Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Java Shell (simply JShell) is a REPL interactive tool for learning the Java and prototyping Java code. It evaluates declarations, statements, and expressions as entered and immediately prints out the result and runs from the command-line.Encapsulation is an important concept in Java to make sure that "sensitive" data has been hidden from users. To achieve this, we must declare a class variable as private and provides public access to get and set methods and update the value of a private variable.In the below code snippet, we have implemented the Encapsulation concept for Employee class.jshell> class Employee { ...> private String firstName; ...> ... Read More
To sort values, use sort() in MongoDB. Let us first create a collection with documents −> db.demo365.insertOne({"FirstName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e57d5b6d0ada61456dc936f") } > db.demo365.insertOne({"FirstName":"Adam"}); { "acknowledged" : true, "insertedId" : ObjectId("5e57d5bad0ada61456dc9370") } > db.demo365.insertOne({"FirstName":"John"}); { "acknowledged" : true, "insertedId" : ObjectId("5e57d5bed0ada61456dc9371") } > db.demo365.insertOne({"FirstName":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e57d5c0d0ada61456dc9372") }Display all documents from a collection with the help of find() method −> db.demo365.find();This will produce the following output −{ "_id" : ObjectId("5e57d5b6d0ada61456dc936f"), "FirstName" : "Chris" } { "_id" : ObjectId("5e57d5bad0ada61456dc9370"), "FirstName" : "Adam" } { "_id" : ... Read More
For this, use $addFields. In that, use the $objectToArray to get the data in the form of keys and values. Use $filter with $indexOfBytes to check if there are any keys with. inside it.Let us first create a collection with documents −> db.demo364.insertOne( ... { ... "details" : { ... "details1.otherdetails.Name" : {"FirstName":"Chris" } ... } ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e57d485d0ada61456dc936d") } > db.demo364.insertOne( ... { ... "details" : { ... "details1.otherdetails.Name" ... Read More
The deleteOne() function in MongoDB deletes at most one matching document from a collection. Let us first create a collection with documents −> db.demo363.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e57d2c3d0ada61456dc9369") } > db.demo363.insertOne({"Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e57d2c7d0ada61456dc936a") } > db.demo363.insertOne({"Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e57d2cad0ada61456dc936b") } > db.demo363.insertOne({"Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e57d2d1d0ada61456dc936c") }Display all documents from a collection with the help of find() method −> db.demo363.find();This will produce the following output −{ "_id" : ObjectId("5e57d2c3d0ada61456dc9369"), "Name" : "Chris" } { "_id" : ObjectId("5e57d2c7d0ada61456dc936a"), ... Read More
Let us create a collection with documents −> db.demo362.insertOne({"ClientName":"John", "ClientProject":"School Management System"}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a77454a481fef8ec7a1c") } > db.demo362.insertOne({"ClientName":"David", "ClientProject":"Library Management System"}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a78454a481fef8ec7a1d") } > db.demo362.insertOne({"ClientName":"Mike", "ClientProject":"Event Tracker"}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a7a054a481fef8ec7a1e") } > db.demo362.insertOne({"ClientName":"Carol", "ClientProject":"Hospital Management System"}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a7b754a481fef8ec7a1f") }Display all documents from a collection with the help of find() method −> db.demo362.find();This will produce the following output −{ "_id" : ObjectId("5e56a77454a481fef8ec7a1c"), "ClientName" : "John", "ClientProject" : "School Management System" } { "_id" : ... Read More
For finding values, use find() in MongoDB. Under that, use dot notation. Let us create a collection with documents −> db.demo361.insertOne({"details":{"FirstName":"Chris", "LastName":"Brown"}}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a61f54a481fef8ec7a19") } > db.demo361.insertOne({"details":{"FirstName":"David", "LastName":"Miller"}}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a62854a481fef8ec7a1a") } > db.demo361.insertOne({"details":{"FirstName":"John", "LastName":"Doe"}}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a63654a481fef8ec7a1b") }Display all documents from a collection with the help of find() method −> db.demo361.find();This will produce the following output −{ "_id" : ObjectId("5e56a61f54a481fef8ec7a19"), "details" : { "FirstName" : "Chris", "LastName" : "Brown" } } { "_id" : ObjectId("5e56a62854a481fef8ec7a1a"), "details" : { "FirstName" : ... Read More
To get the current and previous documents, use sort(). Since we need only 2 documents, therefore, use LIMIT(2).Let us create a collection with documents −> db.demo360.insertOne({id:101, "Name":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a10c54a481fef8ec7a15") } > db.demo360.insertOne({id:102, "Name":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a11254a481fef8ec7a16") } > db.demo360.insertOne({id:103, "Name":"Bob"}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a11a54a481fef8ec7a17") } > db.demo360.insertOne({id:104, "Name":"Mike"}); { "acknowledged" : true, "insertedId" : ObjectId("5e56a11f54a481fef8ec7a18") }Display all documents from a collection with the help of find() method −> db.demo360.find();This will produce the following output −{ "_id" : ObjectId("5e56a10c54a481fef8ec7a15"), "id" : ... Read More
To concatenate in MongoDB, use $concat in $project. Let us create a collection with documents −> db.demo359.insertOne( ... { ... ... Name1: "Chris", ... Name2: "David", ... Subjects: ["MySQL", "MongoDB", "Java"] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e5694cdf8647eb59e5620d0") }Display all documents from a collection with the help of find() method −> db.demo359.find().pretty();This will produce the following output −{ "_id" : ObjectId("5e5694cdf8647eb59e5620d0"), "Name1" : "Chris", "Name2" : "David", "Subjects" : [ "MySQL", "MongoDB", ... Read More
Yes, it works in MongoDB. Let us create a collection with documents −> db.demo358.insertOne({"ClientId":101, "ClientName":"Chris", "ClientAge":34}); { "acknowledged" : true, "insertedId" : ObjectId("5e5692c0f8647eb59e5620cb") } > db.demo358.insertOne({"ClientId":102, "ClientName":"David", "ClientAge":32}); { "acknowledged" : true, "insertedId" : ObjectId("5e5692caf8647eb59e5620cc") } > db.demo358.insertOne({"ClientId":103, "ClientName":"David", "ClientAge":35}); { "acknowledged" : true, "insertedId" : ObjectId("5e5692d2f8647eb59e5620cd") } > db.demo358.insertOne({"ClientId":104, "ClientName":"Bob", "ClientAge":31}); { "acknowledged" : true, "insertedId" : ObjectId("5e5692ddf8647eb59e5620ce") } > db.demo358.insertOne({"ClientId":105, "ClientName":"Chris", "ClientAge":36}); { "acknowledged" : true, "insertedId" : ObjectId("5e5692e7f8647eb59e5620cf") }Display all documents from a collection with the help of find() method −> db.demo358.find();This will produce the following output ... Read More
The NumberInt() is used to explicitly specify 32-bit integers. Let us create a collection with documents −> db.demo357.insertOne( ... { ... "FirstName" : "Chris", ... "Age" : 21, ... "details" : { ... "studentDetails" : { ... "id" : NumberInt(101) ... } ... } ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5e568fa6f8647eb59e5620c9") } > db.demo357.insertOne( ... { ... "FirstName" : "David", ... ... Read More