将inputStream转换为字符串的方法

public static String getStringFromInputStream(InputStream inputStream) {

    BufferedReader bufferedReader = null;
    StringBuilder stringBuilder = new StringBuilder();
    String line;

    try {
        bufferedReader = new BufferedReader(new InputStreamReader(
                inputStream));
        while ((line = bufferedReader.readLine()) != null) {
            stringBuilder.append(line);
        }
    } catch (IOException e) {
        logger.error(e.getMessage());
    } finally {
        if (bufferedReader != null) {
            try {
                bufferedReader.close();
            } catch (IOException e) {
                logger.error(e.getMessage());
            }
        }
    }
    return stringBuilder.toString();
}

就reduce和concat而言，它可以在Java 8中表示为：

String fromFile = new BufferedReader(new   
InputStreamReader(inputStream)).lines().reduce(String::concat).get();

  InputStream IS=new URL("http://www.petrol.si/api/gas_prices.json").openStream();   

  ByteArrayOutputStream BAOS=new ByteArrayOutputStream();
  IOUtils.copy(IS, BAOS);
  String d= new String(BAOS.toByteArray(),"UTF-8");           

System.out.println(d);

这里或多或少有sampath的答案，清理了一点并表示为函数：

String streamToString(InputStream in) throws IOException {
  StringBuilder out = new StringBuilder();
  BufferedReader br = new BufferedReader(new InputStreamReader(in));
  for(String line = br.readLine(); line != null; line = br.readLine()) 
    out.append(line);
  br.close();
  return out.toString();
}

JDK中最简单的方法是使用以下代码片段。

String convertToString(InputStream in){
    String resource = new Scanner(in).useDelimiter("\\Z").next();
    return resource;
}

以下是我经过一些实验后提出的最优雅、纯Java（无库）解决方案：

public static String fromStream(InputStream in) throws IOException
{
    BufferedReader reader = new BufferedReader(new InputStreamReader(in));
    StringBuilder out = new StringBuilder();
    String newLine = System.getProperty("line.separator");
    String line;
    while ((line = reader.readLine()) != null) {
        out.append(line);
        out.append(newLine);
    }
    return out.toString();
}