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45+ Java Software Engineer Interview Questions And Answers

Java Programing ➔ Java Software Engineer Job Interview Questions and Answers

Java Software Engineer job interview preparation guide for freshers, professionals and experienced candidates. Explore list of Java Software Engineer frequently asked questions(FAQs) extracted from many real job interviews

★ Tell us why java is not 100% Object-oriented?
★ Tell us why do you need to use synchronized methods or blocks?
★ Explain me what is the difference between HashMap and ConcurrentHashMap?
★ Do you know why Java is platform independent?
★ Explain me when do you use volatile variables?
★ Explain me how are Annotations better than a Marker Interfaces?
★ Explain me what is singleton class and how can we make a class singleton?
★ Tell me what is the difference between an Iterator and a ListIterator?
★ Tell us what is the marker interface in Java?
★ Explain me how does the JVM handle storing local variables vs storing objects?
★ Do you know what is a Service?
★ Please explain and compare fail-fast and fail-safe iterators. Give examples?
★ Tell me why is the code printing true in the second and false in the first case?
★ Tell us what is the difference between equals() and == ?
★ Tell me what is reflection? Give an example of functionality that can only be implemented using reflection?
★ Tell me what is multiple inheritance? Is it supported by Java?
★ Please explain what is the ThreadLocal class? How and why would you use it?
★ Explain me why aren’t you allowed to extend more than one class in Java but are allowed to implement multiple interfaces?
★ As you know ArrayList, LinkedList, and Vector are all implementations of the List interface. Which of them is most efficient for adding and removing elements from the list? Explain your answer, including any other alternatives you may be aware of?
★ Explain me how can you catch an exception thrown by another thread in Java?
★ Tell me what are static initializers and when would you use them?
★ How to override a private or static method in Java?
★ Can you compare the sleep() and wait() methods in Java, including when and why you would use one vs. the other?
★ Tell us what is the Java Classloader? List and explain the purpose of the three types of class loaders?
★ Tell me public static void main(String args[])?
★ Explain me what is runtime polymorphism or dynamic method dispatch?
★ Explain me what is the difference between String s = "Test" and String s = new String("Test")? Which is better and why?
★ Explain me what does it mean for a collection to be “backed by” another? Give an example of when this property is useful?
★ Explain me what is the volatile keyword? How and why would you use it?
★ Tell us why would it be more secure to store sensitive data (such as a password, social security number, etc.) in a character array rather than in a String?
★ Can you give real world examples of when to use an ArrayList and when to use LinkedList?
★ int a = 1L;   won’t compile and int b = 0;   b += 1L;   compiles fine. Explain me why?
★ Explain me what is association?
★ Explain me what is method overloading and method overriding?
★ Can you explain me what is Polymorphism?
★ Tell us what are constructors in Java?
★ Tell us how can you swap the values of two numeric variables without using any other variables?
★ Tell us what are checked and unchecked exceptions? When do you use them?
★ Explain me when do you need to override the equals and hashCode methods in Java?
★ Tell me can an enum be extended?
★ Tell us what do you mean by aggregation?
★ Do you know what is the advantage of generic collection?
★ Explain me why doesn’t the following code generate a NullPointerException even when the instance is null?
★ Explain me what is a good usecase of calling System.gc()?
★ Do you know how threadsafe is enum in Java?

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