Java大文件读取

1.使用RandomAccess读取

import java.io.FileNotFoundException;

import java.io.FileReader;

import java.io.IOException;

import java.io.RandomAccessFile;

import java.util.Scanner;

public class TestPrint {

public static void main(String[] args) throws IOException {

String path = "你要读的文件的路径";

RandomAccessFile br=new RandomAccessFile(path,"rw");//这里rw看你了。要是之都就只写r

String str = null, app = null;

int i=0;

while ((str = br.readLine()) != null) {

i++;

app=app+str;

if(i>=100){//假设读取100行

i=0;

//这里你先对这100行操作，然后继续读

app=null;

}

}

br.close();

}

}
2.使用BufferReader设置缓冲区大小

void largeFileIO(String inputFile, String outputFile) {

        try {

            BufferedInputStream bis = new BufferedInputStream(new FileInputStream(new File(inputFile)));

            BufferedReader in = new BufferedReader(new InputStreamReader(bis, "utf-8"), 10 * 1024 * 1024);//10M缓存

            FileWriter fw = new FileWriter(outputFile);

            while (in.ready()) {

                String line = in.readLine();

                fw.append(line + " ");

            }

            in.close();

            fw.flush();

            fw.close();

        } catch (IOException ex) {

            ex.printStackTrace();

        }