

  public void replace(DocumentFilter.FilterBypass fb, int offset, int length,
      String text, AttributeSet attr) throws BadLocationException {
    fb.replace(offset, length, text.toUpperCase(), attr);
  }

  public static void main(String[] args) {
    DocumentFilter dfilter = new UpcaseFilter();

    JTextArea jta = new JTextArea();
    JTextField jtf = new JTextField();
    ((AbstractDocument) jta.getDocument()).setDocumentFilter(dfilter);
    ((AbstractDocument) jtf.getDocument()).setDocumentFilter(dfilter);

    JFrame frame = new JFrame("UpcaseFilter");
    frame.getContentPane().add(jta, java.awt.BorderLayout.CENTER);
    frame.getContentPane().add(jtf, java.awt.BorderLayout.SOUTH);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(200, 120);
    frame.setVisible(true);
  }
}

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DocumentFilter that maps lowercase letters to uppercase : Document Event « Swing JFC « Java

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