Java Constructors - W3Schools

A constructor in Java is a special method that is used to initialize objects. The constructor is called when an object of a class is created. 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Theconstructoriscalledwhenanobjectofaclassiscreated.Itcanbeusedto setinitialvaluesforobjectattributes: Example Createaconstructor: //CreateaMainclass publicclassMain{  intx; //Createaclassattribute  //CreateaclassconstructorfortheMainclass  publicMain(){    x=5; //Settheinitialvaluefortheclassattributex  }  publicstaticvoidmain(String[]args){    MainmyObj=newMain();//CreateanobjectofclassMain(Thiswillcalltheconstructor)    System.out.println(myObj.x);//Printthevalueofx  } } //Outputs5 TryitYourself» Notethattheconstructornamemustmatchtheclassname,anditcannothavea returntype(likevoid). Alsonotethattheconstructoriscalledwhentheobjectiscreated. Allclasseshaveconstructorsbydefault:ifyoudonotcreateaclassconstructor yourself,Javacreatesoneforyou.However,thenyouarenotabletosetinitialvaluesforobjectattributes. ConstructorParameters Constructorscanalsotakeparameters,whichisusedtoinitialize attributes. Thefollowingexampleaddsanintyparameter totheconstructor. Insidetheconstructorwesetxtoy(x=y).Whenwecall theconstructor,wepassaparametertotheconstructor(5),whichwillsetthevalueof xto5: Example publicclassMain{  intx;  publicMain(inty){    x=y;  }  publicstaticvoidmain(String[]args){    MainmyObj=newMain(5);    System.out.println(myObj.x);  } } //Outputs5 TryitYourself» Youcanhaveasmanyparametersasyouwant: Example publicclassMain{  intmodelYear;  StringmodelName;  publicMain(intyear,Stringname){    modelYear=year;    modelName=name;  }  publicstaticvoidmain(String[]args){    MainmyCar=newMain(1969,"Mustang");    System.out.println(myCar.modelYear+""+myCar.modelName);  } } //Outputs1969Mustang TryitYourself» ❮Previous Next❯ NEW WejustlaunchedW3Schoolsvideos Explorenow COLORPICKER Getcertifiedbycompletingacoursetoday! w3schoolsCERTIFIED.2022 Getstarted CODEGAME PlayGame