Constructor-
Definition-
Constructor is used to construct the objects.
-It initialize default or given values to object.
Syntax-
modifiers ClassName(parameters) { //Constructor body }
Rules of creation-
1- Constructor Name should be same as class name.
Rules of implementation-
1- constructor always should be followed by new keyword.
Types of constructor-
1- Non Parameterized constructor
2– Parameterized constructor
1- Non Parameterized
(i)Default constructor-
Only when no constructor is created in class, compiler adds default constructor.
Syntax- created by compiler in compiled code- constructorName(){ }
(ii) Manual Constructor-
Constructor created with no parameters.
It can have statements in constructor body.
Syntax - modifiers constructorName(){ Statements }
2- Parameterized Constructor-
Constructor created with parameters.
It also can have statements in constructor body.
Syntax- modifiers constructotName(parameters) { Statements }
Methods-
method is a set of statements to perform operations
Syntax –
Modifiers returnType methodName(parameters) { //statements }
Note- ReturnType= datatypes + void
code samples are here
1-Program to use default constructor(automatic creation)-
package constructors3; public class Const1 { public static void main(String[] args) { Const1 c1 = new Const1(); } }
2-Program to create manual constructor which prints “a” and then use this manual constructor –
package constructors3; public class Const2 { public Const2() { System.out.println("a"); } public static void main(String[] args) { Const2 c1 = new Const2(); } }
3-Program to create parameterized constructor which takes String s as parameter and then use it by giving “Got it” as argument –
package constructors3; public class Const3 { public Const3(String s) { System.out.println(s); } public static void main(String[] args) { Const3 name = new Const3("Got it"); } }
4-Program to create more than 1 constructor with different parameters then use all constructors by giving arguments.
package constructors3; public class Const4 { public Const4(int i,String a) { System.out.println(i+a); } public Const4(String a,int i) { System.out.println(a+i); } public Const4(double h,char o) { System.out.println(h+" "+o); } public static void main(String[] args) { Const4 c = new Const4(6, "deep"); Const4 c1 = new Const4(65.45d, 'p'); Const4 c2 = new Const4("kaushik",10); } }
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