Xyz Company Java Developer Interview Questions and Answers

Q1. Stringbuilder and string buffer diff
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Q2. Where we store the object of string
Ans. 
Objects of String are stored in the String Pool in Java.
• String objects are stored in the String Pool, a special memory area in Java heap memory.

• String literals are automatically stored in the String Pool.

• String objects created using the new keyword are not stored in the String Pool.

• String.intern() method can be used to store a String object in the String Pool.
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Q3. What is bean in springboot
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A bean in Spring Boot is a Java object that is instantiated, assembled, and managed by the Spring IoC container.
• Beans are defined in the Spring configuration file or using annotations like @Component, @Service, @Repository, etc.

• Beans are singleton by default but can be scoped as prototype, request, session, etc.

• Beans are injected into other beans using dependency injection.

• Example: @Component annotation is used to defi
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Q4. What is query parameters and path param
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Query parameters are used to pass data to a web server through the URL, while path parameters are part of the URL itself.
• Query parameters are key-value pairs added to the end of a URL after a '?'

• Path parameters are variables within the URL path itself, denoted by curly braces {}

• Example of query parameter: www.example.com/api/users?id=123

• Example of path parameter: www.example.com/api/users/{userId}
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Q5. Code snippet related to exception
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Q6. Diff between exception and error
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Exceptions are recoverable errors that can be handled in code, while errors are unrecoverable issues that usually result in program termination.
• Exceptions are checked at compile time, while errors are unchecked.

• Exceptions are subclasses of Throwable, while errors are subclasses of Error.

• Examples of exceptions include FileNotFoundException, NullPointerException, while examples of errors include OutOfMemoryError, StackOv
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Q1. Quick sort - keep order same
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Q2. Reverse string with spaces but keep the space position intact
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Reverse a string while keeping the position of spaces intact
• Split the string into an array of characters

• Iterate through the array and reverse the characters while keeping track of space positions

• Join the array back into a string
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Q1. Ask to write code for equal and hashcode in notepad
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Q2. Type of Collections and its internal working
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Java collections are data structures that store and manipulate groups of objects.
• Types of collections include List, Set, Map, Queue, etc.

• Internal workings involve data structures like arrays, linked lists, hash tables, etc.

• Collections framework provides interfaces and classes for working with collections.
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Q3. Count number of occurrence of string from Array
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Count occurrences of a specific string in an array of strings.
• Iterate through the array and use a HashMap to store the count of each string.

• Use the string as key and increment the count each time it is encountered.

• Return the count of the specific string at the end.
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Q4. Write a code using stream
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Using stream to filter a list of strings
• Use the filter method to apply a predicate to each element in the stream

• Convert the stream back to a list using the collect method
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Q1. What are checked and unchecked exceptions?
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Checked exceptions are exceptions that must be either caught or declared in the method signature, while unchecked exceptions do not need to be caught or declared.
• Checked exceptions are subclasses of Exception class, excluding RuntimeException and Error.

• Checked exceptions are checked at compile time, so the compiler forces the programmer to handle them.

• Unchecked exceptions are subclasses of RuntimeException and Error cl...read more
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Q2. What is the difference between Spring and SpringBoot?
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Spring is a framework for building Java applications, while SpringBoot is a tool that simplifies the setup and configuration of Spring applications.
• Spring is a comprehensive framework that provides various modules for different functionalities like dependency injection, aspect-oriented programming, etc.

• SpringBoot is an opinionated tool that simplifies the setup and configuration of Spring applications by providing defa...read more
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Q1. Java 8 features, functional Interfaces and predefined functional interfaces, Streams
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Q2. Collections, Aggregations, solid principles in Java
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Q3. Design patterns, singleton and factory explain in detail
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Design patterns are reusable solutions to common problems in software design. Singleton ensures a class has only one instance, while factory creates objects without specifying the exact class.
• Design patterns are best practices for solving common software design problems.

• Singleton pattern ensures a class has only one instance and provides a global point of access to it.

• Factory pattern creates objects without specifying ...read more
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Q4. Spring functions, Spring Runners, Spring Exception handling
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Q5. Springboot annotations except common(any 5)
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Q6. Write spring boot program to accept json as request. write the logic and explain
Ans. 
Create a Spring Boot program to accept JSON requests and process the data.
• Create a Spring Boot application with a REST controller to handle incoming JSON requests.

• Use @PostMapping annotation to map the endpoint for accepting JSON requests.

• Use @RequestBody annotation to bind the incoming JSON data to a Java object.

• Process the JSON data as needed in the controller method.

• Return a response as JSON if required.
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3 coding questions were given and to be solved only in java