Java SE
Explain Bean in Spring
Beans are objects that form the backbone of a Spring application
What is an anonymous class?
Class defined without a name in a single line of code using new keyword
What is an abstract class?
Class marked with abstract keyword that can have any number of abstract or non abstract methods
Explain Unchecked Exceptions
Classes that extend RuntimeException and They're not checked during compilation time
Explain Checked Exceptions
Classes that extend Throwable class (except Runtime and Error) and they're checked at compilation time
What is a package?
Collection of related classes and interfaces
Explain Hibernate architecture
Configuration Session factory Session Transaction Query Criteria
Main concepts of OOPs in java?
Inheritance Encapsulation Abstraction Polymorphism
State two differences between an inner class and a subclass
Inner classes are in the same file / Subclasses can be in another file Inner classes get the methods they want / Subclasses have methods of their parent class
What is an object in java?
Is a real world entity that has a state an behavior
What is an interface?
Is an improved abstract class that contains a set of abstract methods
What are the functions of JVM ?
JVM provides a runtime environment for Java Byte Codes to be Executed
What do JDK, JRE and JVM stand for?
JVM stands for Java Virtual Machine JRE stands for Java Runtime Environment JDK stands for Java Develpment Kit
What is a JVM?
Java Virtual Machine, which is a runtime environment for compiled Java class files
Classes and Interfaces available in collections
List Set Map Sorted Set Sorted Map Queue ArrayList Vector LinkedList HashSet LinkedHashSet TreeSet HashMap HashTable TreeMap LinkedHashMap
Explain lists available in the Collection
List allows duplicates and its elements are ordered by index position ArrayList Vector (Synchronized) LinkedList (slower than ArrayList)
Explain Map and their types in Collection
Map cares about unique identifier key-value HashMap HashTable TreeMap
What is encapsulation?
Mechanism of wrapping up the data and code together as a single unit
What is abstraction?
Methodology of hiding the implementation details from the user and only providing the functionality to the users
What is Multi-threading?
Multiple threads executed simultaneously
Can a Dead thread be started again?
No
Does java use pointers?
No, Java doesn't use pointers, instead of that, references are used as they are safer
In Spring Scope, explain Singleton
Only one instance of the bean will be created for each container. This is the default scope for the spring beans.
What is the difference between Overloading and Overriding?
Overloading has a different method signature
Can you override a private or static method in java?
Private, no because only elements within the same class have access static, no because instead of inheritance you're hiding the superclass method
What is mean by exception?
Problem that can occur during an execution
What is inheritance?
Process where one class acquires the properties of another
What is Multi-Threading?
Programming concept used to run multiple tasks in a concurrent manner within a single program
What is Object Oriented Programming (OOP)?
Programming model where the programs are organized around objects rather than logic and functions
How do you connect to a database in java?
Registering the driver class Creating connection Creating statement Executing queries Closing connection
Explain Set and their types in Collection
Set don't allow duplications HashSet LinkedHashSet TreeSet
List the different scopes of spring bean
Singleton Prototype Request Session Global-Session
What is a singleton class in Java and how can we make a class singleton?
Singleton class is a class whose only one instance can be crated at any given time, in one JVM A class can be made singleton by making its constructor private
What are access modifiers in java?
Special keywords which are used to restrict the access of class, constructor, variables, etc.
Name the different modules of the Spring framework
Spring Context - dependency injection Spring AOP - oriented programming Spring DAO - database operations using DAO pattern Spring JDBC Spring ORM Spring Web Module Spring MVC
Difference between stack and queue?
