how to query data using mongo in java

To query data using MongoDB in Java, you can use the following steps:

1. Create a MongoClient instance to connect to the MongoDB server.

MongoClient mongoClient = new MongoClient("localhost", 27017);

2. Get a reference to the database you want to query.

MongoDatabase database = mongoClient.getDatabase("mydb");

3. Get a reference to the collection you want to query.

MongoCollection<Document> collection = database.getCollection("mycollection");

4. Build a query using the QueryBuilder class.

QueryBuilder queryBuilder = QueryBuilder.start("name").is("John");

5. Execute the query on the collection.

FindIterable<Document> result = collection.find(queryBuilder.get());

6. Iterate over the result set to retrieve the data.

for (Document doc : result) {
    System.out.println(doc.toJson());
}

Note: This code requires the MongoDB Java driver to be installed in your project.