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Java Articles
Page 68 of 450
Can we create an object for an interface in java?
No, you cannot instantiate an interface. Generally, it contains abstract methods (except default and static methods introduced in Java8), which are incomplete.Still if you try to instantiate an interface, a compile time error will be generated saying “MyInterface is abstract; cannot be instantiated”.In the following example we an interface with name MyInterface and a class with name InterfaceExample.In the interface we have an integer filed (public, static and, final) num and abstract method demo().From the class we are trying to − create an object of the interface and print the num value.Exampleinterface MyInterface{ public static final int num = ...
Read MoreCan abstract method declaration include throws clause in java?
A method which does not have body is known as abstract method. It contains only method signature with a semi colon and, an abstract keyword before it.public abstract myMethod();Yes, you can throw and exception from an abstract class.ExampleIn the following Java program, we have a two classes: one abstract class with name MyClass which have an abstract method (display()) and, another class that extends the abstract class.Here, the display() method abstract class throws an IOException.Exampleimport java.io.IOException; abstract class MyClass { public abstract void display() throws IOException; } public class AbstractClassExample extends MyClass{ public void display() throws IOException { ...
Read MoreCan the abstract methods of an interface throw an exception in java?
Yes, the abstract methods of an interface can throw an exception.ExampleIn the following example the interface (MyInterface) contains an abstract method with name display, which throws an IOException.import java.io.IOException; abstract interface MyInterface { public abstract void display()throws IOException ; }Rules to be followedYou need to follow the rules given below while implementing such method −If the abstract method in the interface throws certain exception. The implemented method can throw the same exception as shown below −Example 1import java.io.IOException; abstract interface MyInterface { public abstract void display()throws IOException ; } public class InterfaceExample implements MyInterface{ public void display()throws ...
Read MoreWhat happens if the subclass does not override abstract methods in java?
A method which does not have body is known as abstract method. It contains only method signature with a semi colon and, an abstract keyword before it.public abstract myMethod();To use an abstract method, you need to inherit it by extending its class and provide implementation to it.A class which contains 0 or more abstract methods is known as abstract class. If it contains at least one abstract method, it must be declared abstract.Extending an abstract classOnce you extend an abstract class in Java you need to override all the abstractmethods in it or, declare it abstract. If you don’t, a ...
Read MoreHow to write a class inside an interface in Java?
Defining a class within an interface is allowed in Java. If the methods of an interface accept a class as an argument and the class is not used elsewhere, in such cases we can define a class inside an interface.ExampleIn the following example we have an interface with name CarRentalServices and this interface has two methods that accepts an object of the class Car as an argument. Within this interface we have the class Car.interface CarRentalServices { void lendCar(Car c); void collectCar(Car c); public class Car{ int carId; String carModel; ...
Read MoreCan we write an interface without any methods in java?
Yes, you can write an interface without any methods. These are known as marking interfaces or, tagging interfaces.A marker interface i.e. it does not contain any methods or fields by implementing these interfaces a class will exhibit a special behavior with respect to the interface implemented.ExampleConsider the following example, here we have class with name Student which implements the marking interface Cloneable. In the main method we are trying to create an object of the Student class and clone it using the clone() method.import java.util.Scanner; public class Student implements Cloneable { int age; String name; public Student ...
Read MoreHow to convert a Date object to LocalDate object in java?
To convert a Date object to LocalDate object in Java −Convert the obtained date object to an Instant object using the toInstant() method.Instant instant = date.toInstant();Create the ZonedDateTime object using the atZone() method of the Instant class.ZonedDateTime zone = instant.atZone(ZoneId.systemDefault());Finally, convert the ZonedDateTime object to the LocalDate object using the toLocalDate() method.LocalDate givenDate = zone.toLocalDate();ExampleFollowing example accepts a name and Date of birth from the user in String formats and converts it to LocalDate object and prints it.import java.text.ParseException; import java.text.SimpleDateFormat; import java.time.Instant; import java.time.LocalDate; import java.time.ZoneId; import java.time.ZonedDateTime; import java.util.Date; import java.util.Scanner; public class DateToLocalDate { public static void main(String ...
Read MoreHow many times finalize method will be invoked? who invokes finalize() method in Java?
The finalize() method belongs to the Object class. Right before closing an object, the garbage collector makes sure that there are no more references to it and, calls the finalize() method on it.Therefore, once you override the finalize() method in it, you can do all the cleanup activity like closing the resources like database connection, network connection, etc.protected void finalize throws Throwable{}It is invoked only once during the execution of a program.Following are some notable points about the finalize method.Since this method belongs the Object class, which is the super class of all the classes in java, you can override ...
Read MoreCan we pass objects as an argument in Java?
Yes, you can pass objects as arguments in Java. Consider the following example: Here we have a class with name EmployeeExampleIn the following Java example, we a have a class with two instance variables name and age and a parameterized constructor initializing these variables.We have a method coypObject() which accepts an object of the current class and initializes the instance variables with the variables of this object and returns it.In the main method we are instantiating the Student class and making a copy by passing it as an argument to the coypObject() method.import java.util.Scanner; public class Student { private ...
Read MoreWhat are the main shift operators provided by Java? Explain with an example?
Java provides three shift operators namely −Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand.Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand.Shift right zero fill operator. The left operands value is moved right by the number of bits specified by the right operand and shifted values are filled up with zeros.Examplepublic class Test { public static void main(String args[]) { int a = 60;/* 60 = 0011 1100 */ ...
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