java逐行读取文件_Java逐行读取文件

不念不忘少年蓝@ 2023-02-28 06:17 14阅读 0赞

java逐行读取文件

Today we will look into different java read file line by line methods. Sometimes we have to read file line by line to a String, for example calling a method by passing each line as String to process it.

今天，我们将逐行研究不同的Java读取文件。 有时我们必须逐行读取文件到String，例如，通过将每一行作为String传递来处理它来调用方法。

## Java逐行读取文件 **(****Java Read File line by line****)** ##

We can read file line by line using different ways. Let’s look at some of them.

我们可以使用不同的方式逐行读取文件。 让我们看看其中的一些。

### Java使用BufferedReader逐行读取文件 **(****Java Read File line by line using BufferedReader****)** ###

We can use `java.io.BufferedReader` `readLine()` method to read file line by line to String. This method returns null when end of file is reached. Below is a simple program showing example for java read file line by line using BufferedReader.

我们可以使用`java.io.BufferedReader` `readLine()`方法逐行读取文件到String。 到达文件末尾时，此方法返回null。 下面是一个简单的程序，显示了使用BufferedReader逐行读取Java文件的示例。

package com.journaldev.readfileslinebyline;
    
    import java.io.BufferedReader;
    import java.io.FileReader;
    import java.io.IOException;
    
    public class ReadFileLineByLineUsingBufferedReader {
    
    	public static void main(String[] args) {
    		BufferedReader reader;
    		try {
    			reader = new BufferedReader(new FileReader(
    					"/Users/pankaj/Downloads/myfile.txt"));
    			String line = reader.readLine();
    			while (line != null) {
    				System.out.println(line);
    				// read next line
    				line = reader.readLine();
    			}
    			reader.close();
    		} catch (IOException e) {
    			e.printStackTrace();
    		}
    	}
    }

### Java使用Scanner逐行读取文件 **(****Java Read File line by line using Scanner****)** ###

We can use [Scanner][] class to open a file and then read its content line by line. Below is the scanner example to read file line by line and print it.

我们可以使用[Scanner][]类打开文件，然后逐行读取其内容。 以下是扫描仪示例，用于逐行读取文件并进行打印。

package com.journaldev.readfileslinebyline;
    
    import java.io.File;
    import java.io.FileNotFoundException;
    import java.util.Scanner;
    
    public class ReadFileLineByLineUsingScanner {
    
    	public static void main(String[] args) {
    		try {
    			Scanner scanner = new Scanner(new File("/Users/pankaj/Downloads/myfile.txt"));
    			while (scanner.hasNextLine()) {
    				System.out.println(scanner.nextLine());
    			}
    			scanner.close();
    		} catch (FileNotFoundException e) {
    			e.printStackTrace();
    		}
    	}
    
    }

### Java使用文件逐行读取文件 **(****Java Read File line by line using Files****)** ###

`java.nio.file.Files` is a utility class that contains various useful methods. Files `readAllLines` method can be used to read all the file lines into a [list][] of string.

`java.nio.file.Files`是一个实用程序类，其中包含各种有用的方法。 文件`readAllLines`方法可用于将所有文件行读入字符串[列表][list] 。

package com.journaldev.readfileslinebyline;
    
    import java.io.IOException;
    import java.nio.file.Files;
    import java.nio.file.Paths;
    import java.util.List;
    
    public class ReadFileLineByLineUsingFiles {
    
    	public static void main(String[] args) {
    		try {
    			List<String> allLines = Files.readAllLines(Paths.get("/Users/pankaj/Downloads/myfile.txt"));
    			for (String line : allLines) {
    				System.out.println(line);
    			}
    		} catch (IOException e) {
    			e.printStackTrace();
    		}
    	}
    
    }

### Java使用RandomAccessFile逐行读取文件 **(****Java Read File line by line using RandomAccessFile****)** ###

We can use `RandomAccessFile` to open a file in read mode and then use its `readLine` method to read file line by line.

我们可以使用`RandomAccessFile`以读取模式打开文件，然后使用其`readLine`方法逐行读取文件。

package com.journaldev.readfileslinebyline;
    
    import java.io.IOException;
    import java.io.RandomAccessFile;
    
    public class ReadFileLineByLineUsingRandomAccessFile {
    
    	public static void main(String[] args) {
    		try {
    			RandomAccessFile file = new RandomAccessFile("/Users/pankaj/Downloads/myfile.txt", "r");
    			String str;
    			while ((str = file.readLine()) != null) {
    				System.out.println(str);
    			}
    			file.close();
    		} catch (IOException e) {
    			e.printStackTrace();
    		}
    	}
    
    }

That’s all for java read file line by line using different methods.

这就是使用不同方法逐行读取Java文件的全部内容。

References:

参考文献：

*  [BufferedReader API Doc][]
    
    [BufferedReader API文档][BufferedReader API Doc]
 *  [Files API Doc][]
    
    [文件API文档][Files API Doc]

> 翻译自: [https://www.journaldev.com/709/java-read-file-line-by-line][https_www.journaldev.com_709_java-read-file-line-by-line]

java逐行读取文件

[Scanner]: https://www.journaldev.com/872/scanner-class-in-java
[list]: https://www.journaldev.com/11444/java-list
[BufferedReader API Doc]: https://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html#readLine%28%29
[Files API Doc]: https://docs.oracle.com/javase/8/docs/api/java/nio/file/Files.html#readAllLines-java.nio.file.Path-
[https_www.journaldev.com_709_java-read-file-line-by-line]: https://www.journaldev.com/709/java-read-file-line-by-line