如果您使用的是AWS SDK v2，请调用IoUtils.toUtf8String（）：

public String convertStreamToString(InputStream is) {
    return IoUtils.toUtf8String(is);
}

这个很好，因为：

它可以安全地处理Charset。您可以控制读取缓冲区的大小。您可以设置生成器的长度，而不必是精确的值。不受库依赖关系的影响。适用于Java 7或更高版本。

怎么做？

public static String convertStreamToString(InputStream is) throws IOException {
   StringBuilder sb = new StringBuilder(2048); // Define a size if you have an idea of it.
   char[] read = new char[128]; // Your buffer size.
   try (InputStreamReader ir = new InputStreamReader(is, StandardCharsets.UTF_8)) {
     for (int i; -1 != (i = ir.read(read)); sb.append(read, 0, i));
   }
   return sb.toString();
}

对于JDK 9

public static String inputStreamString(InputStream inputStream) throws IOException {
    try (inputStream) {
        return new String(inputStream.readAllBytes(), StandardCharsets.UTF_8);
    }
}

这是一个改编自org.apache.commons.io.IOUtils源代码的答案，适用于那些想要apache实现但不想要整个库的人。

private static final int BUFFER_SIZE = 4 * 1024;

public static String inputStreamToString(InputStream inputStream, String charsetName)
        throws IOException {
    StringBuilder builder = new StringBuilder();
    InputStreamReader reader = new InputStreamReader(inputStream, charsetName);
    char[] buffer = new char[BUFFER_SIZE];
    int length;
    while ((length = reader.read(buffer)) != -1) {
        builder.append(buffer, 0, length);
    }
    return builder.toString();
}

此代码适用于新的Java学习者：

private String textDataFromFile;

public String getFromFile(InputStream myInputStream) throws FileNotFoundException, IOException {

    BufferedReader bufferReader = new BufferedReader(new InputStreamReader(myInputStream));

    StringBuilder stringBuilder = new StringBuilder();

    String eachStringLine;

    while ((eachStringLine = bufferReader.readLine()) != null) {
        stringBuilder.append(eachStringLine).append("\n");
    }
    textDataFromFile = stringBuilder.toString();

    return textDataFromFile;
}

InputStream  inputStream = null;
BufferedReader bufferedReader = null;
try {
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
    String stringBuilder = new StringBuilder();
    String content;
    while((content = bufferedReader.readLine()) != null){
        stringBuilder.append(content);
    }
    System.out.println("content of file::" + stringBuilder.toString());
}
catch (IOException e) {
            e.printStackTrace();
        }finally{           
            if(bufferedReader != null){
                try{
                    bufferedReader.close();
                }catch(IoException ex){
                   ex.printStackTrace();
            }

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();
}