Java练习题22 成绩排序

编写一个应用程序，用户分别从两个文本框输入学生的姓名和分数，程序按成绩排序将这些学生的姓名和分数显示在一个文本区中。

import java.awt.BorderLayout;    
import java.awt.event.ActionEvent;    
import java.awt.event.ActionListener;    
import java.util.ArrayList;    
import java.util.Collections;    
import java.util.Comparator;    
import java.util.HashMap;    
import java.util.Iterator;    
import java.util.LinkedHashMap;    
import java.util.List;    
import java.util.Map;    
import java.util.Map.Entry;        
import javax.swing.JButton;    
import javax.swing.JFrame;    
import javax.swing.JLabel;    
import javax.swing.JPanel;    
import javax.swing.JTextArea;    
import javax.swing.JTextField;     
public class Test extends JFrame {  
    JLabel lname,lscore;
    JTextField tname,tscore;  
    JTextArea show; 
    JButton button;  
    JPanel pan;  
    Map<String,String> studentMap,resultMap;       
    public static void main(String[] args) {  
        new Test();  
    }       
    public Test() {  
        initialize();
        click();
    }       
    public void initialize() {  
        lname=new JLabel("姓名");  
        lscore=new JLabel("成绩");  
        tname =new JTextField(10);  
        tscore=new JTextField(10);  
        button=new JButton("确定");  
        pan=new JPanel();  
        show=new JTextArea();  
        pan.add(lname);  
        pan.add(lscore);  
        pan.add(tname);  
        pan.add(tscore);  
        pan.add(button);  
        add(pan, BorderLayout.NORTH);  
        add(show,BorderLayout.CENTER);  
        setTitle("统计学生姓名和分数:");//设置窗口基础属性  
        setSize(400, 300);  
        setVisible(true);  
        setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);  
        validate();  
        studentMap= new HashMap<String,String>();  
    }  
    public void click() {  
        button.addActionListener(new ActionListener() {               
            public void actionPerformed(ActionEvent e) {  
                save();  
                ShowMap();  
            }  
          });    
    }    
            private void save() {  
                 studentMap.put(tname.getText(),tscore.getText());    
                    resultMap = sortMapByValue(studentMap);   
                    tname.setText("");   
                    tscore.setText("");       
            }  
            public static Map<String, String> sortMapByValue(Map<String, String> map) {    
                if (map == null || map.isEmpty()) {    
                    return null;    
                }    
                Map<String, String> sortedMap = new LinkedHashMap<String, String>();    
                List<Map.Entry<String, String>> entryList = new ArrayList<Map.Entry<String, String>>(map.entrySet());   //将元素存入List中，类型为entry    
                Collections.sort(entryList, new MapValueComparator());    
                Iterator<Map.Entry<String, String>> iter = entryList.iterator();    
                Map.Entry<String, String> tmpEntry = null;    
                while (iter.hasNext()) {    
                    tmpEntry = iter.next();    
                    sortedMap.put(tmpEntry.getKey(), tmpEntry.getValue());   //将List中的元素遍历出来存入map    
                }    
                return sortedMap;    
            }  
            private void ShowMap() {  
                show.setText("");  
                 for(Map.Entry<String,String> entry:resultMap.entrySet()) {        
                        show.append("姓名："+entry.getKey()+"     成绩："+entry.getValue()+"\n");    
                    }           
                }  
            }  
            class MapValueComparator implements Comparator<Map.Entry<String, String>> {    
            public int compare(Entry<String, String> s1, Entry<String, String> s2) {    
                return s1.getValue().compareTo(s2.getValue());    
            }    
        }