Question

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或扫描器吗？

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..

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

Answer 1

BufferedReader比Scanner要快得多，因为它buffers the character所以每次要从中读取字符时都不必访问该文件。

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。

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。

从性能的角度来选择缓冲读卡器或扫描仪

1 个答案: