Can we use public and abstract together?

Only public & abstract are permitted in combination to method. Example: public abstract void sum(); We use abstract keyword on method because Abstract methods do not specify a body.

Can public and abstract be used together?

The keywords public and abstract cannot be used together.

Can abstract class have public?

Abstract classes shouldn't have public constructors because they don't make sense. Abstract classes are incomplete, so allowing a public constructor (which anyone could call) wouldn't work as you can't instantiate an instance anyway.

Can abstract class be public or private?

If a method of a class is private, you cannot access it outside the current class, not even from the child classes of it. But, incase of an abstract method, you cannot use it from the same class, you need to override it from subclass and use. Therefore, the abstract method cannot be private.

Can we use abstract and final both with a method?

No, as for an abstract method we have to provide implementation in subclass. To do this abstract method have to be overridden but final methods cannot be overridden.

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Can we override private method?

No, we cannot override private or static methods in Java. Private methods in Java are not visible to any other class which limits their scope to the class in which they are declared.

Can we declare interface as final?

If you make an interface final, you cannot implement its methods which defies the very purpose of the interfaces. Therefore, you cannot make an interface final in Java. Still if you try to do so, a compile time exception is generated saying “illegal combination of modifiers − interface and final”.

Can we declare constructor as private?

Yes, we can declare a constructor as private. If we declare a constructor as private we are not able to create an object of a class. We can use this private constructor in the Singleton Design Pattern.

Can static method be private?

Static methods can be public or private. The static keyword is placed right after the public/private modifier and right before the type of variables and methods in their declarations.

Can abstract method be static?

If you declare a method in a class abstract to use it, you must override this method in the subclass. But, overriding is not possible with static methods. Therefore, an abstract method cannot be static.

Can an abstract class have public abstract methods?

A Java class that is declared using the keyword abstract is called an abstract class. New instances cannot be created for an abstract class but it can be extended. An abstract class can have abstract methods and concrete methods or both.

Can abstract class have constructor?

Like any other classes in Java, abstract classes can have constructors even when they are only called from their concrete subclasses.

Can we have protected method in interface?

Protected members of an interface

In general, the protected members can be accessed in the same class or, the class inheriting it. But, we do not inherit an interface we will implement it. Therefore, the members of an interface cannot be protected.

Can we override final method in Java?

You can declare some or all of a class's methods final. You use the final keyword in a method declaration to indicate that the method cannot be overridden by subclasses. The Object class does this—a number of its methods are final .

Can abstract class can be final?

However, an abstract class can have a final method. This final method is treated like a normal method with a body which cannot be overridden.

Is overriding possible in Java?

In Java, method overriding occurs when a subclass (child class) has the same method as the parent class. In other words, method overriding occurs when a subclass provides a particular implementation of a method declared by one of its parent classes.

Can we override static method?

Overloading is the mechanism of binding the method call with the method body dynamically based on the parameters passed to the method call. Static methods are bonded at compile time using static binding. Therefore, we cannot override static methods in Java.

Can we change value of static variable in C?

When static keyword is used, variable or data members or functions can not be modified again. It is allocated for the lifetime of program.

Can static fields be changed?

A static variable is common for all instances of the class. A final variable can not change after it has been set the first time. So a static final variable in Java is common for all instances of the class, and it can not be changed after it has been set the first time.

Can we create immutable class in Java?

Immutable class in java means that once an object is created, we cannot change its content. In Java, all the wrapper classes (like Integer, Boolean, Byte, Short) and String class is immutable. We can create our own immutable class as well.

Can constructors be virtual?

In C++, the constructor cannot be virtual, because when a constructor of a class is executed there is no virtual table in the memory, means no virtual pointer defined yet. So, the constructor should always be non-virtual. But virtual destructor is possible.

Can constructor be static?

No, we cannot define a static constructor in Java, If we are trying to define a constructor with the static keyword a compile-time error will occur. In general, static means class level. A constructor will be used to assign initial values for the instance variables.

Can interface be static?

Static methods in an interface since java8

Since Java8 you can have static methods in an interface (with body). You need to call them using the name of the interface, just like static methods of a class.

Can we override interface?

No. Interface methods can be implemented. To overload/override a method, that method must be defined first. Interface do not contain method definition.

Can a constructor be final?

Java constructor can not be final

One of the important property of java constructor is that it can not be final. As we know, constructors are not inherited in java. Therefore, constructors are not subject to hiding or overriding.