30+ Weatherford Interview Questions and Answers

To make a class immutable in Java, we need to follow certain guidelines.

• Make the class final

• Make all fields private and final

• Do not provide setter methods

• If the field is mutable, return a clone of it instead of the original object

• Ensure that any mutable objects passed to the constructor are not modified outside the class

Autoboxing is the automatic conversion of primitive data types to their corresponding object wrapper classes.

• Autoboxing is useful when working with collections that require objects instead of primitives.

• Example: int i = 5; Integer j = i; //autoboxing

• Unboxing is the opposite of autoboxing, where an object of a wrapper class is converted back to its corresponding primitive type.

• Example: Integer j = 5; int i = j; //unboxing

Program to add numbers in harmonic series (1+1/2+1/3+...+1/n)

• Create a variable to store the sum

• Use a loop to iterate through the series up to n

• Add each term to the sum

• Print the sum

finally is used to execute a block of code after try-catch block, while static block is executed when class is loaded.

• finally block is used to perform cleanup operations like closing database connections, file streams etc.

• static block is used to initialize static variables or perform any other static initialization.

• finally block is always executed whether an exception is thrown or not, while static block is executed only once when class is loaded.

• finally block is always writt...read more

ArrayList and Vector are similar but Vector is synchronized while HashMap and HashTable are both key-value pair data structures but HashTable is synchronized.

• ArrayList and Vector both implement List interface but Vector is thread-safe while ArrayList is not.

• Vector is slower than ArrayList due to synchronization.

• HashMap and HashTable both store key-value pairs but HashTable is thread-safe while HashMap is not.

• HashMap allows null keys and values while HashTable does not.

• HashMap...read more

Typecasting up and down refers to converting a variable of one data type to another data type of higher or lower precision.

• Typecasting up involves converting a variable of lower precision to a variable of higher precision, such as converting an int to a double.

• Typecasting down involves converting a variable of higher precision to a variable of lower precision, such as converting a double to an int.

• Typecasting can result in loss of data or precision.

• Typecasting can be done imp...read more

Java 8 introduced new features like lambda expressions, functional interfaces, streams, and default methods.

• Lambda expressions allow you to write code in a more concise and readable way.

• Functional interfaces provide a single abstract method for functional programming.

• Streams enable processing sequences of elements in a functional style.

• Default methods allow interfaces to have method implementations.

• Example: Lambda expression - (a, b) -> a + b

• Example: Functional interface - Co...read more

Collections are data structures that store and manipulate groups of objects.

• Collections provide a way to manage and manipulate groups of objects

• Java provides several built-in collection classes such as ArrayList, LinkedList, HashSet, etc.

• Collections can be used to perform operations like searching, sorting, filtering, etc.

• Collections can store objects of any type, including primitive types and user-defined classes

The @Autowired annotation in Spring is used to automatically wire dependencies into a bean.

• It eliminates the need for manual wiring of dependencies

• It can be used to inject dependencies into constructors, fields, and methods

• It can be used with other annotations like @Qualifier and @Value

• It can be used with both XML and Java-based configurations

Use the Strategy design pattern for complex design.

• Strategy pattern allows you to define a family of algorithms, encapsulate each one, and make them interchangeable.

• It helps in separating the behavior of a class from the class itself, making it easier to switch between different algorithms at runtime.

• Examples of using Strategy pattern include implementing different sorting algorithms in a class or defining various payment methods in an e-commerce application.

To iterate a map in Java, use a for-each loop or an iterator.

• Use the entrySet() method to get a set of key-value pairs

• For-each loop: for(Map.Entry entry : map.entrySet())

• Iterator: Iterator> iterator = map.entrySet().iterator();

• Use hasNext() and next() methods to iterate through the map

Types of synchronization in Java

• Synchronized methods

• Synchronized statements

• ReentrantLock

• Semaphore

• CountDownLatch

OOPS stands for Object-Oriented Programming System. It is a programming paradigm based on the concept of objects.

• OOPS is based on four main concepts: Encapsulation, Inheritance, Polymorphism, and Abstraction.

• Encapsulation is the process of hiding the implementation details of an object from the outside world.

• Inheritance allows a class to inherit properties and methods from another class.

