Force REST API - giving below exception

[sagarjamage7714]

java.lang.RuntimeException: com.fasterxml.jackson.databind.JsonMappingException: No content to map due to end-of-input
at [Source: UNKNOWN; line: 1, column: 1]
java.lang.RuntimeException: com.fasterxml.jackson.databind.JsonMappingException: No content to map due to end-of-input
at [Source: UNKNOWN; line: 1, column: 1]
at com.force.api.Auth.oauthLoginPasswordFlow(Auth.java:47)
at com.force.api.Auth.authenticate(Auth.java:208)
at com.force.api.ForceApi.(ForceApi.java:68)
at com.aws.datasync.SalesforceConnector.main(SalesforceConnector.java:23)
Caused by: com.fasterxml.jackson.databind.JsonMappingException: No content to map due to end-of-input
at [Source: UNKNOWN; line: 1, column: 1]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:148)
at com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:3607)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3547)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2648)
at com.force.api.Auth.oauthLoginPasswordFlow(Auth.java:32)
... 3 more