Constructor in java

Constructor in java

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  Presented by, Siva ShankariRajan, CPSV
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  CONTENTS What is Constructor Typesof Constructor Constructor overloading 1 2 3 4 Passing initial values as arguments
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  1 Java Constructor A constructorin Java is a special method that is used to initialize objects. The constructor is called when an object of a class is created. It can be used to set initial values for object attributes
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  2 Rules for JavaConstructor The constructor name must match the name of the class The default constructor is ALWAYS as no-arg constructor Constructors can use any access modifier, including private Constructors must not have a return type.
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  3 Difference Between Constructorand Method Constructor are used to initialize the state of object Constructor must not have return type Constructor compil er provide default constructor . Method is expose the behaviour of object. Method must have return type. Method compiler does't provide. 1 2 3 1 2 3
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  4 Types of JavaConstructor Default constructor Parameterized constructor Copy constructor
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  5 01 02 A constructor that haveno parameter is known as default constructor. Syntax of default constructor: <class_name>(){} Default Constructor Class Measuring { Private double Metre; Private double kilometer; Private double centimeter; Private double Millimeter; Measuring() { Metre=120; kilometer=10.0; centimeter=12.0; Millimeter=5.0; } Void display() { System.out.println(“kilometer=“+kilometer); } } Output: Kilometer=10.0
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  6 01 02 A constructor thathave parameters is known as parameterized constructor. Parameterized constructor is used to provide different values to the distinct objects Parameterize dconstructor Class Rectangle { int length; int breadth; Rectangle(int len, int bre) { length=len; breadth=bre; } } Class demo { Public static void main(String args[]) { Rectangle r1= new Rectangle(20,10); System.out.println(“length of rectangle=“ r1.length); System.out.println(“breadth of rectangle=“ r1.breadth); }}
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  7 01 02 We can createthe object with any initial value to extract values in the parameterized constructor Parameterized constructor can pass a value as: 1. An implicit call 2. An explicit call Passing initial values As arguments Implicit call constructor: It retrieves the parameterized constructor even if it is not declared in the main(). We can create the object with any initial value to extract values in the parameterized constructor Explicit call constructor: It helps in creating a temporary instance. A temporary instance remains in the memory as long as it is being used in an expression.
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  8 01 02 It is usedto create a temporary object of a class object. A copy constructor takes only one argument, which is of the type as the class. Copy constructor Class Rectangle { int length; int breadth; Rectangle(int len, int bre) { length=len; breadth=bre; } Rectangle(Rectangle obj) { System.out.println(“copy constructor invoked”); length=obj.len; breadth=obj.bre; } int area() { return(length*breadth); }
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  9 01 02 It is usedto create a temporary object of a class object. A copy constructor takes only one argument, which is of the type as the class. Copy constructor Class demo { Public static void main(String args[]) { Rectangle r1= new Rectangle(20,10); Rectangle r2=new Rectangle(r1); System.out.println(“area of 1st rectangle=“ r1.area()); System.out.println(“area of 2nd rectangle=“ r2.area()); }}
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  10 01 02 A constructor maybe overloaded, so a single class may have more than one constructor, all of which have the same name but different argument lists. Constructor overloading Class overloading { int x, float y; Overloading() {x=0;y=0.0;} Overloading(int a) {x=a; y=0;} Overloading(int a, float b) {x=a; y=b;} Public static void main(String args[]) { Overloading ov1=new overloading(); Overloading ov2=new overloading(40); Overloading ov3=new overloading(10,4.5); } }