try {
  File f = new File("filename.txt");
  Scanner r = new Scanner(f);  
  while (r.hasNextLine()) {
    String data = r.nextLine();
    JOptionPane.showMessageDialog(data);
  }
  r.close();
} catch (FileNotFoundException ex) {
  JOptionPane.showMessageDialog("Error occurred");
  ex.printStackTrace();
}

你想怎么处理这篇文章?文件是否小到可以装入内存?我会尽量找到最简单的方法来处理您需要的文件。FileUtils库可以很好地处理这个问题。

for(String line: FileUtils.readLines("my-text-file"))
    System.out.println(line);

Guava提供了一个简单的例子:

import com.google.common.base.Charsets;
import com.google.common.io.Files;

String contents = Files.toString(filePath, Charsets.UTF_8);

我记录了15种用Java读取文件的方法，然后测试了它们在不同文件大小下的速度——从1kb到1gb，下面是最常用的三种方法:

java.nio.file.Files.readAllBytes() Tested to work in Java 7, 8, and 9. import java.io.File; import java.io.IOException; import java.nio.file.Files; public class ReadFile_Files_ReadAllBytes { public static void main(String [] pArgs) throws IOException { String fileName = "c:\\temp\\sample-10KB.txt"; File file = new File(fileName); byte [] fileBytes = Files.readAllBytes(file.toPath()); char singleChar; for(byte b : fileBytes) { singleChar = (char) b; System.out.print(singleChar); } } } java.io.BufferedReader.readLine() Tested to work in Java 7, 8, 9. import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; public class ReadFile_BufferedReader_ReadLine { public static void main(String [] args) throws IOException { String fileName = "c:\\temp\\sample-10KB.txt"; FileReader fileReader = new FileReader(fileName); try (BufferedReader bufferedReader = new BufferedReader(fileReader)) { String line; while((line = bufferedReader.readLine()) != null) { System.out.println(line); } } } } java.nio.file.Files.lines() This was tested to work in Java 8 and 9 but won't work in Java 7 because of the lambda expression requirement. import java.io.File; import java.io.IOException; import java.nio.file.Files; import java.util.stream.Stream; public class ReadFile_Files_Lines { public static void main(String[] pArgs) throws IOException { String fileName = "c:\\temp\\sample-10KB.txt"; File file = new File(fileName); try (Stream linesStream = Files.lines(file.toPath())) { linesStream.forEach(line -> { System.out.println(line); }); } } }

对于基于jsf的Maven web应用程序，只需使用ClassLoader和Resources文件夹读取任何你想要的文件:

Put any file you want to read in the Resources folder. Put the Apache Commons IO dependency into your POM: <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-io</artifactId> <version>1.3.2</version> </dependency> Use the code below to read it (e.g. below is reading in a .json file): String metadata = null; FileInputStream inputStream; try { ClassLoader loader = Thread.currentThread().getContextClassLoader(); inputStream = (FileInputStream) loader .getResourceAsStream("/metadata.json"); metadata = IOUtils.toString(inputStream); inputStream.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return metadata;

您可以对文本文件、.properties文件、XSD模式等执行相同的操作。

org.apache.commons.io.FileUtils中的方法也可能非常方便，例如:

/**
 * Reads the contents of a file line by line to a List
 * of Strings using the default encoding for the VM.
 */
static List readLines(File file)