While integrating update document API getting this error - https://dash.readme.com/api/v1/api-specification/{id}

In java code encoding and decoding working fine but when passing encoded string in request getting this error

{
"error": "SPEC_INVALID",
"message": "The spec you uploaded isn't a valid JSON or YAML file. Here's the error we found:\n\nNot valid YAML",
"suggestion": "Try running your spec through a validator to see if they pick up any issues with the formatting!",

"poem": [
"When we asked for your swagger",
"It seems you misunderstood.",
"You sent us a cool attitude.",
"Instead some JSON would have been good."
]
}