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Articles on Trending Technologies
Technical articles with clear explanations and examples
What uses are there for "placement new" in C++?
In this section we will see what is the placement new operator in C++. This placement new is another variation of new operator. The normal new operator performs two things. It allocates memory, and then constructs an object in allocated memory.The new operator allocates memory in the heap section and constructs objects there. But for the placement new operator, it constructs object at the given address. To deallocate memory, we can use delete keyword if the memory is allocated using new operator. But for placement new there is no placement delete feature.So in a nutshell, placement new allows you to ...
Read MoreThe size() method of Java AbstractCollection class
The size() method of the AbstractCollection class returns the numbers of elements in the collection. The method returns Integer.MAX_VALUE if the total number of elemnts in the collection exceeds the Interger.MAX_VALUE.The syntax is as follows:public abstract int size()To work with AbstractCollection class in Java, import the following package:import java.util.AbstractCollection;The following is an example to implement AbstractCollection size() method in Java:Exampleimport java.util.ArrayList; import java.util.AbstractCollection; public class Demo { public static void main(String[] args) { AbstractCollection absCollection = new ArrayList(); absCollection.add("Laptop"); absCollection.add("Tablet"); absCollection.add("Mobile"); absCollection.add("E-Book Reader"); ...
Read MoreWhy variables are declared final in Java
A variable cannot be modified after it is declared as final. In other words, a final variable is constant. So, a final variable must be initialized and an error occurs if there is any attempt to change the value.A program that demonstrates a final variable in Java is given as follows −Examplepublic class Demo { public static void main(String[] args) { final double PI = 3.141592653589793; System.out.println("The value of pi is: " + PI); } }OutputThe value of pi is: 3.141592653589793Now let us understand the above program.In the main() method in class ...
Read MoreDoubleStream.Builder accept() method in Java
The accept() method of the DoubleStream class in Java adds an element to the stream being built.The syntax is as follows −void accept(double ele)Here, ele is the element to be inserted into the stream.To use the DoubleStream.Builder class in Java, import the following package −import java.util.stream.DoubleStream;The following is an example to implement DoubleStream.Builder() accept() method in Java −Exampleimport java.util.stream.DoubleStream; public class Demo { public static void main(String[] args) { DoubleStream.Builder builder = DoubleStream.builder(); builder.accept(12.9); builder.accept(25.6); builder.accept(35.8); builder.accept(43.9); builder.accept(56.3); ...
Read MoreThe addAll() method of Java AbstractSequentialList class
The addAll() method of the AbstractSequentialList class inserts all the elements in the specified collection into this list at the specified position. Set the specified position as the parameter.The syntax is as follows:boolean addAll(int index, Collection
Read MoreHow to track the order of insertion using Java collections?
To track the order of insertion, you can use Map.Entry() in case of a Map. Let’s say we have the following LinkedHashMap −Mapmap = new LinkedHashMap(); map.put("Jack", 0); map.put("Tim", 1); map.put("David", 2); map.put("Tom", 3); map.put("Kevin", 4); map.put("Jeff", 5);Now, loop through Map.Entry and get the order of insertion correctly with Key and Value −for (Map.Entryentry: map.entrySet()) { System.out.println(entry.getKey() + " => " + entry.getValue()); }Exampleimport java.util.LinkedHashMap; import java.util.Map; public class Demo { public static void main(String[] args) { Mapmap = new LinkedHashMap(); map.put("Jack", 0); map.put("Tim", 1); map.put("David", ...
Read MoreClass declaration with a method that has a parameter in Java
A class declaration can contain a method that has a parameter in Java. A program that demonstrates this is given as follows:Exampleclass Message { public void messagePrint(String msg) { System.out.println("The message is: " + msg); } } public class Demo { public static void main(String args[]) { Message m = new Message(); m.messagePrint("Java is fun"); } }OutputThe message is: Java is funNow let us understand the above program.The Message class is created with a single member function ...
Read MoreHow to use null value as key in Java HashMap
Yes, you can set null as key in Java HashMap. For this, let’s first create a HashMap with key and value pair −Mapmap = new HashMap(); map.put("Football", "A"); map.put("Squash", "B"); map.put("Cricket", "C"); map.put("Hockey", "D"); map.put("Rugby", "E");Now, let’s add null value as key −map.put(null, "H");You can try to get the value for key as “null” −map.get(null);Exampleimport java.util.HashMap; import java.util.Map; public class Demo { public static final void main(String[] args) { Mapmap = new HashMap(); map.put("Football", "A"); map.put("Squash", "B"); map.put("Cricket", "C"); map.put("Hockey", "D"); ...
Read MoreThe iterator() method of CopyOnWriteArrayList in Java
The iterator() method is used to return an iterator over the elements in this list.The syntax is as followsIterator iterator()To work with CopyOnWriteArrayList class, you need to import the following packageimport java.util.concurrent.CopyOnWriteArrayList;The following is an example to implement CopyOnWriteArrayList class iterator() method in JavaExampleimport java.util.Arrays; import java.util.Iterator; import java.util.concurrent.CopyOnWriteArrayList; public class Demo { public static void main(String[] args) { CopyOnWriteArrayList arrList = new CopyOnWriteArrayList(); arrList.add(50); arrList.add(90); arrList.add(150); arrList.add(200); arrList.add(350); arrList.add(500); arrList.add(650); ...
Read MoreDuplicating Objects using a Constructor in Java
A copy constructor can be used to duplicate an object in Java. The copy constructor takes a single parameter i.e. the object of the same class that is to be copied. However, the copy constructor can only be explicitly created by the programmer as there is no default copy constructor provided by Java.A program that demonstrates this is given as follows −Exampleclass NumberValue { private int num; public NumberValue(int n) { num = n; } public NumberValue(NumberValue obj) { num = obj.num; } public void display() { ...
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