linestrchange.java

用java写的unix文件管理模拟系统

import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.FileNotFoundException;
import java.util.Vector;

/**
 * 修改文件中的某行字符串
 * @author bread
 * version 1.0
 */
public class LineStrChange 
{
	private static String fileName;
	private static BufferedReader bReader;
	private static PrintWriter pWriter;
	private static Vector<String> infos
						= new Vector<String>();
	
	public static void setFileName( String name )
	{
		fileName = name;
	}
	
	public static void changeLine
				( String info, int lineNum )
	{
		editLine( info, lineNum, false );
	}
	
	public static void deleteLine( int lineNum )
	{
		editLine( "", lineNum, true );
	}
	
	private static void editLine( String info, int lineNum, boolean isDelete )
	{
		init();
		infos.clear();
		String line = readLine();
		int count = 1;
		while( line != null )
		{
			if( lineNum == count )
			{
				if( !isDelete )
				{
					infos.add( info );
				}
			}
			
			else
			{
				infos.add( line );
			}
			count ++;
			line = readLine();
		}
		writeFile();
	}

	
	
	private static void writeFile()
	{
		FileWriter writer = null;
		try
		{
			writer = new FileWriter( fileName );
		}
		
		catch( IOException e )
		{
			e.printStackTrace();
		}
		
		pWriter = new PrintWriter( writer );
		
		for( int i=0; i<infos.size(); i++ )
		{
			String newInfo = infos.get( i );
			if( i==infos.size()-1 )
			{
				pWriter.print( newInfo );
			}
			
			else
			{
				pWriter.println( newInfo );
			}
		}
		
		pWriter.flush();
	}
	
	
	private static void init()
	{
		FileReader reader = null;
		try
		{
			if( bReader != null )
			{
				bReader.close();
			}
			reader = new FileReader( fileName );
		}
		
		catch( FileNotFoundException e )
		{
			e.printStackTrace();
		}
		
		catch( IOException e )
		{
			e.printStackTrace();
		}
		
		bReader = new BufferedReader( reader );
		
		infos.clear();
	}
	
	
	private static String readLine()
	{
		String lineInfo = null;
		try
		{
			lineInfo = bReader.readLine();
		}
		
		catch( IOException e )
		{
			e.printStackTrace();
		}
		
		return lineInfo;
	}
}