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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);
}
}
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