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This question is still unanswered. Can you please provide an answer. | ||||
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Like Discuss Correct / Improve  Threads  Thread class  runnable interface | ||||
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Ans. Abstract Classes provide default implementations of methods that are inherited by the classes that extend them, which was not the case for Interfaces. This changed in Java 8, where default implementations are provided for methods. | ||||
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Like Discuss Correct / Improve  abstract classes  interfaces  default method Asked in 1 Companies expert | ||||
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Ans. Interfaces don't have member elements and method definitions that could cause diamond problem. With Java 8, Interfaces have default method definitions. This could have created diamond problem but Java introduced a compile time check for "duplicate default methods" in case same method is derived from multiple interfaces and no definition is overridden by the class. | ||||
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Like Discuss Correct / Improve  diamond problem  interfaces  java 8  default methods | ||||
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Ans. No. No interface provides any implementation and hence the declaration isn't viable. | ||||
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Like Discuss Correct / Improve  interface basic | ||||
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Ans. Yes , we can have an interface that is part of a class. | ||||
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Like Discuss Correct / Improve  inner classes   inner interface  nested classes | ||||
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Ans. Such a class still can have member elements which can be inherited and hence facilitate code reuse. Moreover Abstract class can have non final static elements whereas interfaces are only allowed to have static final elements. | ||||
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Like Discuss Correct / Improve  abstract class   interfaces Asked in 2 Companies Basic | ||||
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This question is still unanswered. Can you please provide an answer. | ||||
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Like Discuss Correct / Improve  core interfaces of Spring mvc | ||||
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Ans. Session,SessionFactory,Configuration,Transaction,query and Criteria | ||||
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Like Discuss Correct / Improve  core interfaces of Hibernate Asked in 1 Companies   frequent | ||||
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Ans. Executor - Simple Interface that supports launching new tasks. ExecutorService - Subinterface of Executor, which adds features that help manage the lifecycle, both of the individual tasks and of the Executor itself. ScheduledExecutorService - Subinterface of ExecutorService, supports future and-or periodic execution of tasks. | ||||
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Like Discuss Correct / Improve  Executor Interfaces Asked in 1 Companies | ||||
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This question was recently asked at 'GGK Technologies'.This question is still unanswered. Can you please provide an answer. | ||||
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Like Discuss Correct / Improve  marker interfaces  interfaces Asked in 1 Companies expert   rare | ||||
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Ans. 10 | ||||
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Like Discuss Correct / Improve  interfaces  coding  code intermediate | ||||
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Ans. It will print 4 because member elements of an interface are implicitly static and hence the concept of overriding doesn't work. | ||||
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Like Discuss Correct / Improve  interfaces  coding  code  extending interfaces  diamond interfaces Asked in 1 Companies intermediate | ||||
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Ans. Interface that is declared inside the interface or class, is known as nested interface. It is static by default. | ||||
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Ans. Yes, we can define an inner class within interface.Inside the interface, the inner class is implicitly public static. So the following is legit in Java public interface BuggyBreadInterface { void doSomething(); public class BuggyBreadClass implements BuggyBreadInterface{ void doSomething(){ System.out.println("Do something"); } } } | ||||
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Like Discuss Correct / Improve  inner classes  inner class in interface  nested classes | ||||
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Ans. java.util.Collection | ||||
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Like Discuss Correct / Improve  collection interface  collections | ||||
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Ans. Here is the list of classes that implements Collections Interface - http://www.buggybread.com/2015/02/java-collections-classes-that-implement.html Having Collection interface to extend Cloneable interface would mean necessarily implement clone method by all implementing classes. As not all collection classes allow duplicate elements, it makes no sense to clone elements for them. | ||||
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Like Discuss Correct / Improve  cloneable  collections  collection interface  cloning | ||||
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Ans. Implementing Comparable interface means that the elements of the class are comparable i.e the class provides the implementation of compareTo method that would help comparing the elements. This is usually required if we are planning to sort elements of a collection, If compareTo method is not defined , the sorting class / method could never understand a way to compare its elements in order to sort them. | ||||
