Programming Articles - Page 2719 of 3363

The functors are the function objects in C++. The functor allows an instance object of some class to be called as if it were an ordinary function. Let us consider a function that takes one argument. We can use this function as function object to do some task on a set of data. The Functors are widely used in STL algorithms like transform(), sort(), etc. Functor vs Regular Function: Need of Functor? Imagine we have a function that takes only one argument, like this: int increment(int x) { return x + 1; } Now, what ... Read More

The void functions are called void because they do not return anything. "A void function cannot return anything" this statement is not always true. From a void function, we cannot return any values, but we can return something other than values. Some of them are like below. A void function can return A void function cannot return any values. But we can use the return statement. It indicates that the function is terminated.ExampleThe following example demonstrates a void function with the return statement: #include using namespace std; void my_func() { cout

In C++, a pointer stores the address of another variable, which means that the pointer itself does not contain a value of its own. However, you can assign a null value or a 0 to a pointer, in which case the pointer will not point to the address of any other variable. NULL: It is special constant that indicates the pointer does not point to any valid memory location i.e., an Empty Pointer. 0: It is an older way to represent a null pointer to indicate that the pointer points to nothing. nullptr: It is introduced in C++11, it ... Read More

The size of a pointer in C/C++ is not fixed. It depends upon different issues like Operating system, CPU architecture etc. Usually it depends upon the word size of underlying processor, for example for a 32 bit computer the pointer size can be 4 bytes and for a 64 bit computer the pointer size can be 8 bytes. So for a specific architecture pointer size will be fixed. It is common to all data types like int *, float * etc. Depending on the system architecture, pointer size may vary. The following table shows the pointer size based on the ... Read More

Stored procedures are sub routines, segment of SQL statements which are stored in SQL catalog. All the applications that can access Relational databases (Java, Python, PHP etc.), can access stored procedures.Stored procedures contain IN and OUT parameters or both. They may return result sets in case you use SELECT statements. Stored procedures can return multiple result sets.Retrieving Results from a procedure:You can call an existing stored procedure using the CallableStatement. The prepareCall() method of the Connection interface accepts the procedure call in string format and returns a callable statement object.CallableStatement cstmt = con.prepareCall("{call sampleProcedure()}");Execute the above created callable statement using ... Read More

MongoDB is a cross-platform, document oriented database that provides, high performance, high availability, and easy scalability. MongoDB works on concept of collection and document.Before you start connecting MongoDB in you need to make sure that you have MongoDB JDBC driver. If not, download the jar from the path Download mongo.jar and, add it to your classpath.ExampleFollowing JDBC program establishes connection with the MongoDB database and creates a collection in it.import com.mongodb.client.MongoDatabase; import com.mongodb.MongoClient; import com.mongodb.MongoCredential; public class CreatingCollection {    public static void main( String args[] ) {       // Creating a Mongo client       MongoClient ... Read More

In C++, a std::vector is a container that is a part of the STL (Standard Template Library). It enables dynamic arrays which can adjust their size automatically. Depending on the requirements and version of C++ being used, there are many ways to initialize a std::vector with hardcoded elements. Initializing a std::vector with Hardcoded Elements Some of the approaches to initialize a std::vector with hardcoded elements in C++: Using Initializer List Using assign() Function Using accumulate() function Initializing Vector Using Initializer List An initializer list is a ... Read More

PostgreSQL is an open source relational database management system (DBMS) developed by a worldwide team of volunteers. PostgreSQL is not controlled by any corporation or other private entity and the source code is available free of charge.PostgreSQL runs on all major operating systems, including Linux, UNIX (AIX, BSD, HP-UX, SGI IRIX, Mac OS X, Solaris, Tru64), and Windows. It supports text, images, sounds, and video, and includes programming interfaces for C / C++, Java, Perl, Python, Ruby, Tcl and Open Database Connectivity (ODBC).Download the latest version of postgresql- from postgresql-jdbc repository.Add downloaded jar file postgresql-(VERSION).jdbc.jar in your class path.ExampleFollowing JDBC program ... Read More

HSQLDB is a relational database management system implemented in pure Java. You can easily embed this database to your application using JDBC. Or you can use the operations separately.Installing HSQLDB:Download the latest version of HSQLDB database.Install HSQLDB following the steps given in HSQLDB Tutorial.Make sure that the HSQLDB database is up and running. The URL to connect to this database is jdbc:hsqldb:hsql://host_name/database_name and the driver class name is org.hsqldb.jdbc.JDBCDriver. Download the driver and set classpath to it.ExampleFollowing JDBC program establishes a connection with HSQL database.import java.sql.Connection; import java.sql.DriverManager; public class ConnectDatabase {    public static void main(String[] args) {   ... Read More

The refreshRow() method of the ResultSet interface refreshes the current row with the most recent value in the database.rs.refreshRow()Assume we have a table named cricketers_data with 7 records as shown below:+----+------------+------------+---------------+----------------+-------------+ | ID | First_Name | Last_Name  | Year_Of_Birth | Place_Of_Birth | Country     | +----+------------+------------+---------------+----------------+-------------+ | 1  | Shikhar    | Dhawan     | 1981-12-05    | Delhi          | India       | | 2  | Jonathan   | Trott      | 1981-04-22    | CapeTown       | SouthAfrica | | 3  | Lumara     | Sangakkara | ... Read More