Nokia Janitor Interview Questions and Answers

Q1. Memory management in java 8
Ans. 
Java 8 introduced improvements in memory management with features like Metaspace and G1 garbage collector.
• Java 8 introduced Metaspace to replace the PermGen space for class metadata storage.

• G1 garbage collector in Java 8 improves garbage collection performance by dividing the heap into regions.

• Java 8 also introduced the concept of String deduplication to reduce memory usage for String objects.
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Q2. CQRS pattern in microservices
Ans. 
CQRS pattern separates read and write operations in microservices for better scalability and performance.
• CQRS stands for Command Query Responsibility Segregation

• It separates the read and write operations in microservices

• Write operations update the data, while read operations retrieve the data

• Helps in improving scalability and performance by optimizing for each operation type
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Basic aptitude test and basic coding questions like arrays and strings

Q1. How to pull the large amount of data in spring data jpa
Ans. 
To pull large amount of data in Spring Data JPA, use pagination, lazy loading, and query optimization techniques.
• Use pagination to limit the amount of data retrieved in each query

• Implement lazy loading to fetch data only when needed

• Optimize queries by using indexes, avoiding N+1 query problem, and fetching only necessary columns
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Q2. Write singleton class
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Singleton class ensures only one instance of a class is created and provides a global point of access to it.
• Create a private static instance of the class

• Provide a private constructor to prevent instantiation

• Create a public static method to access the instance
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Q1. Difference btwn jdk , jre and jvm
Ans. 
JDK is a development kit that includes JRE and tools for developing Java applications. JRE is a runtime environment for executing Java programs. JVM is a virtual machine that runs Java bytecode.
• JDK (Java Development Kit) includes JRE (Java Runtime Environment) and development tools like compiler and debugger.

• JRE (Java Runtime Environment) is a software package that provides the libraries and components necessary for ru...read more
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Q2. Difference btwn static and volatile
Ans. 
Static variables are shared among all instances of a class, while volatile variables are used to indicate that a variable's value will be modified by different threads.
• Static variables are initialized only once at the start of the program and retain their value throughout the program's execution.

• Volatile variables are used to ensure visibility of changes to variables across multiple threads.

• Static variables are accesse...read more
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Q3. What is final keyword
Ans. 
Final keyword is used in Java to declare constants, prevent method overriding, and prevent class inheritance.
• Used to declare constants - value cannot be changed once assigned

• Prevents method overriding - method cannot be overridden in child classes

• Prevents class inheritance - class cannot be extended
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Q4. Difference btwn paralle stream and stream
Ans. 
Parallel stream allows processing elements concurrently, while stream processes elements sequentially.
• Parallel stream can improve performance by utilizing multiple threads for processing.

• Stream processes elements one by one in a sequential manner.

• Example: stream().parallel() vs stream().sequential()
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Q5. What is stream used for
Ans. 
Streams are used in Java to process collections of objects in a functional style.
• Streams allow for concise and readable code when working with collections.

• They support operations like filter, map, reduce, and collect.

• Streams can be sequential or parallel, depending on the processing requirements.

• Example: List names = Arrays.asList("Alice", "Bob", "Charlie"); names.stream().filter(name -> name.startsWith("A")).forEach(S
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Java take home assignment

Q1. Discussing coding assignment
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Q1. Asking related to java, and good knowledge of Oops concepts
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Q2. Basic java program
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Q1. Asking past project and technology that you are using
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Q2. API related question like rest, sop
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Mcqs was good was reasonable covered h=java

Q1. Technical round
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Q1. Hr round was good
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