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Constructors cannot be directly invoked (the keyword “new” invokes them). Constructors should not have non-access modifiers. Java constructors perform the following tasks in the following order: Call the default constructor of the superclass if no constructor is defined. Initialize member variables to the specified values.
In object-oriented programming, an interface or protocol type [a] is a data type that acts as an abstraction of a class. It describes a set of method signatures , the implementations of which may be provided by multiple classes that are otherwise not necessarily related to each other. [ 1 ]
The main differences between constructors and ordinary methods are that constructors are called only when an instance of the class is created and never return anything. Constructors are declared as common methods, but they are named after the class and no return type is specified:
A constructor is a method that is called at the beginning of an object's lifetime to create and initialize the object, a process called construction (or instantiation). Initialization may include an acquisition of resources. Constructors may have parameters but usually do not return values in most languages. See the following example in Java:
Java explicitly distinguishes between interfaces and classes. In C++, multiple inheritance and pure virtual functions make it possible to define classes that function almost like Java interfaces do, with a few small differences. Java has both language and standard library support for multi-threading.
An interface in the Java programming language is an abstract type that is used to declare a behavior that classes must implement. They are similar to protocols.Interfaces are declared using the interface keyword, and may only contain method signature and constant declarations (variable declarations that are declared to be both static and final).
Rather than by calling a constructor, this is accomplished by invoking a factory method to create an object. Factory methods can be specified in an interface and implemented by subclasses or implemented in a base class and optionally overridden by subclasses.
There is a distinction between the definition of an interface and the implementation of that interface; however, this line is blurred in many programming languages because class declarations both define and implement an interface. Some languages, however, provide features that separate interface and implementation.