java大文件读取效率对比

分别采用三种方式读取大小为74GB共约6亿条记录的文件,BufferedReader 性能最好，RandomAccessFile最差，性能差距超过1百倍

 public static void scannerReader(String filename){
 File f = new File(filename);
 if(f.exists() && f.isFile() && f.length()>0){
 try {
 long times=0;
 long startTime = System.currentTimeMillis();
 Scanner sc = new Scanner(f);
 while(sc.hasNextLine()){
 String temp = sc.nextLine();
 times++;
 }
 sc.close();
 long endTime = System.currentTimeMillis();
 System.out.println("Scanner 执行时间:"+(endTime-startTime) +"当前输出第:"+times+"条数据");
 } catch (FileNotFoundException e) {
 e.printStackTrace();
 } catch (IOException e) {
 e.printStackTrace();
 }
 }
 }
 public static void bufferReader(String filename) throws Exception{
 BufferedReader reader = null;
 try {
 File read= FileUtils.getFile(filename);
 reader = new BufferedReader(new FileReader(read.getAbsoluteFile()));
 String line = null;
 long times=0;
 long startTime = System.currentTimeMillis();
 while((line = reader.readLine()) != null) {
 times++;
 }
 long endTime = System.currentTimeMillis();
 System.out.println("BufferedReader 执行时间:"+(endTime-startTime) +"当前输出第:"+times+"条数据");
 } catch (IOException e) {
 e.printStackTrace();
 }finally {
 }
 }
 public static void ranrReader(String filename)throws Exception{
 RandomAccessFile raf = null;
 FileChannel fc = null;
 try {
 raf = new RandomAccessFile(filename, "r");
 //raf.seek(0);
 fc = raf.getChannel();
 ByteBuffer buffer = ByteBuffer.allocate(100000);
 int readcount = -1;
 long times=0;
 long startTime = System.currentTimeMillis();
 while ((readcount = fc.read(buffer)) != -1) {
 String line = raf.readLine();
 times++;
 }
 long endTime = System.currentTimeMillis();
 System.out.println("RandomAccessFile 执行时间:"+(endTime-startTime) +"当前输出第:"+times+"条数据");
 } catch (Exception e) {
 e.printStackTrace();
 }finally {
 }
 }
 

BufferedReader 执行时间:244007当前输出第:600037902条数据
Scanner 执行时间:2219763当前输出第:600037902条数据
RandomAccessFile 执行时间:35246077当前输出第:600037902条数据