Java中InputStream和String之间的转换方法

3/8/2017来源:ASP.NET技巧人气:1983

java中InputStream和String之间的转化十分普遍,本文主要是总结一下转换的各种方法,包括JDK原生提供的,还有一些外部依赖提供的。

1、InputStream转化为String

1.1 JDK原生提供

方法一: byte[] bytes = new byte[0]; bytes = new byte[inputStream.available()]; inputStream.read(bytes); String str = new String(bytes); 方法二: String result = new BufferedReader(new InputStreamReader(inputStream)) .lines().collect(Collectors.joining(System.lineSeparator())); 方法三: String result = new BufferedReader(new InputStreamReader(inputStream)) .lines().parallel().collect(Collectors.joining(System.lineSeparator())); 方法四: Scanner s = new Scanner(inputStream).useDelimiter("\\A"); String str = s.hasNext() ? s.next() : ""; 方法五: String resource = new Scanner(inputStream).useDelimiter("\\Z").next(); return resource; 方法六: StringBuilder sb = new StringBuilder(); String line; BufferedReader br = new BufferedReader(new InputStreamReader(inputStream)); while ((line = br.readLine()) != null) { sb.append(line); } String str = sb.toString(); return str; 方法七: ByteArrayOutputStream result = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int length; while ((length = inputStream.read(buffer)) != -1) { result.write(buffer, 0, length); } String str = result.toString(StandardCharsets.UTF_8.name()); return str; 方法八: BufferedInputStream bis = new BufferedInputStream(inputStream); ByteArrayOutputStream buf = new ByteArrayOutputStream(); int result = bis.read(); while(result != -1) { buf.write((byte) result); result = bis.read(); } String str = buf.toString(); return str;

1.2 Apache Common提供

方法九: StringWriter writer = new StringWriter(); IOUtils.copy(inputStream, writer, StandardCharsets.UTF_8.name()); String str = writer.toString(); 方法十: String str = IOUtils.toString(inputStream, "utf-8");

1.3 Google Guava提供

方法十一: String str = CharStreams.toString(new InputStreamReader(inputStream, StandardCharsets.UTF_8)); 方法十二: String str = new String(ByteStreams.toByteArray(inputStream));

针对一个2MB的文件的输入流,多次执行测试如下(单位是毫秒):

方法十: 111 方法十一: 236 方法十二: 36 方法一: 36 方法二: 87 方法三: 66 方法四: 101 方法五: 178 方法六: 40 方法七: 21 方法八: 107 方法九: 31

从上述结果来看,方法七和方法九更好一些,而方法五和方法十一会更差一些。

2、String转化为InputStream

2.1 JDK原生提供

InputStream is = new ByteArrayInputStream(str.getBytes());

2.2 Apache Common提供

InputStream targetStream = IOUtils.toInputStream(str, StandardCharsets.UTF_8.name());

2.3 Google Guava提供

InputStream targetStream = new ReaderInputStream(CharSource.wrap(str).openStream(), StandardCharsets.UTF_8.name());