Question

我目前正在开发一个java程序，它有一个JCombo框，用户可以在其中选择一个形状，并且该形状是随机生成的多次。我正在使用命令行来运行它并使用记事本。我正在使用最新的JDK版本。如何修改我的代码以便在新版本上编译..？

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.Random;
import javax.swing.*;

public class Hw1b extends JFrame
{
    public Hw1b()
    {
        super("Hw1b");
        final ComboPanel comboPanel = new ComboPanel();
        String[] shapeItems = {
            "Square", "Oval", "Rectangle", "Circle"
            //"Circle", "Square", "Oval", "Rectangle"
        };

        JComboBox shapeBox = new JComboBox(shapeItems);
        shapeBox.addItemListener(new ItemListener()
        {
            public void itemStateChanged(ItemEvent e)
            {
                if(e.getStateChange() == ItemEvent.SELECTED)
                {
                    String item = (String)e.getItem();
                    if(item.equals("Square"))
                        comboPanel.makeSquares();
                    if(item.equals("Oval"))
                        comboPanel.makeOvals();
                    if(item.equals("Rectangle"))
                        comboPanel.makeRectangles();
                    if(item.equals("Circle"))
                        comboPanel.makeCircles();
                    /*  
                    if(item.equals("Circle"))
                        comboPanel.makeSquares();
                    if(item.equals("Square"))
                        comboPanel.makeOvals();
                    if(item.equals("Oval"))
                        comboPanel.makeRectangles();
                    if(item.equals("Rectangle"))
                        comboPanel.makeCircles();
*/                      
                }
            }
        });

        //position and set size of Jpanel 
        JPanel southPanel = new JPanel();
        southPanel.add(shapeBox);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        getContentPane().add(comboPanel, "Center");
        getContentPane().add(southPanel, "South");
        setSize(600,400);
        setLocation(200,200);
        setVisible(true);
    }

    private class ComboPanel extends JPanel
    {
        int w, h;
        Random seed;
        static final int
            OVAL = 0,
            RECT = 1;
        int shapeType = -1;

        public ComboPanel()
        {
            seed = new Random();
            setBackground(Color.white);
        }

        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D)g;
            g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            int width = getWidth();
            int height = getHeight();
            int x, y;
            Shape s = null;
            for(int i = 0; i < 20; i++)
            {
                x = seed.nextInt(width - w);
                y = seed.nextInt(height - h);
                switch(shapeType)
                {
                    case OVAL:
                        s = new Ellipse2D.Double(x, y, w, h);
                        break;
                    case RECT:
                        s = new Rectangle2D.Double(x, y, w, h);
                }
                if(shapeType > -1)
                    g2.draw(s);
            }
        }

        public void makeSquares()
        {
            shapeType = RECT;
            w = 50;
            h = 50;
            repaint();
        }

        public void makeOvals()
        {
            shapeType = OVAL;
            w = 80;
            h = 60;
            repaint();
        }

        public void makeRectangles()
        {
            shapeType = RECT;
            w = 80;
            h = 40;
            repaint();
        }

        public void makeCircles()
        {
            shapeType = OVAL;
            w = 75;
            h = 75;
            repaint();
        }
    }

    public static void main(String[] args)
    {
        new Hw1b();
    }
}

Answer 1

JComboBox是“原始”类型，这意味着您需要提供它将要使用的实际类型。您关注的消息不是错误，而是试图引起您的注意：

JComboBox shapeBox = new JComboBox(shapeItems);

为了使您的代码类型安全，您需要明确说明您的JComboBox将与字符串一起使用：

JComboBox<String> shapeBox = new JComboBox<>(shapeItems);

如果您希望了解有关原始类型和泛型的更多信息，我建议您浏览this post。

Java错误代码：未经检查或不安全的操作......？

1 个答案: