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

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Q601. What are the different ways to create objects in Java ?

Core Java

Ans. 1. Using new operator
3. Using Class.forName or Reflection
4. Using clone
5. Using Deserialization

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Q602. Can we create object in static block ?

Core Java

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Q603. Can you tell me any 10 unix command you have worked with ?

Unix

Ans. grep, ls, kill, vi , scp , wget,telnet, zip, unzip,mv,cp

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Q604. Implement a Stack with 2 threads in which one thread push data and another pop data.

Data Structure

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Q605. What are the 7 OSI LAYERS ?

Networking

Ans. Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical

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Q606. Does it make sense to mock integration calls during stress / load test ?

Testing

Ans. No, its usually not done.

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Q607. Explain servlet lifecycle

Java EE

Ans. Init -> service -> destroy.

Out of these, init and destroy are called once per servlet whereas service is called every time when a request is made to the servlet.

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Q608. Explain Hibernate caching mechanism

Hibernate

Ans. Every fresh session having its own cache memory, Caching is a mechanism for storing the loaded objects into cache memory. The advantage of cache mechanism is, whenever again we want to load the same object from the database then instead of hitting the database once again, it loads from the local cache memory only, so that the no. of round trips between an application and a database server got decreased. It means caching mechanism increases the performance of the application.

In hibernate we have two levels of caching

First Level Cache [ or ] Session Cache
Second Level Cache [ or ] Session Factory Cache [ or ] JVM Level Cache

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Q609. What is XSS or Cross site scripting ?

Security

Ans. XSS or cross site scripting is a javascript vulnerability in web applications. The easiest way to explain this is with a case when the user enters a script in the client side input fields and that input gets processed without getting validated. This leads to untrusted data getting saved and executed on the client side.

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Q610. in the following class:
class A {
void methoda(Object o) {
Sysout("Object");
}

void methoda(String s) {
Sysout("String");
}

public static void main(String []args) {
A a = new A();
a.methoda(null);
}
}

what will be printed?

Core Java

Ans. String

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Q611. How many read and write operations are provided at the same time by ConcurrentHashMaps ?

Core Java

Ans. ConcurrentHashMaps provide unlimited read operation fro multi threaded environment. For write operation only one thread can change value for particular segment of map.

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Q612. what is volatile and atomic

Core Java

Ans. When you declare a member/variable as volatile, you are forcing threads to read values from main memory instead of thread memory.

When you declare as atomic, the read and update/write operations are performed as a single unit. A lock is acquired during atomic operation.

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Q613. Difference between indexing and partioning

Database

Ans. Creating an index creates a separate table. ... Indexes are used to speed the search of data within tables. Partitions provide segregation of the data at the hdfs level, creating sub-directories for each partition. Partitioning allows the number of files read and amount of data searched in a query to be limited

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Q614. serialization and deserialization of singleton class

Core Java

Ans. The problem with serialized singleton class is that whenever we deserialize it, it will create a new instance of the class. To overcome this scenario all we need to do is to provide the implementation of readResolve() method.

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Q615. Detect a loop in a linked list

Data Structure

Ans. Work with two pointers on the linked list - a slow pointer (increments by one node) and a fast pointer (increments by two nodes). If both of these pointers meet at the same node, then there is a cycle in the linked list. Otherwise, no cycle.

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Q616. There are 8 balls, 7 weigh 100 gms, 1 is defective, there is a weighing scale, any number of balls can be measured at the same time. in how many attempts defective balls can be found out.

Puzzle

Ans. 2 attempts Weigh 3 3 balls. If the weight is same then weigh the remaining two balls

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Q617. Can a double value be cast to a byte ?

Core Java

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Q618. How do you convert List to Array ?

Core Java

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Q619. Explain briefly about Queue Interface ?

Core Java

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Q620. What is strictfp Modifier?

Core Java

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Q621. What is the Main Advantage of the native Key Word?

Core Java

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Q622. What is @EnableSptringMVC ?

Spring

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Q623. What is doCallRealMethod() method used for ?

PowerMock

Ans. When we Mock an object and then make a reference to any method using mocked object reference , java never makes a call to that method and looks for mocked value to be returned or null if none specified. But If we want that to be overridden and want java to make actual method call upon using mocked object reference, this method can be used.

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Q624. What does the following code

MockitoAnnotations.initMocks(this);

Mockito

Ans. Initializes objects annotated with Mockito annotations

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Q625. How can you verify if there were interactions with a static method using PowerMock ?

PowerMock

Ans. We can use PowerMockito.verifyStatic for this purpose

PowerMockito.verifyStatic(VerificationModeFactory.times(1));
<Class_Name>.<static_method_name>;

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Q626. Have you ever used PowerMock ? If yes , which mocking framework you have used it with ?

PowerMock

Ans. Yes, I have used PowerMockito with Mockito.

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Q627. Explain hibernate associations.

Hibernate

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Q628. Why is Java platform independent ?

Core Java

Ans. Platform independent language means once compiled you can execute the program on any platform (OS). Java is platform independent. Because the Java compiler converts the source code to bytecode, which is Intermediate Language. Bytecode can be executed on any platform (OS) using JVM( Java Virtual Machine).

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Q629. What is DDOS attack ?

Security

Ans. DDOS is denial of service attack in which the hacker seeks to make a machine or resource unavailable to its expected users by disrupting services.

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Q630. What is the difference between the 'A' and "A" in Java ?

Core Java

Ans. 'A' is a character whereas "A" is a String.

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