Deloitte Java Developer Interview Questions, Process, and Tips

HashMap is a data structure in Java that stores key-value pairs and allows fast retrieval of values based on keys.

• HashMap implements the Map interface in Java

• It allows null keys and values

• Keys in a HashMap must be unique

• Example: HashMap map = new HashMap<>()

HashMap is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values.

• HashMap internally uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to determine the index in the array where it will be stored.

• If multiple keys hash to the same index, a linked list is used to handle collisions.

• HashMap uses the hashCode() method of keys to calc...read more

Throw is used to explicitly throw an exception in a method, while Throws is used to declare the exceptions that a method may throw.

• Throw is used within a method to throw an exception explicitly.

• Throws is used in the method signature to declare the exceptions that the method may throw.

• Throw is followed by an instance of Throwable class, while Throws is followed by the exception class names separated by commas.

• Example: t...read more

Arrays are fixed in size, while ArrayLists can dynamically resize. ArrayLists provide more flexibility and functionality.

• Arrays have a fixed size, while ArrayLists can dynamically resize.

• ArrayLists can easily add, remove, or modify elements, while arrays require manual shifting of elements.

• Arrays use [] syntax for declaration and initialization, while ArrayLists use the ArrayList class from the Java Collections framewo

ArrayList is resizable array implementation, LinkedList is doubly linked list implementation, Vector is synchronized version of ArrayList.

• ArrayList is faster for accessing elements, LinkedList is faster for adding/removing elements in middle.

• ArrayList uses less memory than LinkedList due to contiguous memory allocation.

• Vector is thread-safe but slower than ArrayList due to synchronization overhead.

Iterate through a hashmap using an iterator in Java

• Create an iterator using the entrySet() method of the hashmap

• Use a while loop to iterate through the hashmap entries

• Access the key and value of each entry using the getKey() and getValue() methods

Java SOLID principles are a set of design principles that help in creating maintainable and scalable software.

• S - Single Responsibility Principle: A class should have only one reason to change.

• O - Open/Closed Principle: Software entities should be open for extension but closed for modification.

• L - Liskov Substitution Principle: Subtypes must be substitutable for their base types.

• I - Interface Segregation Principle: Cli...read more

HashMap is an implementation of Map interface that stores key-value pairs using a hash table.

• HashMap uses hashing to store and retrieve elements.

• It uses an array of linked lists to handle collisions.

• The hash code of the key is used to determine the index of the array.

• If multiple keys have the same hash code, they are stored in the same linked list.

• When retrieving a value, the hash code is used to find the correct linke...read more