代碼是同學(xué)那拷的沒(méi)問(wèn)題，但是在my上就報(bào)這個(gè)錯(cuò)誤

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//package java_test6;

import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class ExRate {

public static void main(String[] args) {
    JFrame f = new JFrame(); //窗口容器
    f.setSize(200, 200);
    JTextArea t1 = new JTextArea(1, 5);//指定行列
    JTextArea t2 = new JTextArea(1, 5);
    JButton b1 = new JButton("test it");
    Label l1, l2;
    l1 = new Label();
    l2 = new Label();
    l1.setText("Please Enter The Number");
    l2.setText("The Result Of The Test");
    Choice c = new Choice();  //這里需final
    c.add("RMB");
    c.add("Euro");
    c.add("USA$");
    Choice c1 = new Choice();
    c1.add("RMB");
    c1.add("Euro");
    c1.add("USA$");
    f.add(l1);
    f.add(t1);
    f.add(c);
    f.add(l2);
    f.add(t2);
    f.add(c1);
    f.add(b1);
    b1.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            if (c.getSelectedItem() == "RMB" && c1.getSelectedItem() == "USA$") {
                String s;
                s = t1.getText();
                int q = 0;
                q = Integer.parseInt(s);
                double w;
                w = q * 0.1506;
                String r = Double.toString(w);
                t2.setText(r);
            } else if (c.getSelectedItem() == "USA$" && c1.getSelectedItem() == "RMB") {
                String s;
                s = t1.getText();
                int q = 0;
                q = Integer.parseInt(s);
                double w;
                w = q * 6.6391;
                String r = Double.toString(w);
                t2.setText(r);
            } else if (c.getSelectedItem() == "RMB" && c1.getSelectedItem() == "Euro") {
                String s;
                s = t1.getText();
                int q = 0;
                q = Integer.parseInt(s);
                double w;
                w = q * 0.1297;
                String r = Double.toString(w);
                t2.setText(r);
            } else if (c.getSelectedItem() == "Euro" && c1.getSelectedItem() == "RMB") {
                String s;
                s = t1.getText();
                int q = 0;
                q = Integer.parseInt(s);
                double w;
                w = q * 7.7107;
                String r = Double.toString(w);
                t2.setText(r);
            } else if (c.getSelectedItem() == "USA$" && c1.getSelectedItem() == "Euro") {
                String s;
                s = t1.getText();
                int q = 0;
                q = Integer.parseInt(s);
                double w;
                w = q * 0.8610;
                String r = Double.toString(w);
                t2.setText(r);
            } else if (c.getSelectedItem() == "Euro" && c1.getSelectedItem() == "USA$") {
                String s;
                s = t1.getText();
                int q = 0;
                q = Integer.parseInt(s);
                double w;
                w = q * 1.1614;
                String r = Double.toString(w);
                t2.setText(r);
            }
        }
    });
    f.setLayout(new FlowLayout());
    f.setVisible(true);
    f.addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
            System.exit(0);
        }
    });
}

}*