IDBI Intech Limited Java Developer Interview Questions, Process, and Tips

There are multiple ways to iterate over a HashMap in Java.

• Using keySet() and values() methods

• Using entrySet() method

• Using forEach() method with lambda expression

Method overriding in Java with code example

• Output will be 'Child class method' as the method in Child class overrides the method in Parent class

• Method overriding is a feature that allows a subclass to provide a specific implementation of a method that is already provided by its superclass

• The method in the subclass should have the same name, return type, and parameters as the method in the superclass

API to save data in Java

• Use HTTP POST method to send data to the server

• Create a RESTful endpoint to handle the data saving

• Validate the input data before saving it to the database

ArrayList is implemented as a resizable array, while LinkedList is implemented as a doubly linked list.

• ArrayList provides fast random access, LinkedList provides fast insertion and deletion.

• ArrayList uses more memory as it needs to allocate a fixed size array, LinkedList uses more memory for storing references to the next and previous elements.

• Example: ArrayList is better for scenarios where random access is required, ...read more

HashMap is non-synchronized and allows null values, while HashTable is synchronized and does not allow null values.

• HashMap is non-synchronized, meaning it is not thread-safe, while HashTable is synchronized and thread-safe.

• HashMap allows null values for both keys and values, while HashTable does not allow null keys or values.

• HashMap is faster than HashTable as it is non-synchronized, but HashTable is preferred in multi...read more

The contract between hashCode and equals method is that if two objects are equal according to the equals method, then their hash codes must also be equal.

• hashCode and equals method must be consistent - if two objects are equal according to equals method, their hash codes must be equal

• If two objects have the same hash code, they may or may not be equal according to equals method

• Overriding equals method in a class requir...read more

Java 8 introduced several new features including lambda expressions, functional interfaces, streams, and default methods in interfaces.

• Lambda expressions allow you to pass functions as arguments.

• Functional interfaces have a single abstract method and can be used with lambda expressions.

• Streams provide a way to work with sequences of elements.

• Default methods allow interfaces to have method implementations.

Ways to start a thread in Java

• Extending the Thread class and overriding the run() method

• Implementing the Runnable interface and passing it to a Thread object

• Using a thread pool from the Executors class

The thread will continue running as it is already active

• The thread will not be started again if it is already running

• Attempting to start a thread that is already running will not have any effect

• The thread will continue its execution without any interruption

Join method is used to wait for a thread to finish its execution, while sleep method is used to pause the execution of a thread for a specified amount of time.

• Join method is used to wait for a thread to finish its execution before moving on to the next task.

• Sleep method is used to pause the execution of a thread for a specified amount of time, allowing other threads to run.

• Example: thread1.join() will wait for thread1 ...read more

Microservices can introduce complexity, communication overhead, and potential performance issues.

• Increased complexity due to managing multiple services

• Communication overhead between services

• Potential performance issues due to network latency

• Difficulty in maintaining consistency across services

No, @FunctionalInterface cannot be extended. Map and flatMap are default methods in the interface and cannot be overridden.

• No, @FunctionalInterface cannot be extended as it is a single abstract method interface.

• Map and flatMap are default methods in the interface and cannot be overridden.

• Example: public interface MyInterface { void myMethod(); default void myDefaultMethod() { // implementation } }

Using Java8 to filter vowels from an array of strings

• Use Java8 stream and filter to iterate through each string in the array

• Use a lambda expression to check if each character is a vowel

• Collect the filtered strings into a new array