cqc
ByteStreams and CharStreams
ByteStreams处理的是字节， 对应的是InputStream和OutputStream CharStreams处理的是字符， 对应的是Reader和Writer注意：Guava提供的流操作方法都不需要用户去close流
ByteStreams | CharStreams |
byte[] toByteArray(InputStream) | String toString(Readable) |
N/A | List<String> readLines(Readable) |
long copy(InputStream, OutputStream) | long copy(Readable, Appendable) |
void readFully(InputStream, byte[]) | N/A |
void skipFully(InputStream, long) | void skipFully(Reader, long) |
OutputStream nullOutputStream() | Writer nullWriter() |
Sources and sinks
Guava为读操作专门抽象出Source的概念，将不同的数据载体(如，File、URL)抽象成统一的操作方法，同样为写操作专门抽象出Sink的概念
Creating sources and sinks
Bytes | Chars |
Files.asByteSource(File) | Files.asCharSource(File, Charset) |
Files.asByteSink(File, FileWriteMode...) | Files.asCharSink(File, Charset, FileWriteMode...) |
Resources.asByteSource(URL) | Resources.asCharSource(URL, Charset) |
ByteSource.wrap(byte[]) | CharSource.wrap(CharSequence) |
ByteSource.concat(ByteSource...) | CharSource.concat(CharSource...) |
ByteSource.slice(long, long) | N/A |
N/A | ByteSource.asCharSource(Charset) |
N/A | ByteSink.asCharSink(Charset) |
Source operations
ByteSource | CharSource |
byte[] read() | String read() |
N/A | ImmutableList<String> readLines() |
N/A | String readFirstLine() |
long copyTo(ByteSink) | long copyTo(CharSink) |
long copyTo(OutputStream) | long copyTo(Appendable) |
long size() | long length() |
boolean isEmpty() | boolean isEmpty() |
boolean contentEquals(ByteSource) | N/A |
HashCode hash(HashFunction) | N/A |
Sink operations
ByteSink | CharSink |
void write(byte[]) | void write(CharSequence) |
long writeFrom(InputStream) | long writeFrom(Readable) |
N/A | void writeLines(Iterable<? extends CharSequence>) |
N/A | void writeLines(Iterable<? extends CharSequence>, String) |
// Read the lines of a UTF-8 text file
ImmutableList<String> lines = Files.asCharSource(file, Charsets.UTF_8)
.readLines();
// Count distinct word occurrences in a file
Multiset<String> wordOccurrences = HashMultiset.create(
Splitter.on(CharMatcher.WHITESPACE)
.trimResults()
.omitEmptyStrings()
.split(Files.asCharSource(file, Charsets.UTF_8).read()));
// SHA-1 a file
HashCode hash = Files.asByteSource(file).hash(Hashing.sha1());
// Copy the data from a URL to a file
Resources.asByteSource(url).copyTo(Files.asByteSink(file));
Files
Guava也提供了一个和JDK7上的类似Files工具类，但我看Guava提供的功能似乎更丰富些，以下为官方提供的几个方法
Method | Description |
createParentDirs(File) | Creates necessary but nonexistent parent directories of the file. |
getFileExtension(String) | Gets the file extension of the file described by the path. |
getNameWithoutExtension(String) | Gets the name of the file with its extension removed |
simplifyPath(String) | Cleans up the path. Not always consistent with your filesystem; test carefully! |
fileTreeTraverser() | Returns a TreeTraverser that can traverse file trees |