java 讀取文件文本內容_java讀取文本文件

參考自：https://blog.csdn.net/cunchi4221/article/details/107470997?ops_request_misc=&request_id=&biz_id=102&utm_term=java讀取記事本內容&utm_medium=distribute.pc_search_result.none-task-blog-2_allsobaiduweb~default-1-107470997.es_vector_control_group&spm=1018.2226.3001.4187

java 讀取文件文本內容

There are many ways to read a text file in java. Let’s look at java read text file different methods one by one.

有許多方法可以讀取Java中的文本文件。 讓我們一一看一下Java讀取文本文件的不同方法。

1.Java使用Files類讀取文本文件

2.使用FileReader讀取Java中的文本文件

3.Java使用BufferedReader讀取文本文件

4.使用Scanner類讀取Java中的文本文件

示例：

package com.journaldev.files;
 
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.Scanner;
 
public class JavaReadFile {
 
    public static void main(String[] args) throws IOException {
        String fileName = "/Users/pankaj/source.txt";
        
        //using Java 7 Files class to process small files, get complete file data
        readUsingFiles(fileName);
        
        //using Scanner class for large files, to read line by line
        readUsingScanner(fileName);
        
        //read using BufferedReader, to read line by line
        readUsingBufferedReader(fileName);
        readUsingBufferedReaderJava7(fileName, StandardCharsets.UTF_8);
        readUsingBufferedReader(fileName, StandardCharsets.UTF_8);
        
        //read using FileReader, no encoding support, not efficient
        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("Reading text file using FileReader");
        while((line = br.readLine()) != null){
            //process the line
            System.out.println(line);
        }
        br.close();
        fr.close();
        
    }
 
    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("Read text file using InputStreamReader");
        while((line = br.readLine()) != null){
            //process the line
            System.out.println(line);
        }
        br.close();
        
    }
 
    private static void readUsingBufferedReaderJava7(String fileName, Charset cs) throws IOException {
        Path path = Paths.get(fileName);
        BufferedReader br = Files.newBufferedReader(path, cs);
        String line;
        System.out.println("Read text file using BufferedReader Java 7 improvement");
        while((line = br.readLine()) != null){
            //process the line
            System.out.println(line);
        }
        br.close();
    }
 
    private static void readUsingBufferedReader(String fileName) throws IOException {
        File file = new File(fileName);
        FileReader fr = new FileReader(file);
        BufferedReader br = new BufferedReader(fr);
        String line;
        System.out.println("Read text file using BufferedReader");
        while((line = br.readLine()) != null){
            //process the line
            System.out.println(line);
        }
        //close resources
        br.close();
        fr.close();
    }
 
    private static void readUsingScanner(String fileName) throws IOException {
        Path path = Paths.get(fileName);
        Scanner scanner = new Scanner(path);
        System.out.println("Read text file using Scanner");
        //read line by line
        while(scanner.hasNextLine()){
            //process each line
            String line = scanner.nextLine();
            System.out.println(line);
        }
        scanner.close();
    }
 
    private static void readUsingFiles(String fileName) throws IOException {
        Path path = Paths.get(fileName);
        //read file to byte array
        byte[] bytes = Files.readAllBytes(path);
        System.out.println("Read text file using Files class");
        //read file to String list
        @SuppressWarnings("unused")
		List<String> allLines = Files.readAllLines(path, StandardCharsets.UTF_8);
        System.out.println(new String(bytes));
    }
 
}