Persistent Systems Senior Java Developer Interview Questions and Answers

Q1. Comparable and comparator
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Q2. Singleton class
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Q3. Springboot questions were asked
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Q4. Java class loader
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Q5. Java 8 coding questions
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There were MCQ questions consists of different sections like Design Pattern,Java 8

Q1. Questions related to Multithreading,Design patterns
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Q2. Java coding questions
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Q1. Questions related to Multithreading
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Q2. Java coding questions
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Q1. Java 8, exception handling for method overriding, collections basic on HashMap , hash set, blocking queue. Transient volatile
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Q1. What is Executer Service?
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ExecutorService is an interface in Java that provides a way to manage and control the execution of threads in a multithreaded environment.
• It is part of the java.util.concurrent package.

• It provides methods to submit tasks for execution, manage thread pools, and control the execution of tasks.

• It allows for the execution of tasks asynchronously and provides features like scheduling, cancellation, and monitoring of tasks.

• E...read more
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Q2. What is the use of JPA?
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JPA is a Java specification for mapping Java objects to relational databases.
• JPA stands for Java Persistence API

• It provides a way to map Java objects to database tables and vice versa

• JPA simplifies the development of data access layer in Java applications

• It supports object-relational mapping (ORM) and allows developers to work with entities, relationships, and queries in a more object-oriented way
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Q3. Explain about PreparedStatement
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PreparedStatement is used in Java to execute parameterized SQL queries to prevent SQL injection attacks.
• PreparedStatement is a subinterface of Statement in Java.

• It is used to execute parameterized SQL queries.

• It helps prevent SQL injection attacks by automatically escaping special characters.

• Example: PreparedStatement pstmt = connection.prepareStatement("SELECT * FROM users WHERE username = ?");
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Q4. Program to find the missing numbers from Array
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Program to find missing numbers from Array
• Iterate through the array and store each number in a HashSet

• Then iterate from 1 to the length of the array and check if each number exists in the HashSet

• If a number is not found in the HashSet, it is a missing number
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Q1. Write a spring boot rest controller
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A Spring Boot REST controller is used to handle incoming HTTP requests and return appropriate responses.
• Create a new Java class annotated with @RestController

• Define request mapping annotations like @GetMapping, @PostMapping, @PutMapping, @DeleteMapping

• Inject dependencies using @Autowired annotation

• Return response using ResponseEntity or directly as method return value
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Q2. Write a code for get a reverse String having a comma separated value in java
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Code to reverse a comma separated string in Java
• Split the input string by comma to get an array of strings

• Iterate through the array in reverse order and append each element to a new string with a comma

• Return the reversed comma separated string
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Q1. Java Springboot Microservices
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Q1. Questions on Java spring AWS and Kafka
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Q1. Current salary? Expected salary?
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