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Ans. Yes, a Class is supposed to define all abstract methods declared in the interface. With Java 8 , Interfaces can have default methods which need not be implemented by the implementing class. | ||||
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Like Discuss Correct / Improve  interfaces | ||||
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Ans. Default methods results in multiple inheritance of behavior and not of state. In case we try to implement multiple interfaces with default method having same name and signature, and don't override it in implementation class, it will throw an error. For example - interface MyInterface { public void default myMethod(){ } } interface MyInterface2 { public void default myMethod(){ } } class MyClass implements MyInterface,MyInterface2 { } This code will compilation error "Duplicate Default Method" if we specify the definition of myMethod() in myClass, compiler won't complain and there is no conflict and MyClass can use overridden definition. But if we don't override myMethod() in MyClass, Java would be in conflict as to what definition should be carried to MyClass and hence throws compilation error. | ||||
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Like Discuss Correct / Improve  default methods  java 8  multiple inheritance  object oriented programming (oops)  oops concepts  diamond problem   interfaces | ||||
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Ans. 1. Regulation / Enforcement / Policy / Contract , It's primary use 2. Use as a collection of utility methods(since java 8 through default methods) 3. Collecting constants together, As Interface are lighter, it makes sense to use them instead of classes if no getters and setters required. 4. Creation of Custom Annotations 5. Special services like marker interface | ||||
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Like Discuss Correct / Improve  interfaces   uses of interfaces in java Asked in 1 Companies | ||||
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Ans. Earlier any class implementing an interface was supposed to implement all methods declared in an interface. There was no place for optionally implementing all or subset of methods.Though we have abstract classes wherein we could have provided such a mechanism by declaring some methods as abstract while providing definition for some. But as Abstract classes have a body and are comparatively heavier than interfaces and interfaces associate closely to the concept of providing interfacing than abstract classes, Java might have though of providing optional implementation for default methods. This way same interface can be reused in variety of ways rather than making copies of an interface to suit different needs. | ||||
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Like Discuss Correct / Improve  java 8   java8  interface default methods  default methods Asked in 6 Companies | ||||
Very frequently asked in phone and walk in interviews. | ||||
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Ans. An interface without any method declaration is called as marker interface. there are 3 in-built interfaces in JVM i.e. serializable, clonable, remote | ||||
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Like Discuss Correct / Improve  java   oops   interfaces   marker interface   serializable   clonable Asked in 21 Companies intermediate   frequent | ||||
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Ans. No , it has run method declared. | ||||
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Like Discuss Correct / Improve  java   oops   interfaces   marker interface   runnable   yes-no | ||||
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Ans. With Java 9 we can declare interface methods as private | ||||
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Like Discuss Correct / Improve  java   oops   interfaces   yes-no   private | ||||
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Ans. Externalizable interface is used to write the state of an object into a byte stream in compressed format. | ||||
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Like Discuss Correct / Improve  java   oops   serialization   externalizable interface   interface Asked in 3 Companies | ||||
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Ans. Serializable is a marker interface whereas externalizable is not. | ||||
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Like Discuss Correct / Improve  java   oops   serialization   externalizable   interface   marker interface | ||||
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Ans. Keep it as a Abstract Class if its a "Is a" Relationsship and should do subset/all of the functionality. Keep it as Interface if its a "Should Do" relationship. | ||||
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Like Discuss Correct / Improve  java   oops   abstract classes   interfaces   advanced Asked in 3 Companies | ||||
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Ans. Collections class is a utility class having static methods for doing operations on objects of classes which implement the Collection interface. For example, Collections has methods for finding the max element in a Collection. | ||||
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Like Discuss Correct / Improve  java   collections   collections class   collection interface   basic interview question Asked in 6 Companies basic   frequent | ||||
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Ans. They just tell the compiler that the objects of the classes implementing the interfaces with no defined methods need to be treated differently. | ||||
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Ans. That would not be a problem as both are specifying the contract that implement class has to follow. If class C implement interface A & interface B then Class C thing I need to implement print() because of interface A then again Class think I need to implement print() again because of interface B, it sees that there is already a method called test() implemented so it's satisfied. | ||||
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Like Discuss Correct / Improve  java   oops   interfaces   multiple inheritance | ||||