从性能的角度来选择缓冲读卡器或扫描仪

问题描述

从性能优化的角度来看：用Java读取文件 - 更好的是缓冲读取器还是扫描器？

From aperformance optimization point of view: Reading a file in Java - is a buffered reader or scanner better?

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.logging.Level;
import java.util.logging.Logger;


public class BufferedReaderExample {   

    public static void main(String args[]) {

        //reading file line by line in Java using BufferedReader       
        FileInputStream fis = null;
        BufferedReader reader = null;

        try {
            fis = new FileInputStream("C:/sample.txt");
            reader = new BufferedReader(new InputStreamReader(fis));

            System.out.println("Reading File line by line using BufferedReader");

            String line = reader.readLine();
            while(line != null){
                System.out.println(line);
                line = reader.readLine();
            }           

        } catch (FileNotFoundException ex) {
            Logger.getLogger(BufferedReaderExample.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(BufferedReaderExample.class.getName()).log(Level.SEVERE, null, ex);

        } finally {
            try {
                reader.close();
                fis.close();
            } catch (IOException ex) {
                Logger.getLogger(BufferedReaderExample.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
  } 

Output:
Reading File line by line using BufferedReader
first line in file
second line
third line
fourth line
fifth line
last line in file

和扫描仪的另一种方法是..

and the other approach of scanner is..

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.Scanner;

/**
 * @author Javin Paul
 * Java program to read file line by line using Scanner. Scanner is a rather new
 * utility class in Java and introduced in JDK 1.5 and preferred way to read input
 * from console.
 */
public class ScannerExample {


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

       //Scanner Example - read file line by line in Java using Scanner
        FileInputStream fis = new FileInputStream("C:/sample.txt");
        Scanner scanner = new Scanner(fis);

        //reading file line by line using Scanner in Java
        System.out.println("Reading file line by line in Java using Scanner");

        while(scanner.hasNextLine()){
            System.out.println(scanner.nextLine());
        }

        scanner.close();
    }   

}

Output:
Reading file line by line in Java using Scanner
first line in file
second line
third line
fourth line
fifth line
last line in file

推荐答案

BufferedReader 比 Scanner 快得多，因为它缓冲字符，因此每次要从中读取字符时都不必访问该文件。

BufferedReader is a lot faster than Scanner because it buffers the character so you don't have to access the file each time you want to read a char from it.

扫描仪特别有用，例如直接读取原始数据类型，也用于正则表达式。

Scanner are of particular use such as reading primitive data type directly and is also used for regular expressions.

我已经使用了Scanner和BufferedReader，BufferedReader提供了显着的快速性能。你也可以自己测试一下。

I have used Scanner and BufferedReader both and BufferedReader gives significant fast performance. You can test it yourself too.

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