成绩排序

public class Student implements Comparable { 
String name; 
float grade；

public Student(String name,float grade){    this.name = name;    this.grade = grade;}@Overridepublic int compareTo(Student o) {    // TODO Auto-generated method stub    return (int)(o.grade-this.grade);}

} 

import java.awt.FlowLayout; 
import java.awt.Label;

import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.Iterator; 
import java.util.List;

import javax.swing.Box; 
import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JTextArea; 
import javax.swing.JTextField;

public class StudentScore extends JFrame implements ActionListener {

JFrame jf;JTextField jt1;JTextField jt2;JTextArea jta;List<Student> list = new ArrayList<Student>();public static void main(String[] args) {    StudentScore sc = new StudentScore();}StudentScore() {    jf = new JFrame("成绩排序");    jf.setBounds(200, 100, 700, 400);    jf.setLayout(new FlowLayout());    jt1 = new JTextField(10);    jt2 = new JTextField(10);    JButton jbutton = new JButton("确定");    Box box = Box.createHorizontalBox();    box.add(new Label("姓名:"));    box.add(jt1);    box.add(new Label("分数:"));    box.add(jt2);    box.add(Box.createHorizontalStrut(50));    box.add(jbutton);    jf.add(box);    jta = new JTextArea(40, 40);    jf.add(jta);    jf.setVisible(true);    jbutton.addActionListener(this);}@Overridepublic void actionPerformed(ActionEvent arg0) {    jta.setText("");    String name = jt1.getText();    String grade = jt2.getText();    if (!"".equals(name) && !"".equals(grade)) {        list.add(new Student(name, Float.parseFloat(grade)));        jta.append("当前插入的信息为:姓名:" + name + "    成绩:" + grade + "\n");    }    Collections.sort(list);// 对list排序    Iterator<Student> iterator = list.iterator();    Student student;    while (iterator.hasNext()) {        student = iterator.next();        jta.append("name:" + student.name + "    grade:" + student.grade + "\n");    }}

}