Dinesh on Java

db.collection.update( <query>, <update>, <options> )

BasicDBObject newDocument = new BasicDBObject();
newDocument.put("empId", 10006);
newDocument.put("empName", "Dinesh Rajput");
newDocument.put("salary", 70000);
 
collection.update(new BasicDBObject().append("empId", 10006), newDocument);

2. This example show the use of “$inc” modifier to increase a particular value.
Find empId = 10006, update the “salary” value by increasing its value from 70000 to 90000, (70000 + 20000) = 90000.

BasicDBObject newDocument = new BasicDBObject().append("$inc", 
new BasicDBObject().append("salary", 20000));
 
collection.update(new BasicDBObject().append("empId", 10006), newDocument);

3. This example show the use of “$set” modifier to update a particular value.
Find empId = 10006, update the “salary” from 70000 to 90000.

BasicDBObject newDocument = new BasicDBObject().append("$set", 
 new BasicDBObject().append("salary", 90000));
 
collection.update(new BasicDBObject().append("empId", 10006), newDocument);

4. This example show the use of “multi” parameter to update a set of matched documents.
Find empAge= 26, update all the matched documents, “salary” value to 60000.

//find empAge= 26 , update all matched documents , "salary" value to 60000
BasicDBObject updateQuery = new BasicDBObject().append("$set", 
 new BasicDBObject().append("salary", "60000"));
 
//both methods are doing the same thing.
//collection.updateMulti(new BasicDBObject().append("empAge", "26"), updateQuery);
collection.update(new BasicDBObject().append("empAge", "26"), updateQuery, false, true);

See the full example and its output.

package com.dineshonjava.mongo.test;

import java.net.UnknownHostException;

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.Mongo;
import com.mongodb.MongoException;

/**
 * @author Dinesh Rajput
 *
 */
public class UpdateDocumentDemo {

 public static void printAllDocuments(DBCollection collection){
  DBCursor cursor = collection.find();
  while (cursor.hasNext()) {
   System.out.println(cursor.next());
  }
 }
 
 public static void removeAllDocuments(DBCollection collection){
  collection.remove(new BasicDBObject());
 }
 
 public static void insertDummyDocuments(DBCollection collection){
  BasicDBObject document = new BasicDBObject();
  document.put("empId", "10006");
  document.put("empName", "Dinesh");
  document.put("salary", 70000);
 
  BasicDBObject document2 = new BasicDBObject();
  document2.put("empId", "10007");
  document2.put("empName", "Sweety");
  document2.put("salary", 70000);
 
  BasicDBObject document3 = new BasicDBObject();
  document3.put("empId", "10008");
  document3.put("empName", "Dinesh");
  document3.put("salary", 60000);
 
  collection.insert(document);
  collection.insert(document2);
  collection.insert(document3);
 }
 
 public static void main(String[] args) {
 
 try {
 
  Mongo mongo = new Mongo("localhost", 27017);
  DB db = mongo.getDB("dineshonjavaDB");
 
  // get a single collection
  DBCollection collection = db.getCollection("employee");
 
  System.out.println("Testing 1...");
  insertDummyDocuments(collection);
  //find empId = 10006, and update it with new document
  BasicDBObject newDocument = new BasicDBObject();
  newDocument.put("empId", "10006");
  newDocument.put("empName", "Dinesh Rajput");
  newDocument.put("salary", 80000);
 
  collection.update(new BasicDBObject().append("empId", "10006"), newDocument);
 
  printAllDocuments(collection);
  removeAllDocuments(collection);
 
  System.out.println("Testing 2...");
  insertDummyDocuments(collection);
  //find empId = 10006 and increase its "salary" value by 90000
  BasicDBObject newDocument2 = new BasicDBObject().append("$inc", 
    new BasicDBObject().append("salary", 20000));
 
  collection.update(new BasicDBObject().append("empId", "10006"), newDocument2);
 
  printAllDocuments(collection);
  removeAllDocuments(collection);
 
  System.out.println("Testing 3...");
  insertDummyDocuments(collection);
  //find empId = 10006 and update salary to from 70000 to 90000
  BasicDBObject newDocument3 = new BasicDBObject().append("$set", 
    new BasicDBObject().append("salary", 90000));
 
  collection.update(new BasicDBObject().append("empId", "10006"), newDocument3);
  printAllDocuments(collection);
  removeAllDocuments(collection);
 
  System.out.println("Testing 4...");
  insertDummyDocuments(collection);
  //find empName = Dinesh , update all matched documents , salary value to 80000
  BasicDBObject updateQuery = new BasicDBObject().append("$set", 
    new BasicDBObject().append("salary", 80000));
 
  //both method are same
  //collection.updateMulti(new BasicDBObject().append("empName", "Dinesh"), updateQuery);
 
  collection.update(new BasicDBObject().append("empName", "Dinesh"), updateQuery, false, true);
 
  printAllDocuments(collection);
  removeAllDocuments(collection);
 
  System.out.println("Done");
 
  } catch (UnknownHostException e) {
   e.printStackTrace();
  } catch (MongoException e) {
   e.printStackTrace();
  }
 
 }

}

if every thing fine then run as java application and see the follwing output on the console.

References

1. How to do updating in MongoDB
2. Update modifiers operations in MongoDB
3. Java MongoDB APIs , DBCollection.update()