18、javaランダムアクセスRandomAccessFileクラス

package com.tij.io.file;

import java.io.IOException;
import java.io.RandomAccessFile;

/**
 *       
 * @author GYJ
 * @date 2014-3-22
 */
public class RandomAccessFileExample {

	/**
	 * RandomAccessFile                 
	 * @param args
	 * @throws IOException 
	 */
	public static void main(String[] args) throws IOException {
		String fileName = "/Users/GYJ/java1.txt";
		//             
		System.out.println(new String(reandCharsFromFile(fileName, 10, 3)));
		//            
		writeData(fileName, "hehe", 5);
	}
	
	/**
	 * RandomAccessFile    
	 * @param fileName	  
	 * @param data		  
	 * @param seek		    
	 * @throws IOException 
	 */
	private static void writeData(String fileName, String data, int seek) throws IOException {
		//'rw' r:read, w:write
		RandomAccessFile file = new RandomAccessFile(fileName,  "rw");
		file.seek(seek);
		file.write(data.getBytes());
		file.close();
	}
	
	/**
	 * 
	 * @param fileName	    
	 * @param seek		    
	 * @param chars		     
	 * @return
	 * @throws IOException 
	 */
	private static byte[] reandCharsFromFile(String fileName, int seek, int chars) throws IOException {
		//'r' read
		RandomAccessFile file= new RandomAccessFile(fileName, "r");
		//    
		file.seek(seek);
		//         
		byte[] bytes = new byte[chars];
		//    
		file.read(bytes);
		file.close();
		return bytes;
	}

}