Before answering this question, let us see two important points about volatile variable. Now, let us answer our original question, Can we make an array volatile in Java? Yes, we can make an array volatile in Java but only the reference variable pointing to the array will be volatile not the elements of the array.…

map() and flatmap() methods are found in Optional class and Stream interfaces in Java 8. We’ll discuss the use of both these methods with respect to Optional and Stream. 1. flapMap() and map() methods in Optional 1.1 Syntax of map() <U> Optional<U> map(Function<? super T, ? extends U> mapper) 1.2 Syntax of flatMap() <U> Optional<U>…

A collection is a group of elements. A collection is an in-memory data structure. Collection supports various operations such as sorting, searching, insertion, manipulation and deletion. In Java, collection framework provides many interfaces like Set, List, Queue and implementation classes like ArrayList, HashSet to represent different type of collections. Stream is basically a sequence of…

A Map maps keys to values. Map provides following two methods to return keys and values of a map: public Collection<V> values() This method returns a Collection view of the values contained in this map. public Set keySet() This method returns a Set view of the keys contained in this map Output

DOM XML parser in Java DOM stands for Document Object Model and represents an XML document in tree format, each element representing tree branches. The XML file will be loaded as a whole and all its contents will be built as an in-memory representation of the tree the document represents. Parsing XML file using DOM…

Both HashMap and HashTable map keys to values. HashTable was introduced in JDK 1.0. As of JDK 1.2, this class was retrofitted to implement the Map interface. Following are the differences between HashTable and HashMap: HashMap HashTable HashMap extends java.util.AbstractMap HashTable extends java.util.Dictionary HashMap allows only one null key and any number of null values.…

Constructors cannot be synchronized. Using the synchronized keyword with a constructor is a syntax error – Illegal modifier for the constructor in type your class name; only public, protected & private are permitted’. Synchronizing constructors doesn’t make sense, because only the thread that creates an object should have access to it while it is being…