java - 在 Java 中使用比较器进行数组排序

Question

我在我的程序中实现比较器时遇到问题。

该程序最初是作为如何使用 swing 创建菜单的示例编写的。该程序仅显示菜单、子菜单和带有标题、日期和工作室的电影列表。一个更大的数组将每部电影存储在它自己的数组中，包括它的标题、日期和工作室。

现在，我必须找到一种使用比较器对这些字符串进行排序的方法。像这样:

Arrays.sort(data, new Comparator<String[]>() {

        public int compare(final String[] entry1, final String[] entry2) {
            final String field1 = entry1[0];
            final String field22 = entry2[0];
            return field1.compareTo(field2);
        }
    });

问题是，我从未使用过比较器，也不确定如何实现它。

我在下面添加了原始程序的源代码。

我们将不胜感激任何帮助。

谢谢。

编辑 这个程序类似于 Java 教科书中的程序，但我们被特别告知不要按照教科书的方式解决排序问题。

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

 class MenuExample extends Frame implements ActionListener
 {
     MenuBar mbar;
     Menu menu,submenu;
     MenuItem m1,m2,m3,m4,m5;

     public MenuExample ()
    {
         String[][] data = new String[][]
         {
             new String[] { "Casablanca", "Warner Brothers", "1942" },
             new String[] { "Citizen Kane", "RKO Pictures", "1941" },
             new String[] { "Singin' in the Rain", "MGM", "1952" },
             new String[] { "The Wizard of OZ", "MGM", "1930"}
         };

        // Set frame properties
        setTitle("AWT Menu"); // Set the title
        setSize(800,500); // Set size to the frame
        setLayout(new FlowLayout()); // Set the layout
        setVisible(true); // Make the frame visible
        setLocationRelativeTo(null);  // Center the frame

        // Create the menu bar
        mbar=new MenuBar();

        // Create the menu
        menu=new Menu("Menu");

        // Create the submenu
        submenu=new Menu("Sub Menu");

        // Create MenuItems
        m1=new MenuItem("Menu Item 1");
        m2=new MenuItem("Menu Item 2");
        m3=new MenuItem("Menu Item 3");

        m4=new MenuItem("Menu Item 4");
        m5=new MenuItem("Menu Item 5");
        m1.addActionListener(this);

        // Attach menu items to menu
        menu.add(m1);
        menu.add(m2);
        menu.add(m3);

        // Attach menu items to submenu
        submenu.add(m4);
        submenu.add(m5);

        // Attach submenu to menu
        menu.add(submenu);

        // Attach menu to menu bar
        mbar.add(menu);

        // Set menu bar to the frame
        setMenuBar(mbar);


        JPanel textPanel = new JPanel();

        JTextPane textArea = new JTextPane();


        Dimension textAreaDimensions = new Dimension(100, 300);
        textArea.setPreferredSize(textAreaDimensions);

        //width: 770 height: 1000
        JScrollPane scroll = new JScrollPane (textArea,
            JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
            JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);

        Document doc=textArea.getDocument();
        try
        {
            for(int i=0;i<4;i++)
            {
                for(int j=0;j<3;j++)
                doc.insertString(doc.getLength(),data[i][j]+"\t",
                textArea.getStyle("bold"));
                doc.insertString(doc.getLength(),"\n",
                textArea.getStyle("bold"));
            }//end for

        }//end try

        catch (Exception e) {}
        textPanel.add(scroll);
        add(textPanel);
        validate();
        repaint();
    }//end MenuExample

    public static void main(String args[])
    {
        new MenuExample();
    }//end main

    public void actionPerformed(ActionEvent e)
    {
        System.out.println(e.getActionCommand());
    }//end actionPerformed
}//end class

Answer 1

我只是把这个简单的例子放在一起来展示使用 Comparator 的两种不同方式:

import java.util.Arrays;
import java.util.Comparator;

public class ArraySort
{
  public static void main(String[] args)
  {
     String[][] data = new String[][]
         {
             new String[] { "Casablanca", "Warner Brothers", "1942" },
             new String[] { "Citizen Kane", "RKO Pictures", "1941" },
             new String[] { "Singin' in the Rain", "MGM", "1952" },
             new String[] { "The Wizard of OZ", "MGM", "1930"},
             new String[] { "AaaaaThe Wizard of OZ", "MGM", "1943"}
         };

     Arrays.sort(data, new Comparator<String[]>() {

        @Override
        public int compare(final String[] entry1, final String[] entry2) {
            final String field1 = entry1[0];
            final String field2 = entry2[0];
            return field1.compareTo(field2);
        }
     });

     print(data);

     System.out.println();

     Arrays.sort(data, new SortByDate());

     print(data);

     System.out.println();

     Arrays.sort(data, new SortByCompany());

     print(data);
  }

  public static void print(String[][] data){
    for (String[] array : data){
      for (String s : array){
        System.out.print(s + " ");
      }
      System.out.println();
    } 
  }

}

public class SortByDate implements Comparator<String[]>{
  @Override
  public int compare(final String[] entry1, final String[] entry2) {
    final String field1 = entry1[2];
    final String field2 = entry2[2];
    return field1.compareTo(field2);
  }
}

public class SortByCompany implements Comparator<String[]>{
  @Override
  public int compare(final String[] entry1, final String[] entry2) {
    final String field1 = entry1[1];
    final String field2 = entry2[1];
    return field1.compareTo(field2);
  }
}

输出:

AaaaaThe Wizard of OZ MGM 1943 
Casablanca Warner Brothers 1942 
Citizen Kane RKO Pictures 1941 
Singin' in the Rain MGM 1952 
The Wizard of OZ MGM 1930 

The Wizard of OZ MGM 1930 
Citizen Kane RKO Pictures 1941 
Casablanca Warner Brothers 1942 
AaaaaThe Wizard of OZ MGM 1943 
Singin' in the Rain MGM 1952 

The Wizard of OZ MGM 1930 
AaaaaThe Wizard of OZ MGM 1943 
Singin' in the Rain MGM 1952 
Citizen Kane RKO Pictures 1941 
Casablanca Warner Brothers 1942