Keep Coding

The following is my code:
HttpPost postRequest = new HttpPost("http://localhost:8983/solr/core1/update/json?wt=json&commit=true");
StringEntity entity = new StringEntity("{\n"
+ " \"id\": \"1\",\n"
+ " \"title\": \"Doc 1\"\n"
+ "}", "UTF-8");
entity.setContentType("application/json");
postRequest.setEntity(entity);
HttpResponse response = httpClient.execute(postRequest);
when i am trying to add json to solr 5.5.0 , i got the below exception:
{"responseHeader":{"status":400,"QTime":2},"error":{"metadata":["error-class","org.apache.solr.common.SolrException","root-error-class","org.apache.solr.common.SolrException"],"msg":"Unknown command 'id' at [9]","code":400}}
Can anyone please help me???