Learn Java language fundamentals with Unit nexus

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Java Language Fundamentals

Session 2

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Objectives

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

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Java Program Structure

Environment Information Class Declaration Tokens:

Identifiers Keywords / Reserve words Separators Literals Operators

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Sample Java program

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Compiling and executing the sample program

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Passing Command Line Arguments (1)

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Passing Command Line Arguments (2)

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Basics of the Java Language

Classes & Methods

Data types

Variables

Operators

Control structures

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Classes in Java

Class declaration Syntax

class Classname {

var_datatype variablename;:

 met_datatype methodname(parameter_list):

}

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Sample class

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Nested Classes

Defining one class within another is called ‘Nesting’

Types: Static Non-static

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Data Types

byte char boolean short int long float double

Array

Class

Interface

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Type Casting

One data type is converted into another data type

Example float c = 34.89675f;

int b = (int)c + 10;

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Variables

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

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

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Java Reserve words

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Array Declarations

Three ways for Array Declaration: datatype identifier [ ];

datatype identifier [ ] = new datatype[size];

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

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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

}

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Sample usage of Method

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Access specifiers for Methods

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Method Modifiers static

abstract

final

native

synchronized

volatile

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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

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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

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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

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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

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Operators

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

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Operator Precedence

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Escape Sequence

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Control Flow

Decision – making if-else statement Switch-else statement

Loops while loop do-while loop for loop

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