Program: 93652
Project: 93652
Buggy source:
@Override public void handleRequest(HttpServerExchange exchange,RequestContext context) throws Exception {
  if (context.getMethod() == RequestContext.METHOD.GET || context.getMethod() == RequestContext.METHOD.DELETE) {
    next.handleRequest(exchange,context);
    return;
  }
  HeaderValues contentTypes=exchange.getRequestHeaders().get(Headers.CONTENT_TYPE);
  if (contentTypes == null || contentTypes.isEmpty() || contentTypes.stream().noneMatch(ct -> ct.startsWith(Representation.HAL_JSON_MEDIA_TYPE) || ct.startsWith(JSON_MEDIA_TYPE))) {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_UNSUPPORTED_MEDIA_TYPE,"String_Node_Str" + Representation.HAL_JSON_MEDIA_TYPE + "String_Node_Str"+ JSON_MEDIA_TYPE);
    return;
  }
  String _content=ChannelReader.read(exchange.getRequestChannel());
  DBObject content;
  try {
    content=(DBObject)JSON.parse(_content);
  }
 catch (  JSONParseException ex) {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_NOT_ACCEPTABLE,"String_Node_Str",ex);
    return;
  }
  HashSet<String> keysToRemove=new HashSet<>();
  if (content == null) {
    context.setContent(null);
  }
 else {
    content.keySet().stream().filter((key) -> (key.startsWith("String_Node_Str"))).forEach((key) -> {
      keysToRemove.add(key);
    }
);
    keysToRemove.stream().map((keyToRemove) -> {
      content.removeField(keyToRemove);
      return keyToRemove;
    }
).forEach((keyToRemove) -> {
      context.addWarning("String_Node_Str" + keyToRemove + "String_Node_Str");
    }
);
    context.setContent(content);
  }
  next.handleRequest(exchange,context);
}

Fixed version (ground truth):
@Override public void handleRequest(HttpServerExchange exchange,RequestContext context) throws Exception {
  if (context.getMethod() == RequestContext.METHOD.GET || context.getMethod() == RequestContext.METHOD.DELETE) {
    next.handleRequest(exchange,context);
    return;
  }
  HeaderValues contentTypes=exchange.getRequestHeaders().get(Headers.CONTENT_TYPE);
  if (contentTypes == null || contentTypes.isEmpty() || contentTypes.stream().noneMatch(ct -> ct.startsWith(Representation.HAL_JSON_MEDIA_TYPE) || ct.startsWith(JSON_MEDIA_TYPE))) {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_UNSUPPORTED_MEDIA_TYPE,"String_Node_Str" + Representation.HAL_JSON_MEDIA_TYPE + "String_Node_Str"+ JSON_MEDIA_TYPE);
    return;
  }
  String _content=ChannelReader.read(exchange.getRequestChannel());
  DBObject content;
  try {
    content=(DBObject)JSON.parse(_content);
  }
 catch (  JSONParseException ex) {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_NOT_ACCEPTABLE,"String_Node_Str",ex);
    return;
  }
  HashSet<String> keysToRemove=new HashSet<>();
  if (content == null) {
    context.setContent(null);
  }
 else {
    content.keySet().stream().filter((key) -> (key.startsWith("String_Node_Str") && !key.equals("String_Node_Str"))).forEach((key) -> {
      keysToRemove.add(key);
    }
);
    keysToRemove.stream().map((keyToRemove) -> {
      content.removeField(keyToRemove);
      return keyToRemove;
    }
).forEach((keyToRemove) -> {
      context.addWarning("String_Node_Str" + keyToRemove + "String_Node_Str");
    }
);
    context.setContent(content);
  }
  next.handleRequest(exchange,context);
}