- What is JAVA?
Java is a free open source, object oriented programming language. It is platform independent, supports multithreading and enables high performance.
- What is JDK?
JDK stands for Java Development Kit. JDK is required to compile and package java programs. It consists of JRE.
- What is JRE?
JRE stands for Java Runtime Environment. It provides required libraries and JVM to run java programs.
- What is JVM?
JVM stands for Java Virtual Machine. It is used to execute java programs.
- What is JIT compiler?
JIT stands for Just In Time. JIT compiler is used to compile byte code into executable code.
- What are the different primitive data types in Java ?
Following are the primitive data types -
- char
- byte
- short
- int
- float
- double
- long
- boolean
- What are wrapper classes?
For every primitive data type in java we have a corresponding class in java to convert it into an object, these classes are known as wrapper classes.
Following are the wrapper classes -
- Character
- Byte
- Short
- Integer
- Float
- Double
- Long
- Boolean
- What is autoboxing and unboxing?
Autoboxing is a way of converting primitive data types to objects and Unboxing is a way to convert objects into primitive data types.
- What are nested classes?
A class declared within a class is called nested class.
- What are the different types of nested class?
- Static Nested Class - It is a nested class declared with static keyword and can be instantiated without creating the object of outer class.
- Non Static Nested Class - It is a nested class declared without static keyword and is also known as Inner Class.
- What is a constructor?
A constructor has the name as that of the class, it is a method without any return type, used for creating the object of a class.
- What are the types of constructors?
Constructors are of two types -
- Default - Constructor without any parameters.
- Parameterised - Constructor with parameters.
- What is static keyword?
Static variables and methods are created to be used by multiple objects. They can be called without creating the object of a class.
Static methods cannot be overridden.
Static block is used to execute a piece of code when the application starts.
- What is final keyword?
- Class - If a class is declared as final, then it cannot be extended. Inheritance cannot be achieved if a class is declared as final.
- Method - If a method is declared as final, it cannot be overridden. Polymorphism cannot be achieved if a method is declared as final.
- Variable - If a variable is declared as final, its value cannot be changed. It becomes a Constant.
- What is this() keyword?
this() is used to call one constructor from another within the same class.
- What is super keyword?
super() is used by sub class to access the variables and methods of super class.
- What is Serialization?
Serialization is a way to save the state of the object when passing it over a network stream by converting it into bytes.
- What is transient?
