public static void main(String[] args) throws UnknownHostException {
MongoClient client = new MongoClient();
DB database = client.getDB("school");
DBCollection collection = database.getCollection("students");
/*
Hint/spoiler: With the new schema, this problem is a lot harder
and that is sort of the point. One way is to find the lowest
homework in code and then update the scores array with the low
homework pruned. If you are struggling with the Node.js side of
this, look at the .slice() operator, which can remove an element
from an array in-place.
*/
DBCursor cursor = collection.find();
try {
while (cursor.hasNext()) {
BasicDBObject student = (BasicDBObject) cursor.next();
int studentId = student.getInt("_id");
String name = student.getString("name");
BasicDBList scores = (BasicDBList) student.get("scores");
System.out.printf("_id[%d], name[%s], scores%s %n", studentId, name, scores);
DBObject scoreToRemove = null;
double minScoreValue = 100.0;
for (Object obj : scores) {
BasicDBObject score = (BasicDBObject) obj;
String type = score.getString("type");
if (!"homework".equals(type)) {
continue;
}
double curScoreValue = score.getDouble("score");
System.out.printf("type[%s], current score value[%f] %n", type, curScoreValue);
if (curScoreValue < minScoreValue) {
scoreToRemove = score;
minScoreValue = curScoreValue;
}
}
System.out.printf("score to remove[%s] %n", scoreToRemove);
if (scoreToRemove != null) {
scores.remove(scoreToRemove);
BasicDBObject query = new BasicDBObject("_id", studentId);
BasicDBObject scoresUpdate =
new BasicDBObject("$set", new BasicDBObject("scores", scores));
WriteResult result = collection.update(query, scoresUpdate);
System.out.printf("update count[%d] %n", result.getN());
}
}
} finally {
cursor.close();
}
}
