Why is Java not a pure object oriented language? Can you explain it in detail?
Java is often described as an object-oriented programming (OOP) language, but it is not considered a "pure" object-oriented language. The distinction between pure and impure object-oriented languages typically revolves around how strictly they adhere to the principles of OOP. Here are several reasons why Java is not classified as a pure object-oriented language:
In pure object-oriented languages, everything is treated as an object. This means that even basic data types (like integers, booleans, and characters) should be objects. However, Java has primitive data types (such as int, char, boolean, float, etc.) that are not objects. These primitives are used for performance reasons and are not derived from the Object class. While Java provides wrapper classes (like Integer, Character, Boolean, etc.) that allow these primitives to be treated as objects, the existence of primitive types themselves means that Java does not fully adhere to the pure OOP paradigm.
In pure OOP languages, all methods and variables should belong to objects. However, Java allows the use of static methods and static variables, which belong to the class itself rather than to any specific instance of the class. This means that you can call a static method without creating an instance of the class, which is contrary to the pure OOP principle that emphasizes the use of instances (objects) to access methods and properties.
Java includes features that are not strictly object-oriented. For example, it supports procedural programming constructs, such as static methods and functions that can exist outside of classes. While Java is primarily designed to be an object-oriented language, it still allows for procedural programming paradigms, which is a characteristic of impure OOP languages.
Java supports single inheritance (a class can inherit from only one superclass), which is a design choice that simplifies the language and avoids the complexities associated with multiple inheritance (where a class can inherit from multiple classes). In contrast, some pure object-oriented languages, like Smalltalk, allow for more flexible inheritance models. Java does support multiple inheritance of interfaces, but not of classes, which is a compromise rather than a pure OOP approach.
While interfaces in Java allow for a form of multiple inheritance, they do not provide the same level of functionality as classes. Interfaces can only declare methods (without implementations) and cannot hold state (instance variables). This design choice reflects a compromise in Java's approach to OOP, as it does not fully embrace the concept of objects having both behavior and state in the same way that pure OOP languages do.
In summary, while Java is fundamentally an object-oriented language and encourages the use of objects and classes, it incorporates features and constructs that deviate from the principles of pure object-oriented programming. The presence of primitive data types, static methods, procedural programming features, and limitations on inheritance contribute to its classification as an impure object-oriented language. These design choices were made to enhance performance, usability, and simplicity, which are important considerations in practical software development.