Stack is based on LIFO (Last In First Out) and queue is based on FIFO (First In First Out)
Difference between String, StringBuilder and StringBuffer
String is an object immutable StringBuilder and StringBuffer are mutable but StringBuffer is synchronized so is slower than StringBuilder
What is a variable?
attribute that defines the state of a class
Difference between final, finally and finalize
final is an optional specifier that means non-access finally is a code block executed after try/catch blocks finalize works with the Garbage Collector
Link
https://www.edureka.co/blog/interview-questions/java-interview-questions/#java-platform-independent
Most important feature of java:
is a platform independent language
What's the Base class of all exception classes?
java.lang.Throwable
What are the life-cycle of methods for a jsp?
jspInit - invoked only once, same as init() of servlet _jspService - invoked at each request jspDestroy - invoked only once, same as detroy() of servlet
What is polymorphism?
property of an object to take on many different forms
Difference between start() and run() in thread class?
start() creates new thread and the code inside run() is executed in the new thread
What's the difference between this() and super() in java?
this() is used to call a constructor of the same class super() is used to call a constructor of the parent class
How you can handle java exceptions?
try catch finally throw throws
What are constructors in java?
Block of code used to initialize an object
What are the types of Exceptions?
Checked Exceptions Unchecked Exceptions
Define CLASS in Java
Container of all java codes, includes variables and methods
What is a method?
Contains a set of statements or instructions to satisfy a particular requirement
What is meant by Serialization?
Converting a file into a byte stream
What are the different tags provided in JSTL?
Core tags SQL Tags XML Tags Internationalization tags Functions tags
What are the types of constructor?
Default constructor (no parameters) Parameterized constructor (has parameters)
What is autowiring in spring?
Enables the programmer to inject the bean automatically
What's the difference between equals and ==?
Equals is used to compare two objects == is used to compare primitives and objects
Difference between Error and Exception
Error is an irrecoverable condition during runtime Exceptions are conditions that occur because of bad input, human error, etc. And is possible to recover from it
How do you make a thread in java?
Exted Thread class Implement runnable interface
What are Collections in Java?
Framework used for search, sort, manipulate, insert and delete a set of objects
What is java string pool?
Heap memory space that collects a set of string literals
What is java?
High-level programming language and platform independent
What are the functions of JRE?
Includes sets of files required by JVM during runtime
In Srpint, explain the role of ContextLoaderListener
Listener to start up and shut down the WebApplicationContext in Spring root. An important function is tying up the lifecycle of Application Context to the lifecycle of the ServletContext and automating the creation of ApplicationContext
What is synchronization?
Makes only one thread to access a block of code at a time
What is the disadvantage of Synchronization?
Makes slow performance because threads have to wait until the code is enable
What are the features in Java?
OOPs concepts: *Object O
What is Hibernate Framework?
Object-relational mapping (ORM) for mapping application domain objects to the relational databse tables and vice versa
Explain garbage collection in java
When an object is no longer in use or referenced, garbage collection is called and the object is destroyed
What are wrapper classes in java?
Wrapper classes convert the Java primitives into objects. Are wrapper classes because they wrap the primitive data type
Which are the access modifiers?
private default package private protected public
In Spring Scope, explain Global-Session
Used to create global session beans for Portlet applications
How to stop a thread in java?
Using the following methods: sleeping waiting blocked
What are some of the important Spring annotations which you have used?
@Controller @RequestMapping @ResponseBody @PathVariable @Autowired
List some of the important annotations in annotation-based spring configuration
@Required @Autowired @Qualifier @Resource @PostConstruct @PreDestroy
Difference between ArrayList and Vector in java?
*ArrayList is not sychronized (Vector is) *ArrayList is faster as it's not synchornized (Vector slower) *ArrayList doesn't define the increment size (Vector does) *ArrayList can only use Iterator (Vector can use Enumeration and Iterator)
Difference between abstract class and interface?
*Type of methods *Type of variables *Method implementation *Inheritance vs abstraction *Multiple implementation *Abstract keyword
What is spring?
A lightweight, integrated framework that can be used for developing enterprise applications
In Spring Scope, explain Session
A new bean will be created for each HTTP session by the container
In Spring Scope, explain Request
A new instance of the bean will be created for each HTTP request
In Spring Scope, explain Protptype
A new instance will be created every time the bean is requested
What is FINAL keyword in java?
A non-access specifier that can be used in: variable, method, class
What is a thread?
The flow of an execution
In Spring, explain the role of DispatcherServlet
The front controller in Spring MVC application, loads the spring bean configuration file and initializes all the beans that have been configured. Also scans the packages to configure any bean annotated with @Component, @Controller, @Repository or @Service
