Core Java - Interview Questions and Answers for 'Core Java' | Search Interview Question

Interview Questions and Answers - Order By Newest

Q941. Why use Java ?

^{This question was recently asked at 'Improwea'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q942. Why do we need ConcurrentHashMap ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q943. What is the default size of ArrayList ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q944. Find minimum operations required to convert one string to another. Allowed operation :Insertion Deletion Replace, all operational costs are same.

Core Java

Ans. StringBuilder str = new StringBuilder("Pizza");
int size = str.length();
str = str.replace(size-1, size, "u");
System.out.println("After replace, str = " str); // prints Pizzu

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q945. Write code to read data from a file and write it to a file with 2 threads using the thread name content

Core Java

^{This question was recently asked at 'verifone'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve threads file file handling Asked in 1 Companies}

Q946. What is the difference between Interfaces and Abstract Classes with respect to Java 8 ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q947. Which of the OOP's feature - encapsulation or abstraction - is more important ?

Core Java

Ans. Encapsulation facilitates security by hiding data and logic whereas Abstraction simplifies organization of data and related logic.

As applications scale, both concepts are required for easy management and maintenance. Encapsulation for security and criss cross communication between objects / modules will make it vulnerable. and Abstraction for better organization that enables better understanding of application code and easy maintainability.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve oops oops features oops concepts}

Q948. Which of the polymorphism type - static or runtime - is more important ?

Core Java

Ans. Method overloading / static polymorphism compared to method overriding / runtime polymorphism has very limited usage as it just opens up an alternate way of defining a different method with the same name.

Method Overriding on other hand opens up many other features like contracting , interfacing , pluging development and hence development of libraries and frameworks.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve oops oops features oops concepts}

Q949. What is the reason that non-static method are not allowed to be referenced from a static context in Java?

Core Java

Ans. If we try to access an instance method from a static context , the compiler has no way to guess which instance method ( variable for which object ), you are referring to. Though, you can always access it using an object reference.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q950. Which are the thread safe / synchronized / concurrent classes in java collections ?

Core Java

Ans. Stack
Properties
Vector
BlockingQueue
ConcurrentMap
ConcurrentNavigableMap

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve collections concurrent classes}

Q951. What are the differences between Intermediate and Terminal Operations in Java 8 streams?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q952. What is the difference between Collections.emptyList() and creating instance of a list ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q953. Which are the classes that implement java.util.List interface ?

Core Java

Ans. ArrayList
LinkedList
Vector
Stack

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q954. Why do you think that Stack collection class implement List interface ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q955. What is the there only one method declared in Runnable interface?

Core Java

Ans. The Runnable interface describes a class whose instances can be run as a thread. The interface itself is very simple, describing only one method ( run ) that is called automatically by Java when the thread is started. The Runnable interface is usually used in conjunction with the Thread class.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q956. What is difference between Executor.submit() and Executer.execute() method ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q957. What is difference between CyclicBarrier and CountDownLatch in Java ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q958. What do you mean by synchronized Non Access Modifier?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q959. Name few classes of java.util.regex package ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q960. Is String thread-safe?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q961. Explain toString method ? Which class contains this method ?

Core Java

^{This question was recently asked at 'NEC Technologies'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q962. Explain pre compilation.

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q963. What will the following code print and Why

class Class1 {
static{
System.out.println("Wow");
}
public static final int xyz=1;
}

class Class2{
public static void main(String[] args) {
System.out.println(String.valueOf(Class1.xyz));
}
}

Core Java

Ans. 1

Reason being that Class1.xyz is replaced with 1 during pre compilation only and a reference to Class1 is never made.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve static final pre compilation}

Q964. Why java allows explicit import of class final static elements but not others ?

Core Java

Ans. Because they can be replaced easily in pre compilation whereas others cannot.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q965. Why do we have multiple core java jars in java 9 ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java 9 java modules java 9 modules}

Q966. What is the concept of modules in Java 9 ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java 9 java modules java 9 modules}

Q967. How modules are different than packages in Java 9 ?

Core Java

Ans. Modules are independently build units and contains multiple packages.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java 9 java modules java 9 modules}

Q968. How Java 9 helps in building light weight applications ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java 9 java modules java 9 modules}

Q969. Do we need different class loaders for different modules in Java 9 ?

Core Java

Ans. No, We can use the same class loader.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java 9 java modules java 9 modules}

Q970. What is ModuleDescriptor ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java 9 java modules java 9 modules}

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.