• Polymorphism allows objects of different classes to be treated as if they were of the same...read more

Access modifiers in method overriding

• Access modifiers in the overriding method cannot be more restrictive than the overridden method

• The access modifier can be less restrictive or the same as the overridden method

• Private methods cannot be overridden

• Examples: public method can be overridden by public or protected method, but not by private method

JVM stands for Java Virtual Machine, which is an abstract computing machine that enables a computer to run Java programs. JIT stands for Just-In-Time compiler, which compiles Java bytecode into native machine code at runtime for improved performance.

• JVM is responsible for executing Java programs by converting Java bytecode into machine code that can be understood by the computer's operating system.

• JIT is a component of the JVM that improves the performance of Java application...read more

Rest Api is a web service that uses HTTP methods to access and manipulate data.

• Rest stands for Representational State Transfer

• It is an architectural style for building web services

• Uses HTTP methods like GET, POST, PUT, DELETE

• Data is transferred in JSON or XML format

• Examples: Twitter API, Facebook Graph API

Map applies a function to each element in a stream, while flatMap applies a function that returns a stream for each element.

• Map transforms each element in a stream using a function, returning a new stream of transformed elements.

• FlatMap transforms each element in a stream using a function that returns a stream, then flattens the streams into a single stream.

• Volatile keyword in Java is used to indicate that a variable's value will be modified by different threads.

Create a REST service using Spring Boot

• Create a new Spring Boot project

• Add dependencies for Spring Web and Spring Boot DevTools in pom.xml

• Create a new Java class for the REST controller with @RestController annotation

• Define request mapping annotations like @GetMapping, @PostMapping, @PutMapping, @DeleteMapping for different HTTP methods

• Implement the business logic for each endpoint

• Run the Spring Boot application and test the REST service using tools like Postman

Spring Actuator is a feature in Spring Boot that provides monitoring and management capabilities for your application.

• Spring Actuator exposes various endpoints to monitor and manage your application, such as /health, /info, /metrics, etc.

• It allows you to check the health of your application, gather metrics, view application properties, and more.

• You can also create custom endpoints for specific monitoring needs.

• Spring Actuator is commonly used in production environments to mon...read more

SDLC stands for Software Development Life Cycle, which consists of different phases from planning to maintenance.

• 1. Planning phase involves defining project scope, requirements, and creating a project plan.

• 2. Analysis phase focuses on gathering and analyzing requirements to create a detailed system design.

• 3. Design phase involves creating a high-level design, detailed design, and architecture for the software.

• 4. Implementation phase is where the actual coding and development ...read more

Callable is used to return a result and can throw checked exceptions, while Runnable is used for void operations.

• Callable can return a result and throw checked exceptions, while Runnable cannot.

• Callable is a functional interface with a method call() that returns a result, while Runnable is a functional interface with a method run() that does not return a result.

• Example: Callable task = () -> { return 5 + 3; }; Runnable task = () -> { System.out.println("Hello World!"); };

The 4 pillars of data structure are arrays, linked lists, stacks, and queues.

• Arrays: Data structure that stores a collection of elements with a fixed size.

• Linked Lists: Data structure where each element points to the next element in the sequence.

• Stacks: Data structure that follows the Last In First Out (LIFO) principle.

• Queues: Data structure that follows the First In First Out (FIFO) principle.

Spring is a framework for building Java applications, while Spring Boot is a tool for quickly creating standalone Spring-based applications.

• Spring is a comprehensive framework for building Java applications, providing support for various modules like Spring MVC, Spring Security, and Spring Data.

• Spring Boot is a tool that simplifies the process of setting up and configuring a Spring application, by providing defaults and auto-configuration.

• Spring Boot includes embedded servers...read more

Annotations in Spring Boot are used to provide metadata about the application and its components.

• Annotations are used to configure Spring Boot applications, define beans, handle requests, etc.

• Examples include @RestController, @Autowired, @RequestMapping, @Component, etc.

Streams in Java are sequences of elements that support functional-style operations.

• Streams allow for processing sequences of elements in a functional style.

• They can be created from various data sources like collections, arrays, or I/O channels.

• Operations on streams can be intermediate (e.g. filter, map) or terminal (e.g. forEach, collect).

• Streams promote parallel processing and lazy evaluation for improved performance.

• Example: List names = Arrays.asList("Alice", "Bob", "Charl...read more