# Java 將文件讀取為字符串（已針對 Java 8 更新） > 原文： [https://howtodoinjava.com/java/io/java-read-file-to-string-examples/](https://howtodoinjava.com/java/io/java-read-file-to-string-examples/) 學習**將文件讀取為 Java 中的字符串**。 給定的示例使用`Files.readAllBytes()`，`Files.lines()`（以**逐行讀取**）和`FileReader`和`BufferedReader`至**將文本文件讀取為字符串**。 ## 將文件讀取為字符串的 3 個 Java 示例 用于將文件讀入字符串的所有 3 個示例的源代碼。 ```java //Java 8 - Read file line by line - Files.lines(Path path, Charset cs) private static String readLineByLineJava8(String filePath) { StringBuilder contentBuilder = new StringBuilder(); try (Stream<String> stream = Files.lines( Paths.get(filePath), StandardCharsets.UTF_8)) { stream.forEach(s -> contentBuilder.append(s).append("\n")); } catch (IOException e) { e.printStackTrace(); } return contentBuilder.toString(); } //Files.readAllBytes(Path path) - Java 7 and above private static String readAllBytesJava7(String filePath) { String content = ""; try { content = new String ( Files.readAllBytes( Paths.get(filePath) ) ); } catch (IOException e) { e.printStackTrace(); } return content; } //Using BufferedReader and FileReader - Below Java 7 private static String usingBufferedReader(String filePath) { StringBuilder contentBuilder = new StringBuilder(); try (BufferedReader br = new BufferedReader(new FileReader(filePath))) { String sCurrentLine; while ((sCurrentLine = br.readLine()) != null) { contentBuilder.append(sCurrentLine).append("\n"); } } catch (IOException e) { e.printStackTrace(); } return contentBuilder.toString(); } ``` 我已將文件`data.txt`放置在位置`c:/temp`。 我將在所有 3 個示例中閱讀此文件。 ```java Welcome to howtodoinjava.com blog. Learn to grow. ``` ## `Files.lines()` – 在 Java 8 中將文件讀取為字符串 [`lines()`](https://docs.oracle.com/javase/8/docs/api/java/nio/file/Files.html#lines-java.nio.file.Path-java.nio.charset.Charset-)方法**從文件中讀取所有行以流**，并隨著[流](//howtodoinjava.com/java8/java-8-tutorial-streams-by-examples/)被消耗而懶惰地填充。 使用指定的字符集將文件中的字節解碼為字符。 ```java import java.io.IOException; import java.nio.charset.StandardCharsets; import java.nio.file.Files; import java.nio.file.Paths; import java.util.stream.Stream; public class ReadFileToString { public static void main(String[] args) { String filePath = "c:/temp/data.txt"; System.out.println( readLineByLineJava8( filePath ) ); } //Read file content into string with - Files.lines(Path path, Charset cs) private static String readLineByLineJava8(String filePath) { StringBuilder contentBuilder = new StringBuilder(); try (Stream<String> stream = Files.lines( Paths.get(filePath), StandardCharsets.UTF_8)) { stream.forEach(s -> contentBuilder.append(s).append("\n")); } catch (IOException e) { e.printStackTrace(); } return contentBuilder.toString(); } } ``` 輸出： ```java Welcome to howtodoinjava.com blog. Learn to grow. ``` ## 將整個文件讀到字符串 – `Files.readAllBytes()`（≥ Java 7） [`readAllBytes()`](https://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#readAllBytes(java.nio.file.Path))方法*從文件*讀取所有字節。 該方法可確保在讀取所有字節或引發 I/O 錯誤或其他運行時異常時關閉文件。 讀取所有字節后，我們將這些字節傳遞給`String`類構造器以創建一個字符串。 ```java import java.io.IOException; import java.nio.file.Files; import java.nio.file.Paths; public class ReadFileToString { public static void main(String[] args) { String filePath = "c:/temp/data.txt"; System.out.println( readAllBytesJava7( filePath ) ); } //Read file content into string with - Files.readAllBytes(Path path) private static String readAllBytesJava7(String filePath) { String content = ""; try { content = new String ( Files.readAllBytes( Paths.get(filePath) ) ); } catch (IOException e) { e.printStackTrace(); } return content; } } ``` 輸出： ```java Welcome to howtodoinjava.com blog. Learn to grow. ``` ## 逐行讀取文件 – `BufferedReader`（< Java 7） 如果仍不使用 Java 7 或更高版本，則使用[`BufferedReader`](https://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html)類。 `readLine()`方法**一次讀取一行文件**，然后返回內容。 ```java import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; public class ReadFileToString { public static void main(String[] args) { String filePath = "c:/temp/data.txt"; System.out.println( usingBufferedReader( filePath ) ); } //Read file content into string with - using BufferedReader and FileReader //You can use this if you are still not using Java 8 private static String usingBufferedReader(String filePath) { StringBuilder contentBuilder = new StringBuilder(); try (BufferedReader br = new BufferedReader(new FileReader(filePath))) { String sCurrentLine; while ((sCurrentLine = br.readLine()) != null) { contentBuilder.append(sCurrentLine).append("\n"); } } catch (IOException e) { e.printStackTrace(); } return contentBuilder.toString(); } } ``` 輸出： ```java Welcome to howtodoinjava.com blog. Learn to grow. ``` 使用上述任何一種方法，都可以使用 Java 將文件**讀入字符串**。 學習愉快！