code: public static  PrivateKey loadPrivateKey(File file) { 
      	FileInputStream inputStream = null;
      	try {
      		inputStream = new FileInputStream(file);			
      		return loadPrivateKey(inputStream);
  		} catch (FileNotFoundException e) {
  			throw new RuntimeException("文件不存在");
  		}finally {
  			try {inputStream.close();} catch (Exception e2) {}
  		}
      }
docs: 从文件中加载私钥
  @param file 私钥文件