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Articles by Maruthi Krishna
Page 7 of 50
Can we change the access specifier from (public) while implementing methods from interface in Java?
An interface in Java is a specification of method prototypes. Whenever you need to guide the programmer or, make a contract specifying how the methods and fields of a type should be you can define an interface.To create an object of this type you need to implement this interface, provide a body for all the abstract methods of the interface and obtain the object of the implementing class.All the methods of the interface are public and abstract and, we will define an interface using the interface keyword as shown below −interface MyInterface{ public void display(); public void setName(String ...
Read MoreHow to hide unsupported interface methods from class in Java?
Actually you can’t, once you implement an interface it is a must to provide implementation to all its methods or, make the class abstract. There is no way to skip methods of an interface without implementing (unless they are default methods). Still, if you try to skip implementing methods of an interface a compile-time error would be generated.Exampleinterface MyInterface{ public static int num = 100; public void sample(); public void getDetails(); public void setNumber(int num); public void setString(String data); } public class InterfaceExample implements MyInterface{ public static int num = 10000; public void ...
Read MoreWhat happens if we overload default methods of an interface in java?
An interface in Java is similar to a class but, it contains only abstract methods and fields which are final and static.Since Java8 static methods and default methods are introduced in interfaces.Default methods − Unlike other abstract methods these are the methods that can have a default implementation. If you have a default method in an interface, it is not mandatory to override (provide body) it in the classes that are already implementing this interface.In short, you can access the default methods of an interface using the objects of the implementing classes.Exampleinterface MyInterface{ public static int num = 100; ...
Read MoreCan we overload methods of an interface in Java?
Polymorphism is the ability of an object to perform different actions (or, exhibit different behaviors) based on the context.Overloading is one of the mechanisms to achieve polymorphism where a class contains two methods with the same name and different parameters.Whenever you call this method the method body will be bound with the method call based on the parameters.ExampleIn the following Java program, the Calculator class has two methods with name addition the only difference is that one contains 3 parameters and the other contains 2 parameters.Here, we can call the addition method by passing two integers or three integers. Based ...
Read MoreHow to override only few methods of interface in Java?
Once you implement an interface from a concrete class you need to provide implementation to all its methods. If you try to skip implementing methods of an interface at compile time an error would be generated.Exampleinterface MyInterface{ public void sample(); public void display(); } public class InterfaceExample implements MyInterface{ public void sample(){ System.out.println("Implementation of the sample method"); } public static void main(String args[]) { InterfaceExample obj = new InterfaceExample(); obj.sample(); } }Compile-time errorInterfaceExample.java:5: error: InterfaceExample is not abstract and does not override abstract method display() ...
Read MoreIs parent child hierarchy important on throws while overriding in Java?
When you try to handle an exception (checked) thrown by a particular method, you need to catch it using the Exception class or super class of the Exception occurred.In the same way while overriding the method of a super class, if it throws an exception −The method in the sub-class should throw the same exception or its sub type.The method in the sub-class should not throw its super type.You can override it without throwing any exception.When you have three classes named Demo, SuperTest and, Super in (hierarchical) inheritance, if Demo and SuperTest have a method named sample().Exampleclass Demo { ...
Read MoreWhen overriding clone method, why do we need to declare it as public in Java?
The clone() method belongs to the class named Object of the java.lang package, it accepts an object as a parameter creates and returns a copy of it.In order to use this method, you need to make sure that your class implements the Cloneable (marker) interface.Examplepublic class CloneExample implements Cloneable { private String name; private int age; public CloneExample(String name, int age){ this.name = name; this.age = age; } public void displayData(){ System.out.println("Name : "+this.name); System.out.println("Age : "+this.age); } public static void ...
Read MoreWhat happens when a subclass object is assigned to a superclass object in Java?
Converting one data type to others in Java is known as casting.If you convert a higher datatype to lower datatype, it is known as narrowing (assigning higher data type value to the lower data type variable).char ch = (char)5;If you convert a lower data type to a higher data type, it is known as widening (assigning lower data type value to the higher data type variable).Int i = 'c';Similarly, you can also cast/convert an object of one class type to others. But these two classes should be in an inheritance relation. Then, If you convert a Super class to subclass ...
Read MoreIs it possible to override a Java method of one class in same?
When we have two classes where one extends another and if, these two classes have the same method including parameters and return type (say, sample) the method in the subclass overrides the method in the superclass.i.e. Since it is an inheritance. If we instantiate the subclass a copy of superclass’s members is created in the subclass object and, thus both methods are available to the object of the subclass.But if you call the method (sample), the sampling method of the subclass will be executed overriding the super class’s method.Exampleclass Super{ public static void sample(){ System.out.println("Method of ...
Read MoreHow to access a derived class member variable by an interface object in Java?
When you try to hold the super class’s reference variable with a sub class object, using this object you can access the members of the super class only, if you try to access the members of the derived class using this reference you will get a compile time error.Exampleinterface Sample { void demoMethod1(); } public class InterfaceExample implements Sample { public void display() { System.out.println("This ia a method of the sub class"); } public void demoMethod1() { System.out.println("This is demo method-1"); } public static void main(String args[]) { ...
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