mylist.java

学习java语言

import java.awt.*;
import java.awt.event.*;
class WindowList extends Frame implements ItemListener, ActionListener {
    List list1, list2;
    TextArea text1, text2;
    int index = 0;
    WindowList(){
      setLayout(new FlowLayout());
      list1 = new List(3,false);
      list2 = new List(3,false);
      text1 = new TextArea(2, 20);
      text2 = new TextArea(2, 20);
      list1.add("count 1+2+3~");
      list1.add("count 1*1+2*2+~");
      list1.add("count 1*1*1+2*2*2+~");
      for(int i=1;i<=100;i++)
         list2.add("前"+ i + "项和");
      add(list1);
      add(list2);
      add(text1);
      add(text2);
      list1.addItemListener(this);
      list2.addActionListener(this);
      setSize(400,200);
      setVisible(true);
      validate();
    }
    public void itemStateChanged(ItemEvent e){
      if(e.getItemSelectable()==list1) {
        text1.setText(list1.getSelectedItem());
        index = list1.getSelectedIndex();
      }
    }
    public void actionPerformed(ActionEvent e) {
          int n =list2.getSelectedIndex(),sum=0;
          String name = list2.getSelectedItem();
          switch(index) {
            case 0:
               for(int i=1;i<=n+1;i++)sum += i;
               break;
            case 1:
               for(int i=1;i<=n+1;i++)sum +=i*i;
               break;
            case 2:
               for(int i=1;i<=n+1;i++)sum +=i*i*i;
               break;
            default:
               sum=-100;
          }
          text2.setText(name+"等于"+sum);
    }
}
public class MyList {
  public static void main(String[] args) {
     new WindowList();
  }
}