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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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