What are interfaces and packages in Java?
Key Differences Between Packages and Interfaces in Java
A package is a group of classes and interfaces together whereas, an interface is a group of abstract methods. Package is created using a keyword package whereas, an interface is created using a keyword interface.
What are the classes in Java util package?
Package java. util
|HashMap<K,V>||Hash table based implementation of the Map interface.|
|HashSet<E>||This class implements the Set interface, backed by a hash table (actually a HashMap instance).|
|Hashtable<K,V>||This class implements a hash table, which maps keys to values.|
Can package have interfaces?
Introduction to Packages
A package is a mechanism to group the similar type of classes, interfaces and sub-packages and provide access control.
Is overriding possible in Java?
In Java, methods are virtual by default. We can have multilevel method-overriding. Overriding vs Overloading : … Overriding is about same method, same signature but different classes connected through inheritance.
What are the advantages of interface in java?
Why do we use interface ?
- It is used to achieve total abstraction.
- Since java does not support multiple inheritance in case of class, but by using interface it can achieve multiple inheritance .
- It is also used to achieve loose coupling.
- Interfaces are used to implement abstraction.
What are the benefits of packages and interfaces?
Programmers can define their own packages to bundle a group of classes/interfaces, etc. It is a good practice to group related classes implemented by you so that a programmer can easily determine that the classes, interfaces, enumerations, and annotations are related.
Can constructor be private?
Yes. Class can have private constructor. Even abstract class can have private constructor. By making constructor private, we prevent the class from being instantiated as well as subclassing of that class.
What is util * in Java?
Java util ( java. util. * ) package contains collection framework . Java collections framework contains collection classes , classes related to date and time , event model , internationalization , and miscellaneous utility classes . … util ) package , you can do access all these classes and methods .
Is ArrayList an interface in Java util package?
It is found in the java.util package. It is like the Vector in C++. The ArrayList in Java can have the duplicate elements also. It implements the List interface so we can use all the methods of List interface here.
What is a UTIL in Java?
The final Java package, java. util, contains a collection of utility classes. Data Structure Classes. A variety of useful classes implementing standard computer science data structures: including BitSet, Dictionary, Hashtable, Stack and Vector.