10+ Abbott Interview Questions and Answers

JVM, JRE, and JDK are essential components of Java development, with JVM executing Java programs, JRE providing libraries and tools, and JDK including JRE along with development tools.

• JVM (Java Virtual Machine) is responsible for executing Java programs by converting bytecode into machine code.

• JRE (Java Runtime Environment) includes JVM, libraries, and other necessary components to run Java applications.

• JDK (Java Development Kit) contains JRE along with development tools like...read more

Query to fetch data of employees with salary greater than 50,000

• Use SELECT statement to retrieve data

• Add WHERE clause with salary condition

• Example: SELECT * FROM employees WHERE salary > 50000;

The Object class is the root class for all Java classes and provides common methods for all objects.

• The Object class is located in the java.lang package.

• It provides methods such as equals(), hashCode(), and toString() which can be overridden in subclasses.

• All classes in Java are directly or indirectly derived from the Object class.

• Example: String class in Java extends the Object class.

No, multiple try blocks are needed for handling different exceptions.

• Multiple try blocks are needed to handle different types of exceptions separately.

• Each try block can have its own catch block to handle specific exceptions.

• Using a single try block for all exceptions can lead to confusion and improper handling.

HashMap is a key-value pair collection while HashSet is a collection of unique elements.

• HashMap allows duplicate values but keys must be unique.

• HashSet does not allow duplicate elements.

• HashMap uses key-value pairs for storing data, while HashSet only stores individual elements.

• Example: HashMap<String, Integer> map = new HashMap<>(); HashSet<String> set = new HashSet<>();

String is immutable, StringBuffer is synchronized, StringBuilder is not synchronized.

• Use String when the value will not change frequently.

• Use StringBuffer when multiple threads will be modifying the same String.

• Use StringBuilder when single-threaded and frequent modifications are needed.

Java uses automatic memory management through garbage collection to allocate and deallocate memory for objects.

• Java uses garbage collection to automatically manage memory by deallocating memory for objects that are no longer in use.

• Memory is divided into two main areas: stack memory for method calls and local variables, and heap memory for objects.

• Objects are created on the heap memory using the 'new' keyword, and memory is automatically deallocated when the object is no long...read more

Threads can be utilized within a class by extending the Thread class or implementing the Runnable interface.

• Create a class that extends Thread or implements Runnable interface

• Override the run() method to define the task to be executed in a separate thread

• Instantiate the class and start the thread using start() method

Exception handling in Java is a mechanism to handle runtime errors and prevent program crashes.

• Exceptions are objects that represent errors or unexpected events in a program.

• Java provides try-catch blocks to handle exceptions and prevent program termination.

• Common exceptions in Java include NullPointerException, ArrayIndexOutOfBoundsException, and IOException.

• Developers can create custom exceptions by extending the Exception class.

• Using finally block ensures that certain code...read more

String pool is a storage area in memory where strings are stored to optimize memory usage by reusing common string literals.

• String pool is a part of the Java heap memory where unique string literals are stored.

• Strings in the pool are shared among multiple variables to save memory.

• When a new string is created, Java first checks if it already exists in the pool before creating a new instance.

• Example: String str1 = "hello"; String str2 = "hello"; Both str1 and str2 point to the ...read more

A hash map is a data structure that stores key-value pairs and uses a hash function to map keys to their corresponding values.

• Hash map uses a hash function to calculate the index of the key in the underlying array.

• Collisions can occur when multiple keys hash to the same index, which is resolved using techniques like chaining or open addressing.

• Retrieving a value from a hash map is done by hashing the key to find its index and then accessing the value stored at that index.

JOIN in SQL is used to combine rows from two or more tables based on a related column between them.

• JOIN is used to retrieve data from multiple tables based on a related column

• Types of JOIN include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column

A thread is invoked by calling its start() method.

• A thread is invoked by calling the start() method on an instance of the Thread class.

• The start() method creates a new thread and invokes the run() method of the thread.

• Threads can also be invoked by implementing the Runnable interface and passing it to a Thread constructor.