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You can use $in operator to check if a value is in an array or not. Let us first create a collection with documents −> db.valueInArrayDemo.insertOne({"UserName":"John", "UserMessage":["Hi", "Hello", "Bye"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd684cf7924bb85b3f48959") } > db.valueInArrayDemo.insertOne({"UserName":"Larry", "UserMessage":["Thank You", "Amazing", "Nice"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd684d27924bb85b3f4895a") } >db.valueInArrayDemo.insertOne({"UserName":"Carol", "UserMessage":["Awesome", "Bye", "Cool"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd684d87924bb85b3f4895b") }Following is the query to display all documents from a collection with the help of find() method −> db.valueInArrayDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cd684cf7924bb85b3f48959"), "UserName" : "John", "UserMessage" : [ "Hi", "Hello", ... Read More
Here we will see the Bind function and the placeholders in C++. Sometimes we need to manipulate the operation of some functions as we need. We can use some default parameters to get some essence of manipulating.In C++11, one new feature is introduced, called the bind function. This helps us to do such manipulating in some easier fashion. To use these features, we have to use header file.Bind functions with the help of placeholders helps to determine the positions, and number of arguments to modify the function according to desired outputs.Placeholders are namespaces which detect the position of a ... Read More
The valueOf() method of the Enum class in java accepts a String value and returns an enum constant of the specified type.ExampleLet us create an enum with name Vehicles with 5 constants representing models of 5 different scoters with their prices as values, as shown below −enum Vehicles { //Constants with values ACTIVA125(80000), ACTIVA5G(70000), ACCESS125(75000), VESPA(90000), TVSJUPITER(75000); //Instance variable private int price; //Constructor to initialize the instance variable Vehicles(int price) { this.price = price; } ... Read More
The HTML DOM input FileUpload type property returns the value of type attribute of an element in an HTML document.SyntaxFollowing is the syntax −object.typeExampleLet us see an example of HTML DOM input file upload type property − Live Demo body{ text-align:center; background-color:#52B2CF; color:#fff; } .btn{ background-color:coral; border:none; height:2rem; border-radius:50px; width:60%; margin:1rem auto; display:block; color:#fff; outline:none; } ... Read More
The ()(parenthesis) brackets play an important role in accessing a function. Accessing a function without () will return the function definition instead of the function result. If the function is accessed with () then the result can be obtained.Without ()ExampleIn the following example, the function is accessed without () so the function definition is returned instead of the result as shown in the output.Live Demo function toCelsius(f) { return (5/9) * (f-32); } document.write(toCelsius); Outputfunction toCelsius(f) { return (5/9) * (f-32); ... Read More
Let’s first create a List string:List list = Arrays.asList("David", "Tom", "Ken", "Yuvraj", "Gayle");Now transform the above list to upper case:list.stream().map(players -> players.toUpperCase())To display, use forEach():list.stream().map(players -> players.toUpperCase()) .forEach(players -> System.out.print(players + ""));The following is an example to transform List string to upper case:Exampleimport java.util.Arrays; import java.util.List; public class Demo { public static void main(final String[] args) { List list = Arrays.asList("David", "Tom", "Ken", "Yuvraj", "Gayle"); System.out.print("List = "+list); System.out.print("Uppercase strings = "); list.stream().map(players -> players.toUpperCase()) .forEach(players -> System.out.print(players + "")); } }OutputList = [David, Tom, Ken, ... Read More
This example demonstrate about Create and Manage Notification Channels in AndroidStep 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.Step 2 − Add the following code to res/layout/activity_main.xml. Step 3 − Add a sound into raw folderStep 4 − Add the following code to src/MainActivity.javapackage app.tutorialspoint.com.notifyme ; import android.app.NotificationChannel ; import android.app.NotificationManager ; import android.content.ContentResolver ; import android.content.Context ; import android.graphics.Color ; import android.media.AudioAttributes ; import android.net.Uri ; import android.support.v4.app.NotificationCompat ; import android.support.v7.app.AppCompatActivity ; import android.os.Bundle ; import android.view.View ; import ... Read More
Let us implement the above syntax in order to find all documents in MongoDB with field name “StudentFirstName”. The query is as follows −> db.getCollectionNames().forEach(function(myCollectionName) { ... var frequency = db[myCollectionName].find({"StudentFirstName": {$exists: true}}).count(); ... if (frequency > 0) { ... print(myCollectionName); ... } ... });This will produce the following output −multiDimensionalArrayProjection removeKeyFieldsDemo stringOrIntegerQueryDemoLet us verify the removeKeyFieldsDemo collection has field with name “StudentFirstName” or not. Following is the query −> db.removeKeyFieldsDemo.find({"StudentFirstName":{$exists:true}});This will produce the following output displaying the StudentFirstName field exist −{ "_id" : ObjectId("5cc6c8289cb58ca2b005e672"), "StudentFirstName" : "John", "StudentLastName" : "Doe" } { "_id" ... Read More
Forgotten timers/callbacksThere are two timing events in javascript namely setTimeout() and setInterval(). The former executes a function after waiting a specified number of milliseconds, whereas the latter executes a function periodically(repeats for every certain interval of time).When any object is tied to a timer callback, it will not be released until the timeout happens. In this scenario timer resets itself and runs forever till the completion of timeout there by disallowing garbage collector to remove the memory.These timers are most frequent cause of memory leaks in javascript.ExampleIn the following example, the timer callback and its tied object(tiedObject) will not be ... Read More
Use aggregate framework along with $ifNull operator for this. The $concatArrays in aggregation is used to concatenate arrays. Let us first create a collection with documents −>db.concatenateArraysDemo.insertOne({"FirstSemesterSubjects": ["MongoDB", "MySQL", "Java"], "SecondSemesterSubjects":["C", "C++", ]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd687707924bb85b3f4895c") } > db.concatenateArraysDemo.insertOne({"FirstSemesterSubjects":["C#", "Ruby", "Python"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd687927924bb85b3f4895d") } >db.concatenateArraysDemo.insertOne({"FirstSemesterSubjects":["HTML", "CSS", "Javascript"], "SecondSemesterSubjects":["CSS", "Javascript"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd687bb7924bb85b3f4895e") }Following is the query to display all documents from a collection with the help of find() method −> db.concatenateArraysDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cd687707924bb85b3f4895c"), ... Read More