初学Java必会的几道练习题(上)

学java 时基础知识没有学好，学到的现在也忘得差不多了，补补。
（下）不大好就不转了。

转自：http://513500795.qzone.qq.com/blog/1215508623?ptlang=2052

1.文件加密器 
import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*; 
import javax.swing.event.*; 
import java.io.*; 
public class FileLock extends JFrame implements ActionListener 
{ 
private JMenuBar menuBar; 
private JMenu file; 
private JLabel fileName; 
private JButton replace,newfile; 
public FileLock() 
{ 
  super("杨明文件加密器"); 
  menuBar=new JMenuBar(); 
  fileName=new JLabel("请选择需要加密的文件"); 
  file=new JMenu("File"); 
  replace=new JButton("覆盖原文件"); 
  newfile=new JButton("创建新文件"); 
  init(); 
  showFrame(); 
} 
public void init() 
{ 
  JMenuItem item=null; 
  file.add(item=new JMenuItem("打开..."));item.addActionListener(this); 
  file.add(item=new JMenuItem("退出"));item.addActionListener(this); 
  replace.addActionListener(this); 
  newfile.addActionListener(this); 
  menuBar.add(file); 
  this.setLayout(new FlowLayout(FlowLayout.CENTER)); 
  this.add(replace); 
  this.setJMenuBar(menuBar); 
  this.add(newfile); 
  this.add(fileName); 
} 
public void showFrame() 
{ 
  this.setSize(300,120); 
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
  this.setVisible(true); 
  this.setResizable(false); 
} 
public void actionPerformed(ActionEvent e) 
{ 
  String command=e.getActionCommand(); 
  if(command.equals("打开...")) 
  { 
   JFileChooser jfc=new JFileChooser(); 
   jfc.showOpenDialog(this); 
   try 
   { 
    if(!(jfc.getName(jfc.getSelectedFile())).equals("")) 
    { 
     fileName.setText(jfc.getSelectedFile().getPath()); 
    } 
   } 
   catch(Exception ex) 
   { 
     
   } 
  } 
  if(command.equals("覆盖原文件")) 
  { 
   RandomAccessFile rafs=null; 
   if(fileName.getText().equals("请选择需要加密的文件")) 
   { 
    JOptionPane.showMessageDialog(this,"请选择需要加密的文件"); 
   } 
   else 
   { 
    try 
    { 
     rafs=new RandomAccessFile(fileName.getText(),"rw"); 
     int number=-1,input=0; 
     while((number=rafs.read())!=-1) 
     { 
      fileName.setText("正在加密..."); 
      input=number^10; 
      rafs.seek(rafs.getFilePointer()-1); 
      rafs.write(input); 
     } 
     JOptionPane.showMessageDialog(this,"文件加密成功!"); 
     fileName.setText("请选择需要加密的文件"); 
    } 
    catch(Exception ea) 
    { 
     
    } 
    finally 
    { 
     if(rafs!=null) 
     { 
      try 
      { 
       rafs.close(); 
      } 
      catch(IOException eb) 
      {} 
     }     
    } 
   } 
  } 
  if(command.equals("创建新文件")) 
  { 
   OutputStream os=null; 
   RandomAccessFile rafs=null; 
   if(fileName.getText().equals("请选择需要加密的文件")) 
   { 
    JOptionPane.showMessageDialog(this,"请选择需要加密的文件"); 
   } 
   else 
   { 
    try 
    { 
     rafs=new RandomAccessFile(fileName.getText(),"rw"); 
     os=new FileOutputStream(fileName.getText()+".ym"); 
     int number=-1,input=0; 
     while((number=rafs.read())!=-1) 
     { 
      fileName.setText("正在加密..."); 
      input=number^10; 
      os.write(input); 
     } 
     os.flush(); 
     JOptionPane.showMessageDialog(this,"文件加密成功!"); 
     fileName.setText("请选择需要加密的文件"); 
    } 
    catch(Exception ea) 
    { 
     
    } 
    finally 
    { 
     if(rafs!=null&&os!=null) 
     { 
      try 
      { 
       rafs.close(); 
       os.close(); 
      } 
      catch(IOException eb) 
      { 
       
      } 
     }     
    } 
   } 
  } 
} 
public static void main(String[] args) 
{ 
  new FileLock(); 
} 
} 
2.倒计时牌 
import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*; 
import javax.swing.event.*; 
import java.util.*; 
public class OlympicTime extends JFrame implements Runnable 
{ 
JLabel[] labels=new JLabel[9]; 
JPanel jp1,jp2; 
public OlympicTime() 
{ 
  super("奥运会倒计时"); 
  labels[0]=new JLabel("距离2008年奥运会（这儿可以换别的，下面的时间对应改就OK）还有:"); 
  labels[1]=new JLabel("00"); 
  labels[2]=new JLabel("天"); 
  labels[3]=new JLabel("00"); 
  labels[4]=new JLabel("时"); 
  labels[5]=new JLabel("00"); 
  labels[6]=new JLabel("分"); 
  labels[7]=new JLabel("00"); 
  labels[8]=new JLabel("秒"); 
  init(); 
  showMe(); 
} 
public void init() 
{ 
  jp1=new JPanel();                                                                               
  jp2=new JPanel(); 
  jp2.add(labels[0]); 
  for(int i=1;i<labels.length;i++) 
  { 
   jp1.add(labels); 
   if(i%2!=0) 
   { 
    labels.setForeground(Color.red); 
   } 
  } 
  this.add(jp2,BorderLayout.NORTH); 
  this.add(jp1,BorderLayout.CENTER); 
} 
public void showMe() 
{ 
  this.setSize(300,100); 
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
  this.setResizable(false); 
  this.setVisible(true); 
} 
public void run() 
{ 
  GregorianCalendar olympic=new GregorianCalendar(2008,7,8,20,8,0); 
  long olympictime=olympic.getTimeInMillis(); 
  while(true){ 
   Calendar now=Calendar.getInstance(); 
   long nowtime=now.getTimeInMillis(); 
   try{ 
   Thread.sleep(1000); 
   }catch(Exception e){ 
     
