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

Interview Questions and Answers - Order By Rating

Q341. What are we doing here

list.stream().collect(Collectors.groupingBy(ClassA::getElement1,
Collectors.averagingDouble(ClassA::getelement2)));

Core Java

Ans. We are averaging elements of a collection by element1 grouped by element1

* list is the reference of collection
* element1 is the member element returned by getElement1 method of ClassA
* element2 is the member element returned by getElement2 method of ClassA

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

_{Like Discuss Correct / Improve java 8 collections java 8 streams collectors}

Q342. Can you explain following exception

java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.

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 ArithmeticException}

Q343. Write a program that count the number of access to a method?

Core Java

^{This question was recently asked at 'TrueCaller'.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}

Q344. What is a weak reference ?

Core Java

Ans. A weak reference is a reference that gets removed on the next garbage collection cycle.

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

_{Like Discuss Correct / Improve weak reference garbage collection Asked in 1 Companies rare}

Q345. What is the relation between classes in Java ?

Core Java

Ans. There are different types of relationship between classes

Inheritance - Also called is-a relationship, Child class object carries the body of the Parent class when initiated. Moreover there are certain privileges attach to method overriding to the classes related this way. This relationship exist for code reuse, method overriding and interfacing ( through abstract class ).

Composition - Also called has-a relationship. Class objects carries a reference to other class objects when instantiated. This relationship exist for work flow / work delegation.

Inner / Nested class - It’s a relationship that encapsulates the inner class or it’s object within the outer class. This relationship exist for encapsulation / security.

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

_{Like Discuss Correct / Improve}

Q346. What is the difference between implementing interfaces and inheritance 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}

Q347. Can we have a private default method ?

Core Java

Ans. No. The whole idea of default method is to provide a default definition in case the implementing class intend to provide definition for only some of the methods. Making any of the interface method private would restrict it from being implemented by the implementing class. So default method is an option to provide implementation and not restricting a new definition.

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

_{Like Discuss Correct / Improve java 9 default methods}

Q348. What could be the reason for allowing private methods in java 9 ?

Core Java

Ans. Java 8 allowed for method implementation using default methods in interfaces. As those default methods could contain complex logic and might need organizing the logic into multiple methods, they have allowed for private methods.

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

_{Like Discuss Correct / Improve java 9 default methods}

Q349. Can we have private methods in interfaces ?

Core Java

Ans. Yes, With Java 9

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

_{Like Discuss Correct / Improve java 9}

Q350. What is JShell?

Core Java

Ans. JShell is a feature in java 9 using which we can code and test without compiling using javac and see the result of calculations directly.

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

_{Like Discuss Correct / Improve jshell java 9}

Q351. How Java 9 would help resolve NoClassDefFoundError through it's modularity ?

Core Java

Ans. Java 9 would provide an error at compile time if there are different modules with the same package mapped to the same class loader and hence would provide a compile time check for this issue.

NoClassDefFoundError exists because of ambiguity at realtime because of multiple versions of same package / class exist. As Java 9 would provide a compile time check for it through clearly defined dependencies and exports and a check on duplicate packages being loaded by single class loader, it will fix the problem.

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

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

Q352. What is the default setting for Automatic modules regarding exporting packages and reading modules ?

Core Java

Ans. As one purpose of automatic module is to provide backward compatibility with the module less dependencies, automatic modules exports all packages and include all other modules.

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

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

Q353. How does Java 9 provides backward compatibility with libraries that haven't published themselves as modules ?

Core Java

Ans. Though Automatic modules. Any JAR on the module path without module descriptor ends up as automatic module

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

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

Q354. How does modularity in Java 9 facilitates better encapsulation ?

Core Java

Ans. By providing dependencies , services and exports explicitly

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

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

Q355. What are the qualified and unqualified packages ?

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 9 modules}

Q356. Does Java 9 allows same package within different modules ?

Core Java

Ans. Yes it allows if the modules are mapped to different class loaders.

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

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

Q357. What is the use of Requires, Exports, Opens and provides within Module Descriptor ?

Core Java

Ans. Requires specifies the dependencies for the module, i.e the modules required for this module to function.

Exports specifies the packages exported by the module.

Opens specifies the packages opened by the module.

Provides specifies the services provided by the module

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}

Q358. Difference between named and unnamed modules ?

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}

Q359. What is ModuleLayer ?

Core Java

Ans. A Module layer is created from a graph of modules and is a function that maps modules to their class loaders.

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}

Q360. 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}

Q361. 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}

Q362. 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}

Q363. 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}

Q364. 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}

Q365. 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}

Q366. 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}

Q367. 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}

Q368. 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}

Q369. 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}

Q370. 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}

Search Interview Questions

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