总结其他答案,我发现了11种主要方法(请参见下文)。我编写了一些性能测试(请参见下面的结果):
将InputStream转换为字符串的方法:
使用IOUtils.toString
(Apache Utils)
String result = IOUtils.toString(inputStream, StandardCharsets.UTF_8);
使用CharStreams
(番石榴)
String result = CharStreams.toString(new InputStreamReader(
inputStream, Charsets.UTF_8));
使用Scanner
(JDK)
Scanner s = new Scanner(inputStream).useDelimiter("\\A");
String result = s.hasNext() ? s.next() : "";
使用Stream API(Java 8)。警告:此解决方案会将不同的换行符(如\r\n
)转换为\n
。
String result = new BufferedReader(new InputStreamReader(inputStream))
.lines().collect(Collectors.joining("\n"));
使用并行流API(Java 8)。警告:此解决方案会将不同的换行符(如\r\n
)转换为\n
。
String result = new BufferedReader(new InputStreamReader(inputStream)).lines()
.parallel().collect(Collectors.joining("\n"));
使用InputStreamReader
和StringBuilder
(JDK)
final int bufferSize = 1024;
final char[] buffer = new char[bufferSize];
final StringBuilder out = new StringBuilder();
Reader in = new InputStreamReader(stream, StandardCharsets.UTF_8);
int charsRead;
while((charsRead = in.read(buffer, 0, buffer.length)) > 0) {
out.append(buffer, 0, charsRead);
}
return out.toString();
使用StringWriter
和IOUtils.copy
(Apache Commons)
StringWriter writer = new StringWriter();
IOUtils.copy(inputStream, writer, "UTF-8");
return writer.toString();
使用ByteArrayOutputStream
和inputStream.read
(JDK)
ByteArrayOutputStream result = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int length;
while ((length = inputStream.read(buffer)) != -1) {
result.write(buffer, 0, length);
}
// StandardCharsets.UTF_8.name() > JDK 7
return result.toString("UTF-8");
使用BufferedReader
(JDK)。警告:此解决方案将不同的换行符(如\n\r
)转换为line.separator
系统属性(例如,在Windows中转换为“ \ r \ n”)。
String newLine = System.getProperty("line.separator");
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
StringBuilder result = new StringBuilder();
boolean flag = false;
for (String line; (line = reader.readLine()) != null; ) {
result.append(flag? newLine: "").append(line);
flag = true;
}
return result.toString();
使用BufferedInputStream
和ByteArrayOutputStream
(JDK)
BufferedInputStream bis = new BufferedInputStream(inputStream);
ByteArrayOutputStream buf = new ByteArrayOutputStream();
int result = bis.read();
while(result != -1) {
buf.write((byte) result);
result = bis.read();
}
// StandardCharsets.UTF_8.name() > JDK 7
return buf.toString("UTF-8");
使用inputStream.read()
和StringBuilder
(JDK)。警告:此解决方案存在Unicode问题,例如俄语文本(仅适用于非Unicode文本)
int ch;
StringBuilder sb = new StringBuilder();
while((ch = inputStream.read()) != -1)
sb.append((char)ch);
reset();
return sb.toString();
警告:
解决方案4、5和9将不同的换行符转换为1。
解决方案11不能正确处理Unicode文本
性能测试
针对小型String
(长度= 175),github中 url的性能测试(模式=平均时间,系统= Linux,满分1,343分是最好的):
Benchmark Mode Cnt Score Error Units
8. ByteArrayOutputStream and read (JDK) avgt 10 1,343 ± 0,028 us/op
6. InputStreamReader and StringBuilder (JDK) avgt 10 6,980 ± 0,404 us/op
10. BufferedInputStream, ByteArrayOutputStream avgt 10 7,437 ± 0,735 us/op
11. InputStream.read() and StringBuilder (JDK) avgt 10 8,977 ± 0,328 us/op
7. StringWriter and IOUtils.copy (Apache) avgt 10 10,613 ± 0,599 us/op
1. IOUtils.toString (Apache Utils) avgt 10 10,605 ± 0,527 us/op
3. Scanner (JDK) avgt 10 12,083 ± 0,293 us/op
2. CharStreams (guava) avgt 10 12,999 ± 0,514 us/op
4. Stream Api (Java 8) avgt 10 15,811 ± 0,605 us/op
9. BufferedReader (JDK) avgt 10 16,038 ± 0,711 us/op
5. parallel Stream Api (Java 8) avgt 10 21,544 ± 0,583 us/op
针对大型String
(长度= 50100),github中的 url的性能测试(模式=平均时间,系统= Linux,得分200,715是最好的):
Benchmark Mode Cnt Score Error Units
8. ByteArrayOutputStream and read (JDK) avgt 10 200,715 ± 18,103 us/op
1. IOUtils.toString (Apache Utils) avgt 10 300,019 ± 8,751 us/op
6. InputStreamReader and StringBuilder (JDK) avgt 10 347,616 ± 130,348 us/op
7. StringWriter and IOUtils.copy (Apache) avgt 10 352,791 ± 105,337 us/op
2. CharStreams (guava) avgt 10 420,137 ± 59,877 us/op
9. BufferedReader (JDK) avgt 10 632,028 ± 17,002 us/op
5. parallel Stream Api (Java 8) avgt 10 662,999 ± 46,199 us/op
4. Stream Api (Java 8) avgt 10 701,269 ± 82,296 us/op
10. BufferedInputStream, ByteArrayOutputStream avgt 10 740,837 ± 5,613 us/op
3. Scanner (JDK) avgt 10 751,417 ± 62,026 us/op
11. InputStream.read() and StringBuilder (JDK) avgt 10 2919,350 ± 1101,942 us/op
图形(性能测试取决于Windows 7系统中的输入流长度)
性能测试(平均时间)取决于Windows 7系统中的输入流长度:
length 182 546 1092 3276 9828 29484 58968
test8 0.38 0.938 1.868 4.448 13.412 36.459 72.708
test4 2.362 3.609 5.573 12.769 40.74 81.415 159.864
test5 3.881 5.075 6.904 14.123 50.258 129.937 166.162
test9 2.237 3.493 5.422 11.977 45.98 89.336 177.39
test6 1.261 2.12 4.38 10.698 31.821 86.106 186.636
test7 1.601 2.391 3.646 8.367 38.196 110.221 211.016
test1 1.529 2.381 3.527 8.411 40.551 105.16 212.573
test3 3.035 3.934 8.606 20.858 61.571 118.744 235.428
test2 3.136 6.238 10.508 33.48 43.532 118.044 239.481
test10 1.593 4.736 7.527 20.557 59.856 162.907 323.147
test11 3.913 11.506 23.26 68.644 207.591 600.444 1211.545