   } 
   long day=(olympictime-nowtime)/3600/24/1000; 
   long hour=((olympictime-nowtime)/3600000)%24; 
   long minute=((olympictime-nowtime)/60000)%60; 
   long second=((olympictime-nowtime)/1000)%60; 
   labels[1].setText(day+""); 
   labels[3].setText(hour+""); 
   labels[5].setText(minute+""); 
   labels[7].setText(second+""); 
  } 
} 
        public static void main(String[] args) 
        { 
                Runnable runnable=new OlympicTime(); 
                Thread time=new Thread(runnable); 
                time.start(); 
        } 
} 
3.模拟栈 
import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*; 
import javax.swing.event.*; 
public class StackFrame extends JFrame implements ActionListener 
{ 
private JButton newProducer,newConsumer,stopButton; 
private JProgressBar progressBar; 
private JTextArea progressText; 
private JPanel jpsouth; 
private JScrollPane jpcenter; 
public final int MAX_SIZE; 
int count; 
int[] a; 
boolean STOP=false; 
public StackFrame() 
{ 
  MAX_SIZE=100; 
} 
public StackFrame(int size) 
{ 
  super("添加删除进程演示"); 
  newProducer=new JButton("New Producer"); 
  newConsumer=new JButton("New Consumer"); 
  stopButton=new JButton("Stop"); 
  progressBar=new JProgressBar(1,size); 
  progressText=new JTextArea(); 
  jpcenter=new JScrollPane(progressText); 
  jpsouth=new JPanel(); 
  count=0; 
  MAX_SIZE=size; 
  a=new int[size]; 
  init(); 
  showFrame(); 
} 
public void init() 
{ 
  progressBar.setStringPainted(true); 
  progressText.append("This is the progress:\n"); 
  jpsouth.setLayout(new FlowLayout(FlowLayout.LEFT)); 
  jpsouth.add(newProducer); 
  jpsouth.add(newConsumer); 
  jpsouth.add(progressBar); 
  jpsouth.add(stopButton); 
  newProducer.addActionListener(this); 
  newConsumer.addActionListener(this); 
  stopButton.addActionListener(this); 
  this.add(jpcenter,BorderLayout.CENTER); 
  this.add(jpsouth,BorderLayout.SOUTH); 
} 
public void actionPerformed(ActionEvent e) 
{ 
  String command=e.getActionCommand(); 
  if(command.equals("New Producer")) 
  { 
   STOP=false; 
   Runnable push1=this.new Producer(); 
   Thread stackPush1=new Thread(push1); 
   stackPush1.start(); 
  } 
  if(command.equals("New Consumer")) 
  { 
   STOP=false; 
   Runnable pop=this.new Consumer(); 
   Thread stackPop=new Thread(pop); 
   stackPop.start(); 
  } 
  if(command.equals("Stop")||command.equals("Start")) 
  { 
   STOP=true; 
  } 
   
} 
public void showFrame() 
{ 
  this.setSize(600,500); 
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
  this.setVisible(true); 
  this.setResizable(false); 
} 
public synchronized void push() 
{ 
  this.progressText.append("Push a data COUNT+"+count+"!\n"); 
  while(count==MAX_SIZE) 
  { 
   this.progressText.append("The stack is full!!!("+count+" elements)"); 
   try 
   { 
    this.wait(); 
   } 
   catch(InterruptedException e) 
   { 
    e.printStackTrace(); 
   } 
  } 
  a[count++]=count; 
  this.progressBar.setValue(count); 
  this.notifyAll();   
} 
public synchronized int pop() 
{ 
  this.progressText.append("Pop a data COUNT+"+count+"!\n"); 
  while(count==0) 
  { 
   this.progressText.append("The stack is empty!!!("+count+" elements)"); 
   this.progressBar.setValue(count); 
   try{ 
    this.wait(); 
   }catch(InterruptedException e){ 
    e.printStackTrace(); 
   } 
  } 
  this.progressBar.setValue(count); 
  this.notifyAll(); 
  return a[--count]; 
} 
class Producer implements Runnable 
{ 
  public void run() 
  { 
   while(true) 
   { 
    if(STOP) 
    { 
     break; 
    }     
    try{ 
     Thread.sleep(300); 
    }catch(Exception e){ 
     e.printStackTrace(); 
    } 
    StackFrame.this.push(); 
   } 
  } 
} 
class Consumer implements Runnable 
{ 
  public void run() 
  { 
   while(true) 
   {     
    if(STOP) 
    { 
     break; 
    } 
    try{ 
     Thread.sleep(400); 
    }catch(Exception e){ 
     e.printStackTrace(); 
    } 
    StackFrame.this.pop(); 
   } 
  } 
} 
public static void main(String[] args) 
{ 
  StackFrame stackFrame=new StackFrame(100); 
} 
}