Java / Interface

Can we initialize Optional value as null in Java8?

Yes, but its a bad practice. The main intention of Optional is to eliminate null referencing.

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Inner Interface in Java. Can an interface inherit/extend multiple interface? What is a Marker(Tag) Interface? Can an Interface implement another interface? Are interfaces also inherited from Object class? Can a class be defined inside an Interface? Example of a nested interface from Java API. What are the access modifiers applicable for the nested interface declared inside a class? Advantages of Inner Interface. Are Nested interfaces declared static? can we have non-static inner interface? Syntax for inner interface. Should the nested interface must be public? Can we define a class inside an interface? Advantage of having a class inside an interface. What is the difference between an Abstract class and Interface? Can a method inside a Interface be declared as final or static in Java? Can an Interface extend another Interface? Why interface is allowed to extend multiple interface whereas class can inherit only one class? Can an Interface be final? Give few examples of a marker interface? Can I define private and protected variables in an interface? What is Externalizable? Difference between Serializable and Externalizable. Does Externalizable extends Serializable interface? Can you specify the accessibility modifier for methods inside an interface? What is abstract Interfaces in Java? Can a interface define static initializer in Java ? What is functional interface in Java 8. Why do we implement interfaces in Java? What are the rules for writing lambda expressions in Java 8? What is SAM interface in Java 8? How will you call a default method of an interface in a class? Explain type inference in Java 8. Explain the difference between lambda expression and anonymous class in terms of this reference. What is Optional in Java8? Can we initialize Optional value as null in Java8? Difference between Optional flatMap() and map() in Java8. Does interface uses all Object class methods? Can interface have instance fields? Can interface have instance method? How JVM invoke special behavior in case of marker interface? How to write your own marker interface? Can we have private interface method? Can an interface have main method? Can you modify the value of an interface field? Can we have private method/static method in Interface ?

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OOPS Concepts and its implementation in Java 19 Inheritance 29 JDK, JRE, JVM, JIT 69 Java Identifiers 4 Object, Class and Package 44 Variable 9 Local Variables 6 Instance Variables (Non Static Variables) 3 Class Variables (Static Variables) 13 Package 10 Operators 9 Modifiers 29 Data types 10 Methods 39 Control Statements 14 Access Modifiers 5 Constructor 38 Interface 46 Abstract Class 19 Enum 20 Arrays 20 Strings 32 Using String 29 Exception 55 Collections 56 List and its implementations 22 Map and its implementations 39 Set and its implementations 23 Queue and its implementations 4 Regular expressions 3 Design Patterns 75 Generics 20 Casting 5 volatile 13 Java ThreadLocal 10 Java Multithreading 113 Java Multithreading part II 18 final keyword 13 static keyword 16 Java Transactions (JTA) 21 Concurrent collections 55 Java Serialization 36 JDBC 53 JNDI 17 RMI 6 JAXB 10 JMS 45 JMX 9 Servlet Interview Questions 16 log4j 19 Annotations 10 XML 14 Garbage collection 31 Programs 8 JVM 4 Java8 streams 34 JavaFX 6 Autosys Interview questions 21 The Java Virtual Machine: How and What Is It Used For? Java 11 10 Java 12 5 Top Errors You Should Avoid when Studying Programming Java 17 1 JPMS 6 Java Record Keyword 4 MapStruct Java Interview questions Java 21 Interview Questions 46 Lombok Interview questions 48 Quarkus Interview questions 50

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