JAVA初学者，gui实现简单计算器

package GUI; import java.awt.*; import java.awt.event.*; public class TFMathTest extends Frame{ TextField num1; TextField num2; TextField sum; /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub new TFMathTest().launchFrame(); } public void launchFrame() { num1 = new TextField(); num2 = new TextField(); sum = new TextField(); num1.setColumns(10); num2.setColumns(10); sum.setColumns(15); setLayout(new FlowLayout()); //setSize(500, 30); Label lblPlus = new Label("+"); Button btnEqual = new Button("="); btnEqual.addActionListener(new MyListener(this)); add(num1); add(lblPlus); add(num2); add(btnEqual); add(sum); pack(); setVisible(true); } } class MyListener implements ActionListener { private TFMathTest tfmt; public MyListener(TFMathTest tfmt) { this.tfmt = tfmt; } public void actionPerformed(ActionEvent e) { String s1 = tfmt.num1.getText(); String s2 = tfmt.num2.getText(); int i1 = Integer.parseInt(s1); int i2 = Integer.parseInt(s2); tfmt.sum.setText(String.valueOf(i1 + i2)); } }