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Articles on Trending Technologies
Technical articles with clear explanations and examples
Is main method compulsory in Java?
To compile a program, you doesn’t really need a main method in your program. But, while execution JVM searches for the main method. In the Java the main method is the entry point Whenever you execute a program in Java JVM searches for the main method and starts executing from it.The main method must be public, static, with return type void, and a String array as argument.public static int main(String[] args){ }You can write a program without defining a main it gets compiled without compilation errors. But when you execute it a run time error is generated saying “Main method ...
Read MoreSort a list that places nulls first in Java
Let us create a list first with string elements. Some of the elements are null in the List:List list = Arrays.asList("Jack", null, "Thor", null, "Loki", "Peter", null, "Hulk");Now, sort the above list and place nulls first with nullsFirst:list.sort(Comparator.nullsFirst(String::compareTo));The following is an example to sort a List that places nulls first:Exampleimport java.util.Arrays; import java.util.Comparator; import java.util.List; public class Demo { public static void main(String... args) { List list = Arrays.asList("Jack", null, "Thor", null, "Loki", "Peter", null, "Hulk"); System.out.println("Initial List = "+list); list.sort(Comparator.nullsFirst(String::compareTo)); System.out.println("List placing nulls first = "+list); ...
Read MoreHow do I catch a Ctrl+C event in C++?
The CTRL + C is used to send an interrupt to the current executing task. In this program, we will see how to catch the CTRL + C event using C++.The CTRL + C is one signal in C or C++. So we can catch by signal catching technique. For this signal, the code is SIGINT (Signal for Interrupt). Here the signal is caught by signal() function. Then one callback address is passed to call function after getting the signal.Please see the program to get the better idea.Example#include #include #include #include using namespace std; // Define ...
Read MoreGet the count of the most frequently occurring values in MySQL?
For this, use the aggregate function COUNT() along with GROUP BY. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Value int ); Query OK, 0 rows affected (0.74 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(Value) values(976); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable(Value) values(67); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable(Value) values(67); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable(Value) values(1); Query OK, 1 row affected (0.27 sec) mysql> ...
Read MoreIncrement a field in MongoDB document which is embedded?
Let’s say, here we are incrementing StudentScores for MongoDB which is inside StudentDetails −... "StudentScores": { ... "StudentMathScore": 90, ... "StudentMongoDBScore": 78 ... }Let us first create a collection with documents −> db.embeddedValueIncrementDemo.insertOne( ... { ... "StudentDetails": { ... "StudentScores": { ... "StudentMathScore": 90, ... "StudentMongoDBScore": 78 ... } ... } ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5cd2b670345990cee87fd896") }Following is the query to display ...
Read MoreHow to perform $gt on a hash in a MongoDB document?
The $gt is for greater than, wherein select those documents where the value of the field is greater than the specified value. Let us first create a collection with documents −> db.performQueryDemo.insertOne({"PlayerDetails":{"PlayerScore":1000, "PlayerLevel":2}, "PlayerName":"Chris"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7eba41a844af18acdffa9") } > db.performQueryDemo.insertOne({"PlayerDetails":{"PlayerScore":0, "PlayerLevel":1}, "PlayerName":"Robert"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7ebbb1a844af18acdffaa") } > db.performQueryDemo.insertOne({"PlayerDetails":{"PlayerScore":-10, "PlayerLevel":0}, "PlayerName":"Larry"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7ebd41a844af18acdffab") } > db.performQueryDemo.insertOne({"PlayerDetails":{"PlayerScore":1, "PlayerLevel":1}, "PlayerName":"David"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd7ebe31a844af18acdffac") }Following is the query to display all documents from a collection with the help of ...
Read MoreWhat is instance variable hiding in Java?
Whenever you inherit a superclass a copy of superclass’s members is created at the subclass and you using its object you can access the superclass members.If the superclass and the subclass have instance variable of same name, if you access it using the subclass object, the instance variables of the subclass hides the instance variables of the superclass irrespective of the types. This mechanism is known as field hiding or, instance variable hiding.But, since it makes code complicated field hiding is not recommended.ExampleIn the following example we have two classes Super and Sub one extending the other. They both have ...
Read MoreJava Program to sort Integer list in reversed order
Following is our integer array:Integer[] arr = {20, 50, 100, 150, 200, 250, 300, 350, 400, 500};Now convert the above Integer array to List:List list = new ArrayList(Arrays.asList(arr));Now, to sort the above Integer list in reversed order:Comparator initialComp = Integer::compare; Comparator revComp = initialComp.reversed(); Collections.sort(list, revComp);The following is an example to sort Integer list in reversed order:Exampleimport java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import java.util.Comparator; import java.util.List; public class Demo { public static void main(String[] args) { Integer[] arr = {20, 50, 100, 150, 200, 250, 300, 350, 400, 500}; List list = new ...
Read MoreHow to determine whether C++ code has been compiled in 32 or 64 bit?
In C++, there is no direct way to check the environment architecture. There are two Macros for Windows systems, that can be used to check the architecture. These macros are _WIN64, and _WIN32. When the system is 64-bit, then the _WIN64 will be 1, otherwise the _WIN32 will be 1. So using macro checking, we can identify the architectureExample#include using namespace std; int main() { #ifdef _WIN64 cout
Read MoreHow to get notified when a notification is notified?\\n
This example demonstrate about How to get notified when a notification is notifiedStep 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 the following code to src/MainActivity.package app.tutorialspoint.com.notifyme ; import android.app.NotificationChannel ; import android.app.NotificationManager ; import android.os.Bundle ; import android.support.v4.app.NotificationCompat ; import android.support.v7.app.AppCompatActivity ; import android.view.View ; public class MainActivity extends AppCompatActivity { public static final String NOTIFICATION_CHANNEL_ID = "10001" ; private final static String default_notification_channel_id = ...
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