fileio.java

文件的输入输出。输入名字

		 	   	     file.writeFloat(0);
		 	      }			 	  
		 	}
		 	catch(Exception e)
	 		{
	 			e.printStackTrace();
	 		}
	 		finally
	 		{
	 			try
	 			{	 				    
		 	       file.close();
		 	    }
		 	    catch(Exception e)
		 	    {
		 	    	System.out.println("File can't close properly!");
		 	    }
	 		}	 			 
		}	
 	}
 	
 	public int getRecordNumber()
 	{
 		try
 		{
 			file = new RandomAccessFile(f,"rw");
 			
 			for(int i=1;i <= 100;i++)
 			{
 			   file.seek((long)((i - 1)*Record.RECORD_LENGTH) );
 			   
 			   if (file.readInt() != 0 )//Means the record is existing
 			   { 			   	  
 			   	   recordNumber ++; 			   	 
 			   	   file.seek((long)( (i - 1)*Record.RECORD_LENGTH + 24) );
 			   	   totalScore += file.readFloat(); 			   	   
 			   } 			   
 			}  	
 		}
 		catch (Exception e)
 		{
 			e.printStackTrace();
 			recordNumber = 0;
 		}
 		finally
 		{
 			try
 			{	 				    
	 	       file.close();
	 	    }
	 	    catch(Exception e)
	 	    {
	 	    	System.out.println("File can't close properly!");
	 	    }
 		}	 	
 		return recordNumber;
 	}
 	
 	public float getAverage()
 	{
 	    if (recordNumber == 0)  
	    {
	    	JOptionPane.showMessageDialog(null,"No records in the file",
	 	                                  "Error",JOptionPane.ERROR_MESSAGE);
	 	    return 0;
	 	}
        else 
        {
       	   DecimalFormat formatter = new DecimalFormat("0.00");
       	   return Float.parseFloat( (formatter.format(totalScore/recordNumber)) );
        }	
 	}
 	
 	public String getFilePath()
 	{
 		return filePath;
 	}
 	
 	public void addRecord(Record record)
 	{
 		try
 		{
 			file = new RandomAccessFile(f,"rw");
 			   //Write the record into the file	
 			record.write(file);  			  					
 		}
 		catch(IOException ie)
 		{ 	
 		    ie.printStackTrace();	
 		}
 		finally
 		{
 			try
 			{	 				    
	 	       file.close();
	 	    }
	 	    catch(Exception e)
	 	    {
	 	    	System.out.println("File can't close properly!");
	 	    }
 		}	 	
 	}
 }
 
 class Record 
 {
 	public static final int RECORD_LENGTH = 28; //id:4bytes;name:20bytes;score:4bytes.So 28 bytes total for one record  
 	private String id;   
 	private String name;
 	private float score; 
 	
 	   //Input data should be check before it used
 	public boolean setID(String id)
 	{
 		if (id.equals(""))
	    {
	   	   JOptionPane.showMessageDialog(null,"ID should not be empty",
                                         "Invalid Input",JOptionPane.ERROR_MESSAGE);
           return false;
        } 
        else if (id.length() != 3)
        {
           JOptionPane.showMessageDialog(null,"Invalid ID number",
                                         "Invalid Input",JOptionPane.ERROR_MESSAGE);
           return false;
        }	
           //ID number'scope is 000--100   
 		else if(Integer.parseInt(id) < 0 && Integer.parseInt(id) > 100)
 		{
			JOptionPane.showMessageDialog(null,"Invalid ID number","Invalid Input",JOptionPane.ERROR_MESSAGE);
 			return false;
 		} 		  
 		else 
 		{
 			this.id = id;
 			return true;
 		}	 
 	}
 	
 	   //Input data should be check before it used
 	public boolean setName(String name)
 	{
 		if (name.equals(""))
	    {
	   	   JOptionPane.showMessageDialog(null,"Name should not be empty",
                                      "Invalid Input",JOptionPane.ERROR_MESSAGE);
           return false;
        }
           //The length of the name must be within 20 chars
 		else if (name.length() > 20)
 		{
			JOptionPane.showMessageDialog(null,"The length of the name must be within 20 chars",
 	                                      "Invalid Input",JOptionPane.ERROR_MESSAGE);
 			return false;
 		}
 		else 
	    {
 			while(name.length() < 20) //Make the name's length is 20
 			   name += " ";
 			this.name = name;
 			return true;
 	   	}	    
 	}
 	
 	   //Input data should be check before it used
 	public boolean setScore(String score)
 	{
 		if (score.equals(""))
	    {
	   	   JOptionPane.showMessageDialog(null,"Score should not be empty",
                                      "Invalid Input",JOptionPane.ERROR_MESSAGE);
           return false;
        }
 	    else if (Float.parseFloat(score) < 0 && Float.parseFloat(score) > 100)
 	    { 
 	       JOptionPane.showMessageDialog(null,"Score should be within 0 to 100",
 	                                      "Invalid Input",JOptionPane.ERROR_MESSAGE);
 		   return false;
 		}		    
 			//Score should be within 0 to 100
 	    else 
	    {
		   this.score = Float.parseFloat(score);
	       return true;
	    }
 	}
 	
 	public int getID()
 	{
 		return Integer.parseInt(id);
 	}
 	
 	public String getName()
 	{
 		return name;
 	}
 	
 	public float getScore()
 	{
 		return score;
 	} 	
 	
 	public void write(RandomAccessFile file)
 	{
 		boolean shouldWrite = true;
 	
 		try 
 		{      //Locate the pointer at the specified position
 		       //The head of the file is used to store "recordNumber"(int) and "totalScore"(float).
 		       //So the first record is begin at the 8th byte
 		    file.seek((long)((Integer.parseInt(id)-1) * RECORD_LENGTH ) );		
 		    	
 		       //If the record has all ready existed	   
			if (file.readInt() == Integer.parseInt(id) ) 
			{
				int val = JOptionPane.showOptionDialog(null,"记录已经存在,要替换它 吗?","保存为",
				                                      JOptionPane.OK_CANCEL_OPTION,JOptionPane.WARNING_MESSAGE,null,null,null);
		 		if (val == JOptionPane.OK_OPTION)  //Press OK to override the record
		 		   shouldWrite = true;
		 		else if (val == JOptionPane.CANCEL_OPTION)  //Press Cancel to give up override the record
		 		   shouldWrite = false;
			}
			   
			   //Should write the record into the file
 		    if (shouldWrite)  
 		    {
 		    	file.seek((long)( (Integer.parseInt(id)-1) * RECORD_LENGTH ) );	 		    
	 		       
	 		       //Write the ID number into the file
	 		    file.writeInt(Integer.parseInt(id));	 			   
	 			   
	 			   //Write the name into the file
	 			byte[] buf = new byte[20];
	 			name.getBytes(0,name.length(),buf,0);
	 			file.write(buf);	 			
	 			   
	 			   //Write the score into the file	 			
	 			file.writeFloat(score);	 		
 		    }   		  
 		} 	
 		catch (IOException e)
 		{
 			e.printStackTrace();
 		} 
 		finally
 		{
 			try
 			{	 				    
	 	       file.close();
	 	    }
	 	    catch(Exception e)
	 	    {
	 	    	System.out.println("File can't close properly!");
	 	    }
 		}	 		
 	} 	
 }