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The Java Foundation Classes are comparable to the Microsoft Foundation Class Library (MFC). JFC is an extension of the original Java Abstract Windowing Toolkit (AWT). Using JFC and Swing, an additional set of program components, a programmer can write programs that are independent of the windowing system within a particular operating system.
Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible. It is a general-purpose programming language intended to let programmers write once, run anywhere (), [16] meaning that compiled Java code can run on all platforms that support Java without the need to recompile. [17]
If a class does not specify its superclass, it implicitly inherits from java.lang.Object class. Thus all classes in Java are subclasses of Object class. If the superclass does not have a constructor without parameters the subclass must specify in its constructors what constructor of the superclass to use. For example:
A class declared as sealed via the keyword sealed in C# or final in Java or PHP. [38] [39] [40] For example, Java's String class is marked as final. [41] Sealed classes may allow a compiler to perform optimizations that are not available for classes that can be subclassed. [42]
In class-based programming, inheritance is done by defining new classes as extensions of existing classes: the existing class is the parent class and the new class is the child class. If a child class has only one parent class, this is known as single inheritance , while if a child class can have more than one parent class, this is known as ...
Classes may inherit from other classes, so they are arranged in a hierarchy that represents "is-a-type-of" relationships. For example, class Employee might inherit from class Person. All the data and methods available to the parent class also appear in the child class with the same names.
The class keyword can also be used in the form Class.class to get a Class object without needing an instance of that class. For example, String.class can be used instead of doing new String().getClass(). continue Used to resume program execution at the end of the current loop body.
Primitive wrapper classes are not the same thing as primitive types. Whereas variables, for example, can be declared in Java as data types double, short, int, etc., the primitive wrapper classes create instantiated objects and methods that inherit but hide the primitive data types, not like variables that are assigned the data type values.