JAR is a file format that helps in aggregating Java class file, along with its associated metadata and resources into a single file.Creation of a JAR file − The jar cf command can be used, where ‘cf’ means creating the file.jar cf jar_file_name files_to_compressOnce a jar file has been created, a default manifest file is also created. Only one manifest file is present in a specific archive, and it will have the extension ‘mf’ and will be in the pathname. Thismanifest file helps give information about the files that have been compressed/present in the package.Viewing a JAR file − The ... Read More

IteratorIt is used in Collection Framework so as to retrieve elements as and when they are required.public interface IteratorIt can be used with the ‘next’ function to move and access the next elements. The ‘remove’ function can be used to remove an element from the data structure.It is quicker in comparison to Collections, since the number of operations associated with Iterator is less.Below is an example of an iterator working with a list −Example Live Demomport java.io.*; import java.util.*; public class Demo{    public static void main(String[] args){       ArrayList my_list = new ArrayList();       my_list.add("Its");   ... Read More

After an object has been used, it is deallocated from the memory using the Garbage Collector class. The objects are destroyed based on the fact that no reference to that object is present. The Garbage Collector class calls the ‘finalize’ function on the object that needs to be destroyed.What is island of isolation?When two objects ‘a’, and ‘b’ reference each other, and they are not referenced by any other object, it is known as island of isolation.It is a group of objects which reference each other but they are not referenced but other objects of other applications at all.Note − ... Read More

Array is considered to be an object in Java. The reason behind this is that an array can be created using the ‘new’ keyword. The ‘new’ keyword/operator is always used to create an object. This is how an array is perceived as an object.The direct parent class or super class of any array is the ‘Object’ class. Every array type in Java belongs to a certain class. This indicates that there are explicit classes for integer array types, float array types, double array types, and so on.Arrays can be dynamically created, and be assigned variables as well.Let us see an ... Read More

IntUnaryOperator Interface, a functional interface of Java that performs an operation on a single integer-valued operand and also returns an integer value as a result. Since it is a functional interface, we can use it as an assignment target for the lambda expressions or method references. Here, the functional interface means an interface that contains only a single abstract method and exhibits single functionality. Some examples of functional interfaces are Predicate, Runnable, and Comparable interfaces. The IntUnaryOperator interface is defined in the 'java.util.function' package. In this article, we are going to explore the IntUnaryOperator Interface and its built-in methods with ... Read More

String interning is a process wherein a single copy of every distinct string value is stored. In addition to this, the strings can’t be changed too. This way, strings can contain the same data as well as share the same memory. This way, the memory required would be greatly reduced.When the ‘intern’ function is called −It checks the equality between two strings- whether the string object is present in the String Constant pool (SCP) or not.If available, the string is returned by fetching it from the pool. Otherwise, a new String object is created and added to the pool. A ... Read More

Set data structure is used to store unique values only, meaning no duplicate values would be stored in a set. When a HashSet is created, it internally implements a HashMap. An element can be inserted into the HashSet using the ‘add’ function. This internally calls the ‘put’ function since a HashMap would have been internally created. Hence, Set takes in unique values with the help of HashMap.HashMap contains unique key and value pairs, wherein the key and value pairs are inserted using the ‘put’ function. Upon calling the ‘put’ function, a previous value associated with the key or null is ... Read More

The function ‘hashCode’ is used to get the hash code of an object in Java. This is an object of super class Object. It returns the object reference’s memory as an integer. It is a native function, which means no direct method in Java can be used to fetch the reference of the object.For better performace of HashMap, use the hashCode() properly. Basically, this function is used to calculate the bucket and index values. It is defined in the following way −public native hashCode()Since we have mentioned ‘bucket’, it is important to understand what it means. It is an element ... Read More

There are many facts associated with null in Java. We will discuss a few of them here with examples −The default value of any reference variable in Java is always null.Example Live Demopublic class Demo{    private static Object my_obj;    public static void main(String args[]){       System.out.println("The default value of object my_obj is : " + my_obj);    } }OutputThe default value of object my_obj is : nullA class named Demo defines a static object and the main function that shows the default value of this pre-defined object.The not equal to (!=) and comparison (==) operators can be ... Read More

Java was built by sheer accident, a team of developers were busy building a set top box, and began cleaning C++. When they were winding up these changes, they ended up discovering Java and its runtime environment.Many of you might be aware of this, but for those who aren’t, Java wasn’t the original name that was decided for this language. It was ‘Oak’. Sun Marketing system changed the name later when they realized that a company named ‘Oak’ existed.It is a widely used language all over the world, and is considered to be a favourite amongst the developer group, and ... Read More