Java代审之常见的文件读取方法

Files类

java代码：

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;public class ReadFiles {public static void main(String[] args) throws IOException {String fileName = "C:\\Users\\XXX\\Desktop\\test.txt";//使用Java 7中的Files类处理小文件，获取完整的文件数据readUsingFiles(fileName);}private static void readUsingFiles(String fileName) throws IOException {Path path = Paths.get(fileName);//将文件读取到字节数组byte[] bytes = Files.readAllBytes(path);System.out.println("使用File类读取文件.........");@SuppressWarnings("unused")List<String> allLines = Files.readAllLines(path, StandardCharsets.UTF_8);System.out.println(new String(bytes));}
}

运行截图：

FileReader

java代码：

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;public class ReadFileReader {public static void main(String[] args) throws IOException {String fileName = "C:\\Users\\xxx\\Desktop\\test.txt";//使用FileReader读取，没有编码支持，效率不高readUsingFileReader(fileName);}private static void readUsingFileReader(String fileName) throws IOException {File file = new File(fileName);FileReader fr = new FileReader(file);BufferedReader br = new BufferedReader(fr);String line;System.out.println("使用FileReader读取文本文件......");while ((line = br.readLine()) != null) {//逐行读取System.out.println(line);}br.close();fr.close();}
}

运行截图：

ReadBufferedReader

java代码：

import java.io.*;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;public class ReadBufferedReader {public static void main(String[] args) throws IOException {String fileName = "C:\\Users\\xxx\\Desktop\\test.txt";//使用BufferedReader读取，逐行读取,并设置编码为UTF_8readUsingBufferedReader(fileName, StandardCharsets.UTF_8);}private static void readUsingBufferedReader(String fileName, Charset cs)throws IOException {File file = new File(fileName);FileInputStream fis = new FileInputStream(file);InputStreamReader isr = new InputStreamReader(fis, cs);BufferedReader br = new BufferedReader(isr);String line;System.out.println("使用BufferedReader读取文本文件......");while ((line = br.readLine()) != null) {//逐行读取System.out.println(line);}br.close();}
}

运行截图：

ReadCommonsIo

java代码：

import org.apache.commons.io.FileUtils;import java.io.File;
import java.io.IOException;
import java.nio.charset.StandardCharsets;public class ReadCommonsIo {public static void main(String[] args) throws IOException {String fileName = "C:\\Users\\xxx\\Desktop\\test.txt";readUsingCommonsIo(fileName);}private static void readUsingCommonsIo(String fileName) throws IOException {File file = new File(fileName);System.out.println("使用Commons-io读取文件......");System.out.println(FileUtils.readFileToString(file,StandardCharsets.UTF_8));}
}

maven依赖：

<dependencies><dependency><groupId>commons-io</groupId><artifactId>commons-io</artifactId><version>2.11.0</version></dependency></dependencies>

运行截图：

ReadScanner

import java.io.IOException;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Scanner;public class ReadScanner {public static void main(String[] args) throws IOException {String fileName = "C:\\Users\\xxx\\Desktop\\test.txt";//使用Scanner类来处理大文件，逐行读取readUsingScanner(fileName);}private static void readUsingScanner(String fileName) throws IOException {Path path = Paths.get(fileName);Scanner scanner = new Scanner(path);System.out.println("使用Scanner读取文本文件.....");//逐行读取while (scanner.hasNextLine()) {//逐行处理String line = scanner.nextLine();System.out.println(line);}scanner.close();}
}

运行截图：

ReadRandomAccessFile

import java.io.IOException;
import java.io.RandomAccessFile;public class ReadRandomAccessFile {public static void main(String[] args) throws IOException {String fileName = "C:\\Users\\xxx\\Desktop\\test.txt";//使用RandomAccessFile来实现断点续传读取/下载文件readUsingRandomAccessFile(fileName);}private static void readUsingRandomAccessFile(String fileName) throwsIOException {RandomAccessFile file = new RandomAccessFile(fileName, "r");String str;while ((str = file.readLine()) != null) {System.out.println("使用RandomAccessFile来实现断点续传读取/下载文件......");System.out.println(str);}file.close();}
}

运行截图：

ps：这个方法我想说明一下，通过printIn输出的文本我们可以看出这里他的空白行并不为空，而是\r\n