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The value of a particular duration in the number of nanoseconds can be obtained using the toNanos() method in the Duration class in Java. This method requires no parameters and it returns the duration in the number of nanoseconds.A program that demonstrates this is given as follows −Example Live Demoimport java.time.Duration; public class Demo { public static void main(String[] args) { Duration d = Duration.ofSeconds(1); System.out.println("The duration is: " + d); System.out.println("The number of nanoseconds in the duration is: " + d.toNanos()); } }OutputThe duration is: PT1S The number of ... Read More
PyMongo is a Python distribution containing tools for working with MongoDB. To perform regex queries with PyMongo, the syntax is as follows −db.yourCollectionName.find({'yourCollectionName':{'$regex':'^yourWords'}}).pretty();The above syntax will give all those documents that start from a specific word.To understand the syntax, let us create a collection with the document. The query to create a collection with a document is as follows −> db.performRegex.insertOne({"ClientName":"Larry", "ClientFolderInformation":[ "Folder 1", "Folder 2", "Folder 3", "Folder 4", "Folder 5"], "MainFolderLocation":"/MainFolder/Details/ClientFolder" }); { "acknowledged" : true, "insertedId" : ObjectId("5c8a8b186cea1f28b7aa07f2") } > db.performRegex.insertOne({"ClientName":"Larry", "ClientFolderInformation":[ "ClientFolder 1", "ClientFolder 2", "ClientFolder 3", "ClientFolder 4", "ClientFolder 5"], ... Read More
You can use $unset as well as $pull operator with an update to delete the nth element of an array.Let us create a collection with a document. The query to create a collection with a document is as follows −> db.getNThElementDemo.insertOne({"UserName":"John", "UserAge":23, "ListOfFriends":["Carol", "Sam", "Mike", "Bob"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c94ee7516f542d757e2b43e") } > db.getNThElementDemo.insertOne({"UserName":"David", "UserAge":21, "ListOfFriends":["Chris", "Robert"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c94eeaa16f542d757e2b43f") }Display all documents from a collection with the help of find() method. The query is as follows −> db.getNThElementDemo.find().pretty();The following is the output −{ "_id" : ObjectId("5c94ee7516f542d757e2b43e"), "UserName" ... Read More
A hash table is a data structure which is used to store key-value pairs. Hash function is used by hash table to compute an index into an array in which an element will be inserted or searched.This is a C++ program to Implement Hash Tables.AlgorithmBegin Initialize the table size T_S to some integer value. Create a structure hashTableEntry to declare key k and value v. Create a class hashMapTable: Create a constructor hashMapTable to create the table. Create a hashFunc() function which return key mod T_S. Create a function Insert() to insert element at ... Read More
It is possible to pass some values from the command line to your C++ programs when they are executed. These values are called command line arguments and many times they are important for your program especially when you want to control your program from outside instead of hard-coding those values inside the code.The command line arguments are handled using main() function arguments where argc refers to the number of arguments passed, and argv[] is a pointer array which points to each argument passed to the program. Following is a simple example which checks if there is any argument supplied from ... Read More
To compare two strings, which are numbers, let us first create a table. Following is the query −mysql> create table compareTwoStringsDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Value varchar(100) -> ); Query OK, 0 rows affected (0.52 sec)Following is the query to insert some records in the table using insert command −mysql> insert into compareTwoStringsDemo(Value) values('1235667'); Query OK, 1 row affected (0.66 sec) mysql> insert into compareTwoStringsDemo(Value) values('999999'); Query OK, 1 row affected (0.11 sec) mysql> insert into compareTwoStringsDemo(Value) values('999888'); Query OK, 1 row affected (0.17 sec) mysql> ... Read More
Let us first create a table with Id as auto_increment −mysql> create table DemoTable ( UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserName varchar(20) ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(UserName) values('John'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable(UserName) values('Larry'); Query OK, 1 row affected (0.35 sec) mysql> insert into DemoTable(UserName) values('Chris'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable(UserName) values('Bob'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(UserName) values('Carol'); Query OK, 1 row affected ... Read More
An enumeration of the values in the hash table can be obtained using the method elements() in the class java.security.Provider. This method requires no parameters and it returns the enumeration of the values in the hash table.A program that demonstrates this is given as follows −Example Live Demoimport java.security.*; import java.util.*; public class Demo { public static void main(String[] argv) { try { SecureRandom sRandom = SecureRandom.getInstance("SHA1PRNG"); Provider p = sRandom.getProvider(); Enumeration enumeration; enumeration = p.elements(); System.out.println("The ... Read More
In Linux platform there are many great profiling tools for profiling C++ programs. Valgrind is one of them. It is widely used. It is a programming tool for memory debugging, memory leak detection, and profiling. We can use Valgrind by passing the binary to it and setting the tool to callgrind. First generate the binary by compiling the program$ g++ -o abc.cpp abcNow use valgrind to profile it$ valgrind --tool=callgrind ./abcThis will generate a file called callgrind.out.x. You can read this file using a tool called kcachegrind.If you're using gcc, you can use the inbuilt profiling tool, gprof. You can ... Read More
MySQL uses foreign key constraint instead of inheritance. MySQL does not support table inheritance.You can achieve the same with the help of foreign key constraint. Let us create a table and use the foreign key constraint. The query to create the first table is as follows −mysql> create table Parent_Table -> ( -> ParentId int, -> PRIMARY KEY(ParentId) -> ); Query OK, 0 rows affected (3.59 sec)Now create the second table. The query to create the second table is as follows −mysql> create table Child_Table ... Read More