java中的对象有问题吗？

Question

我正在制作一个根据用户输入是或否做出反应的窗口。我在这部分代码中遇到了问题：

public class Mywindow {

public static void main (String [] args){
    windowcontinued object = new windowcontinued();
    object.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //ISSUE HERE
    object.setSize(700, 1024); //ISSUE HERE
    object.setVisible(true); //ISSUE HERE
                                         }
                }

这些简单的操作应该确保程序在关闭时终止，具有一定的大小，并且是可见的。但出于某种原因，在所有三个操作中，我都收到错误消息：

 The method setDefaultCloseOperation(int) is undefined for the type windowcontinued

The method setSize(int, int) is undefined for the type windowcontinued

The method setVisible(boolean) is undefined for the type windowcontinued

虽然，所有这些都应该在导入后已经定义。完整代码如下：

主要代码：

package Myguipackage;

import javax.swing.JOptionPane;
import javax.swing.JFrame;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class Mywindow {

public static void main (String [] args){
    windowcontinued object = new windowcontinued();
    object.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    object.setSize(700, 1024);
    object.setVisible(true);

                                         }
                }

其他类：

package Myguipackage;
import javax.swing.JOptionPane;
import javax.swing.JFrame;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class Windowcontinued{

public JLabel text;
public JTextField textfield;

public windowcontinued(){  //Constructor
/*  super("CHAT");
    setLayout(new FlowLayout());   */   

    text = new JLabel ("Would you like to talk to me?");
        text.add(text);

    textfield = new JTextField ("Yes or no? Erase this and type in your answer!");




                   }






 class hear implements ActionListener{



    public void actionPerformed(ActionEvent event){

        String string = "";

        if(event.getSource()==textfield)
            string = String.format("You typed in %s", event.getActionCommand());

         JOptionPane.showMessageDialog(null, string); //Open a new window that displays String string, which has changed based on which field you hit enter on.




                                                  }



                                         }


                        }

按照 fdsa 的建议使用 extends 关键字后，这里是新代码：

包Myguipackage;

import javax.swing.JFrame;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class mywindow extends JFrame{

public static void main (String [] args){
    windowcontinued object = new windowcontinued();
    object.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    object.setSize(700, 1024);
    object.setVisible(true);
                                         }
                }

Class windowcontinued 还是一样的。

Answer 1

正如其他发帖者所说，命名类时请遵循 java 命名约定。它使您的代码更易于理解。

您似乎对import 声明的目的感到困惑。导入对象时，只能在该类型的对象上使用其方法。如果您希望您的类模仿现有类的功能，您需要 extend 原始类，而不仅仅是 import 它。