import java.io.File;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.RandomAccessFile;

/**

* @author: 马士兵教育

* @create: 2019-09-28 16:20

*/

/**

* 分块读取文件

*

*/

public class RandomAccessFileTest {

public static void main(String[] args) {

File file = new File("doc.txt");

//整个文件的大小

long length = file.length();

//规定块的大小

int blockSize = 1024;

//文件可以被切分成多少个块

int size = (int)Math.ceil(length*1.0/blockSize);

System.out.printf("要被切成《%d》个块",size);

int beginPos = 0;

int actualSize = (int)(blockSize>length?length:blockSize);

for(int i = 0;i<size;i++){

//每次读取块的时候的起始偏移量

beginPos = i*blockSize;

if(i==size-1){

actualSize = (int) length;

}else{

actualSize = blockSize;

length -=actualSize;

}

System.out.println(i+"---》起始位置是："+beginPos+"---->读取的大小是："+actualSize);

// readSplit(i,beginPos,actualSize);

}

}

public static void readSplit(int i,int beginPos,int actualSize){

RandomAccessFile randomAccessFile = null;

try {

randomAccessFile = new RandomAccessFile(new File("doc.txt"),"r");

//表示从哪个偏移量开始读取数据

randomAccessFile.seek(beginPos);

byte[] bytes = new byte[1024];

int length = 0;

while((length = randomAccessFile.read(bytes))!=-1){

if(actualSize>length){

System.out.println(new String(bytes,0,length));

actualSize-=length;

}else{

System.out.println(new String(bytes,0,actualSize));

break;

}

}

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}finally {

try {

randomAccessFile.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

}