Object Class is the parent class of all classes in java.
Every class in the Java system is a descendant (direct or indirect) of the Object class.
Instance is method defined in a class which is only accessable through the Object of the class are called Instance method.
Private members are not inherited from the parent class.
Object is the topmost class in the Java Class hierarchy. There is no Class above Object. All classes in Java are implicitly derived from Object.
If you mean Java's RuntimeException class, its parent class is java.lang.Exception
Java source files have the .java extension, compiled Java class files have the .class extension.
In Java, or in any object oriented language such as C++, a method defined in super (parent) class does not need to be defined in a subclass, because that is the primary purpose of inheritance. Object oriented programming allows you to define and declare a class that implements the behavior for an object. Inheritance allows you to refine, or subclass, that class by "reusing" all of the functionality of the parent class into the sub class, adding additional definition and declaration for the sub class. If the subclass needs to change a parent class method, it can overload that method. This is called abstraction.
Private members are not inherited from the parent class.
Object is the topmost class in the Java Class hierarchy. There is no Class above Object. All classes in Java are implicitly derived from Object.
Having a parent class in Java is not mandatory. It is a good approach to extend from a parent class that has much of the functionality that the current class needs already coded. This helps us re-use functionality/code and avoid redundant/duplicate code.
If you mean Java's RuntimeException class, its parent class is java.lang.Exception
Java does not support multiple inheritance; a subclass cannot have more than one parent. Java compensates for this with interfaces. A class can implement multiple interfaces, but can only extend one class.
Java source files have the .java extension, compiled Java class files have the .class extension.
It is basically the same as inheritance in other languages. A derived class can inherit from a parent class, meaning that the derived class will have the characteristics (variables, and procedures - called fields, and methods, in this case) of the parent class. It may also have additional characteristics, defined directly in the derived class.
You use function overriding in Java when you inherit a bunch of features from a class and for a few particular cases alone, you do not wish to use the functionality of the parent class and wish to implement a custom feature in your class. In such cases, you create a method in your class with the same name and signature as in your parent class, thereby overloading it. this way only your current class will be used by the JVM unless specifically invoked by using the super keyword.
In Java, or in any object oriented language such as C++, a method defined in super (parent) class does not need to be defined in a subclass, because that is the primary purpose of inheritance. Object oriented programming allows you to define and declare a class that implements the behavior for an object. Inheritance allows you to refine, or subclass, that class by "reusing" all of the functionality of the parent class into the sub class, adding additional definition and declaration for the sub class. If the subclass needs to change a parent class method, it can overload that method. This is called abstraction.
Inheritance in Java refers to the feature wherein the code/functionality of one class can be used in another class that extends this class. Example: public class Parent { ... .. } public class Child extends Parent { ... .. . } Here the class Child extends the class Parent and hence the methods of Parent are available for Child to use. This way we are re-using the code in the parent class in the child class instead of re-writing the whole thing again.
Classes in Java inherit constructors from their parent classes. If you don't explicitly define a parent class, then Object is used, which has only the default empty constructor. That "default" constructor is only there when defined by the parent class, so classes which do not have a no-argument constructor will not allow subclasses to automatically use it. This is implemented this way because of the special nature of constructors. Java could not always provide a default constructor because it could not guarantee that all class members would be properly created or initialized.
Oracle, the parent company of Java, has all of the information needed on this topic. University of Phoenix offers courses on Javascript as does ITT Technical Institute.