InputStream String2InputStream(String str){
 ByteArrayInputStream stream = new ByteArrayInputStream(str.getBytes());
 return stream;
}

String inputStream2String(InputStream is){
 BufferedReader in = new BufferedReader(new InputStreamReader(is));
 StringBuffer buffer = new StringBuffer();
 String line = "";
 while ((line = in.readLine()) != null){
  buffer.append(line);
 }
 return buffer.toString();
}

String all_content=null;
  try {
  all_content =new String();

   InputStream ins = 获取的输入流;

   ByteArrayOutputStream outputstream = new ByteArrayOutputStream();
  byte[] str_b = new byte[1024];
  int i = -1;
  while ((i=ins.read(str_b)) > 0) {
   outputstream.write(str_b,0,i);
  }
  all_content = outputstream.toString();
 } catch (Exception e) {

e.printStackTrace();
  }

InputStream in = new InputStream(new FileInputStream(File));

public void inputstreamtofile(InputStream ins,File file){
OutputStream os = new FileOutputStream(file);
int bytesRead = 0;
byte[] buffer = new byte[8192];
while ((bytesRead = ins.read(buffer, 0, 8192)) != -1) {
os.write(buffer, 0, bytesRead);
}
os.close();
ins.close();
}