实例050 - 使用选择排序法

心法领悟050：如果数组有重复值，应该使用选择排序（selection sort）。

选择排序法从数组中挑选最大值并放在数组最后，而遇到重复的相等值不会做任何处理，所以如果程序允许数组有重复值的情况，建议使用 选择排序法， 因为它的数据交换次数较少，相对速度也会略微提升，这取决于数组中重复值的数量。

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import java.awt.GridBagLayout;
import javax.swing.JScrollPane;
import java.awt.GridBagConstraints;
import javax.swing.JButton;
import java.awt.Insets;
import javax.swing.JTextArea;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.util.Random;

public class SelectSort extends JFrame {
    
    private JPanel contentPane;
    
    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    SelectSort frame = new SelectSort();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }
    
    /**
     * Create the frame.
     */
    public SelectSort() {
        setTitle("\u9009\u62E9\u6392\u5E8F\u7B97\u6CD5\u3011");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 450, 300);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);
        GridBagLayout gbl_contentPane = new GridBagLayout();
        gbl_contentPane.columnWidths = new int[] { 0, 0 };
        gbl_contentPane.rowHeights = new int[] { 0, 0, 0, 0, 0 };
        gbl_contentPane.columnWeights = new double[] { 1.0, Double.MIN_VALUE };
        gbl_contentPane.rowWeights = new double[] { 1.0, 0.0, 1.0, 0.0,
                Double.MIN_VALUE };
        contentPane.setLayout(gbl_contentPane);
        
        JScrollPane scrollPane = new JScrollPane();
        GridBagConstraints gbc_scrollPane = new GridBagConstraints();
        gbc_scrollPane.insets = new Insets(0, 0, 5, 0);
        gbc_scrollPane.fill = GridBagConstraints.BOTH;
        gbc_scrollPane.gridx = 0;
        gbc_scrollPane.gridy = 0;
        contentPane.add(scrollPane, gbc_scrollPane);
        
        textArea1 = new JTextArea();
        scrollPane.setViewportView(textArea1);
        
        JButton button = new JButton("\u751F\u6210\u968F\u673A\u6570");
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                do_button_actionPerformed(e);
            }
        });
        GridBagConstraints gbc_button = new GridBagConstraints();
        gbc_button.insets = new Insets(0, 0, 5, 0);
        gbc_button.gridx = 0;
        gbc_button.gridy = 1;
        contentPane.add(button, gbc_button);
        
        JScrollPane scrollPane_1 = new JScrollPane();
        GridBagConstraints gbc_scrollPane_1 = new GridBagConstraints();
        gbc_scrollPane_1.insets = new Insets(0, 0, 5, 0);
        gbc_scrollPane_1.fill = GridBagConstraints.BOTH;
        gbc_scrollPane_1.gridx = 0;
        gbc_scrollPane_1.gridy = 2;
        contentPane.add(scrollPane_1, gbc_scrollPane_1);
        
        textArea2 = new JTextArea();
        scrollPane_1.setViewportView(textArea2);
        
        JButton button_1 = new JButton("\u9009\u62E9\u6392\u5E8F\u6CD5");
        button_1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                do_button_1_actionPerformed(e);
            }
        });
        GridBagConstraints gbc_button_1 = new GridBagConstraints();
        gbc_button_1.gridx = 0;
        gbc_button_1.gridy = 3;
        contentPane.add(button_1, gbc_button_1);
    }
    
    private int[] array = new int[10];
    private JTextArea textArea1;
    private JTextArea textArea2;
    
    protected void do_button_actionPerformed(ActionEvent e) {
        Random random = new Random();// 创建随机数对象
        textArea1.setText("");// 清空文本域
        for (int i = 0; i < array.length; i++) {// 初始化数组元素
            array[i] = random.nextInt(50);// 生成50以内的随机数
            textArea1.append(array[i]+"  ");// 把数组元素显示的文本域控件中
        }
    }
    
    protected void do_button_1_actionPerformed(ActionEvent e) {
        textArea2.setText("");// 清空文本域
        int index;
        for (int i = 1; i < array.length; i++) {
            index = 0;
            for (int j = 1; j <= array.length - i; j++) {
                if (array[j] > array[index]) {
                    index = j;// 查找最大值
                }
            }
            // 交换在位置array.length-i和index(最大值)两个数
            int temp = array[array.length - i];
            array[array.length - i] = array[index];
            array[index] = temp;
        }
        for (int i = 0; i < array.length; i++) {
            textArea2.append(array[i] + "  ");// 把排序后的数组元素显示到文本域中
        }
    }
}