Programming Articles - Page 2088 of 3366

In this tutorial, we will be discussing a program to understand how to create an unordered map of user defined class in C++.To create an unordered map from a user defined class, we will pass the hash function as the class method being the third argument.Example Live Demo#include using namespace std; //objects of class to be used as key values struct Person {    string first, last;    Person(string f, string l){       first = f;       last = l;    }    bool operator==(const Person& p) const{       return first == p.first && ... Read More

In this article, we will learn about the purpose of using the Optional.ifPresentOrElse() method in Java 9.  The Optional Class The Optional class was introduced in Java 8. Many Java developers face null pointer exceptions to avoid this, we need to put null checks we need to put if, to check if a method is null we can put it in the if statement; otherwise, we have to put it in the else statement. And to check this, we need to put this at multiple points to avoid this situation, We use the Optional class. It avoids the null pointer ... Read More

In this tutorial, we will be discussing a program to understand how to create an unordered map of pairs in C++.Unordered maps are the ones that don't contain hash function for the pairs by default. If we want a hash value for a particular pair, it needs to be passed on explicitly.Example Live Demo#include using namespace std; //to hash any given pair struct hash_pair {    template    size_t operator()(const pair& p) const{       auto hash1 = hash{}(p.first);       auto hash2 = hash{}(p.second);       return hash1 ^ hash2;    } }; int main(){ ... Read More

In this tutorial, we will be discussing a program to understand how to create a List with constructor in C++ STL.List are data structures to store elements in memory in a non-contiguous fashion. They are insertion and deletion quick as compared to vectors.Example Live Demo#include #include using namespace std; //printing the list void print_list(list mylist){    list::iterator it;    //printing all the elements    for (it = mylist.begin(); it != mylist.end(); ++it)       cout

In this tutorial, we will be discussing a program to understand how to add “graphics.h” C/C++ library to gcc compiler in Linux.To do this we are required to compile and install the libgraph package.This includes install build-essential and some external packages>>sudo apt-get install build-essential >>sudo apt-get install libsdl-image1.2 libsdl-image1.2-dev guile-2.0 guile-2.0-dev libsdl1.2debian libart-2.0-dev libaudiofile-dev libesd0-dev libdirectfb-dev libdirectfb-extra libfreetype6-dev libxext-dev x11proto-xext-dev libfreetype6 libaa1 libaa1-dev libslang2-dev libasound2 libasound2-devThen setting the path in the extracted files>>sudo make install >>sudo cp /usr/local/lib/libgraph.* /usr/libExample#include #include #include int main(){    int gd = DETECT, gm;    initgraph(&gd, &gm, NULL);    circle(40, 40, 30);    delay(40000); ... Read More

In this tutorial, we will be discussing a program to understand how vectors work in C/C++.A vector data structure is an enhancement over the standard arrays. Unlike arrays, which have their size fixed when they are defined; vectors can be resized easily according to the requirement of the user.This provides flexibility and reduces the time requirement with arrays to copy the previous elements to the newly created array.Example Live Demo#include #include using namespace std; int main(){    vector myvector{ 1, 2, 3, 5 };    myvector.push_back(8);    //not vector becomes 1, 2, 3, 5, 8    for (auto x : myvector)    cout

In this article, we will learn to import external libraries in JShell in Java 9. JShell is an interactive tool to learn the Java language and prototype Java code. This tool works on the principle of REPL (Read-Evaluate-Print-Loop). Default Imports in JShell By default, JShell automatically imports a few useful Java packages when the JShell session is started. We can type the command /imports to get a list of all these imports. jshell> /imports | import java.io.* | import java.math.* | import java.net.* | import java.nio.file.* | import java.util.* | import java.util.concurrent.* | import java.util.function.* | import java.util.prefs.* | import ... Read More

Since Java 9, we are able to add private methods and private static methods in an interface. The advantage of using private methods in an interface is to reduce code duplication among default and static methods. For instance, if two or more default methods need to share some code, a private method can be created for the same and called from each of the default methods. Different Types of Variables and Methods in an Interface In Java 9, the following variables/methods have been defined in an interface. Constant Variables Abstract Method ... Read More

In this article, we will learn about the use of the Optional.stream() method in Java 9. First, we will learn about the optional class and its method. Then we will see the use cases along with an example.Optional class The Optional class was introduced in Java 8 to reduce the null pointer exception that occurs in Java. It is basically a container for the actual object that needs to be returned by a method. The point here is that if a method returns a null value, which can be null, then that method could return a value instead contained inside ... Read More

In this article, we will learn about the use of the Cleaner class in Java 9. Below, we will first tell the basic usage and then we will know how we can use the Cleaner method practically. Garbage Collector An Object that has been created during the program execution is automatically removed by the Garbage Collector (GC). When an object not referenced by any thread and when JVM determines that this object can't be accessed, then it can be eligible for garbage collection. The finalize() method The Object class has a finalize() method, which is automatically called by GC before it attempts to remove the ... Read More