Java中InputStream和String之间的转化

　　在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.

一、InputStream转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.

二、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());

　　

转载:https://blog.csdn.net/lmy86263/article/details/60479350