因为在工作中的class基本都没有覆盖默认的无参数构造方法，所以这个地方理解错了，sorry啊

= - 恩 书上是说 不写的话 默认调用父类的无参构造器 如果没有无参构造器就会报错。。。

回复：62楼
呵呵 没什么关系 你是我师傅~~~能帮我我已经很感谢了！

回复：64楼
不是师傅，互相交流

好的好的 以后还有很多问题要问呢！

package a;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Cat{
     private static void creatAndShowGUI(){
         JFrame frame = new JFrame("Fcuk!");
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         JMenuBar greenMenuBar = new JMenuBar();
         greenMenuBar.setOpaque(true);
         greenMenuBar.setBackground(new Color(248,165,127));
         greenMenuBar.setPreferredSize(new Dimension(200,20));
         JLabel yellowLable = new JLabel();
         yellowLable.setOpaque(true);
         yellowLable.setBackground(new Color(248,213,131));
         yellowLable.setPreferredSize(new Dimension(200,180));
         frame.setJMenuBar(greenMenuBar);
         frame.getContentPane().add(yellowLable,BorderLayout.CENTER);
         frame.pack();
         frame.setVisible(true);
        
     }
     public static void main(String [] args){
         javax.swing.SwingUtilities.invokeLater(new Runnable(){
             public void run(){
                 creatAndShowGUI();
            
             }
         });
        
     }
}

回复：67楼
没有注释，没有美感啊

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
public class Test {
     public static void main(String []args){
         int count,n=512;
         byte [] buffer = new byte [n];
         try {
             System.out.print("输入文字！");
             count = System.in.read(buffer);
             FileOutputStream os = new FileOutputStream("a.txt");
             os.write(buffer,0,count);
             os.close();
             System.out.print("保存成功！");
         } catch (IOException e) {
             // TODO 自动生成 catch 块
             e.printStackTrace();
         }
         try {
             FileInputStream ak = new FileInputStream("a.txt");
             while((ak.read(buffer,0,n)!=-1 )&& n >0);
             {
                 System.out.print(new String(buffer));
             }
             System.out.println();
             ak.close();
         } catch (FileNotFoundException e) {
             // TODO 自动生成 catch 块
             e.printStackTrace();
         } catch (IOException e) {
             // TODO 自动生成 catch 块
             e.printStackTrace();
         }
            
        
     }
}
IO字节流练习

public class Test implements Runnable {
     public Test(){
        
     }
     public void run(){
     int a = 0;
     for(a = 0;a<100;a++){
         try {
             Thread.sleep(1000);
             System.out.print(a);
             System.out.println();
         } catch (InterruptedException e) {
             // TODO 自动生成 catch 块
             System.out.print("被打扰，终止！");
            
         }
        
     }
     }
    
    
}
public class RunDemo {
     public static void main (String [] args) throws InterruptedException{
         System.out.print("线程启动中……");
         Thread t = new Thread(new Test());
         t.start();
         System.out.print("waiting....");
         System.out.println();
         while(t.isAlive()){
             System.out.print("still alive....");
             System.out.println();
             t.join(1000);
         }
        
     }
}