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import java.applet.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class InputDemo extends Applet {
TextField text1, text2;
public void init() {
text1 = new TextField(10);
text2 = new TextField(10);
add(text1);
add(text2);
text1.addKeyListener(new KeyAdapter(){
public void keyReleased(KeyEvent e) {
try {
long n = Long.parseLong(text1.getText());
text2.setText(String.valueOf(n * n));
} catch (NumberFormatException ex) {
text2.setText("请输入一个整数");
}
}
});
}
}