Sample Flashcards
What is an Object?
refers to a particular instance of a class where the object can be a combination of variables, functions, and data structures.
What is a Class?
an extensible program-code-template for creating objects, providing initial values for state (member variables) and implementations of behavior (member functions or methods).
What is concurrency?
When two processes are assigned to different cores on a machine by the kernel, and both cores execute the process instructions at the same time.
What is a deadlock?
A deadlock occurs when two or more tasks permanently block each other by each task having a lock on a resource which the other tasks are trying to lock.
What is the difference between HashMap and TreeMap?
HashMap is implemented as a hash table, and there is no ordering on keys or values. TreeMap is implemented based on red-black tree structure, and it is ordered by the key.
The types of joins in SQL?
JOIN or INNER JOIN
2. OUTER JOIN
2. 1 LEFT OUTER JOIN or LEFT JOIN 2. 2 RIGHT OUTER JOIN or RIGHT JOIN 2. 3 FULL OUTER JOIN or FULL JOIN
- NATURAL JOIN
- CROSS JOIN
- SELF JOIN
What is normalization in SQL?
a systematic approach of decomposing tables to eliminate data redundancy and undesirable characteristics
How do you handle exceptions in JAVA? What are the different types of exceptions?
1) Checked exceptions
2) Unchecked exceptions
What is the difference between overloading and overriding?
Method overloading deals with the notion of having two or more methods in the same class with the same name but different arguments. Method overriding means having two methods with the same arguments, but different implementations.
What is inheritance?
lets you create classes that are derived from other classes.
What is a method?
A method is a set of code which is referred to by name and can be called (invoked) at any point in a program simply by utilizing the method’s name.
What is an array?
An array is a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created.
What is collection?
a framework that provides an architecture to store and manipulate the group of objects.
What is the relationship between a class and an object?
Class is a definition, while object is a instance of the class created. Class is a blue print while objects are actual objects existing in real world.
what is a full outer left joint
keyword return all records when there is a match in either left (table1) or right (table2) table records.
What is an interface?
An interface is a reference type in Java. It is similar to class. It is a collection of abstract methods
What is an abstract class?
Abstract classes are classes that contain one or more abstract methods. An abstract method is a method that is declared
What is Primary Key.
a key in a relational database that is unique for each record.
What is the difference between DELETE and TRUNCATE? What is a trigger?
No DML triggers will be fired. The operation cannot be rolled back. DROP and TRUNCATE are DDL commands, whereas DELETE is a DML command. Therefore DELETE operations can be rolled back (undone), while DROP and TRUNCATE operations cannot be rolled back.
what do variables do
a value that can change, depending on conditions or on information passed to the program.
