Learn Java language fundamentals with Unit nexus

Java Language Fundamentals / 1 of 28

Java Language Fundamentals

Session 2


Objectives

Interpret the Java program Understand the basics of the Java language Identify data types


Java Program Structure

Environment Information Class Declaration Tokens:

Identifiers Keywords / Reserve words Separators Literals Operators


Sample Java program


Compiling and executing the sample program


Passing Command Line Arguments (1)


Passing Command Line Arguments (2)


Basics of the Java Language

Classes & Methods

Data types

Variables

Operators

Control structures


Classes in Java

Class declaration Syntax

class Classname {

var_datatype variablename;:

met_datatype methodname(parameter_list):

}


Sample class


Nested Classes

Defining one class within another is called ‘Nesting’

Types: Static Non-static


Data Types

byte char boolean short int long float double

Array

Class

Interface


Type Casting

One data type is converted into another data type

Example float c = 34.89675f;

int b = (int)c + 10;


Variables

Three components of a variable declaration: Data type Name Initial value to be assigned (optional)

Syntaxdatatype identifier [=value][, identifier[=value]...];


Java Reserve words


Array Declarations

Three ways for Array Declaration: datatype identifier [ ];

datatype identifier [ ] = new datatype[size];

datatype identifier [ ]= {value1,value2,….valueN};


Methods in Classes

A method is defined as the actual implementation of an operation on an object

Syntax access_specifier modifier datatype method_name(parameter_list)

{

//body of method

}


Sample usage of Method


Access specifiers for Methods


Method Modifiers static

abstract

final

native

synchronized

volatile


Methods Overloading

Overloaded Methods: Are in the same class Have the same name Have different parameter lists

Overloaded methods are a form of compile time polymorphism


Methods Overriding

Overridden Methods: Are in the superclass as well as the subclass Are redefined in the subclass

Overridden methods are a form of runtime polymorphism


Class Constructors

Special method used to initialize member variables of the class

Same name as the Class name and does not have a return type

Called when an object is created Types:

Explicit constructors Implicit constructors


Derived class constructors

Has the same name as the subclass

Statement that calls the constructor of the superclass should be the first statement in the constructor of a subclass


Operators

Java Provides following categories of Operators: Arithmetic Operators Bitwise Operators Relational Operators Logical Operators Conditional Operators Assignment Operators


Operator Precedence


Escape Sequence


Control Flow

Decision – making if-else statement Switch-else statement

Loops while loop do-while loop for loop

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