Files

guava源码：Files

看一下它的调用过程

 public static <T> T readLines(File file, Charset charset, LineProcessor<T> callback) throws IOException { return asCharSource(file, charset).readLines(callback); } 

  asCharSource->asByteSource->FileByteSource

FileByteSource里 是用的FIleInputStream

 @Override
public FileInputStream openStream() throws IOException { return new FileInputStream(file); } 

在asByteSource里 对FIleByteSource转换 成BufferedReader

 public static BufferedReader newReader(File file, Charset charset) throws FileNotFoundException { checkNotNull(file); checkNotNull(charset); return new BufferedReader( new InputStreamReader(new FileInputStream(file), charset)); } 

在ReadLines中

 public static <T> T readLines( Readable readable, LineProcessor<T> processor) throws IOException { checkNotNull(readable); checkNotNull(processor); LineReader lineReader = new LineReader(readable); String line; while ((line = lineReader.readLine()) != null) { if (!processor.processLine(line)) { break; } } return processor.getResult(); }