J2SE Object-oriented _ overloaded _this_static_package_import_ inheritance _ access control

Overloading of methods

Constructing method Overloads

creation and use of objects

classPoint {Private Doublex; Private Doubley; Point (DoubleX1,Doubley1) {x=X1; Y=Y1; }     Public DoubleGetX () {returnx;}  Public DoubleGetY () {returny;}  Public voidSetX (Doublei) {x =i;}  Public voidSety (Doublei) {y =i;}}classCircle {PrivatePoint o; Private Doubleradius; Circle (point P,Doubler) {o=p; Radius=R; } Circle (Doubler) {o=NewPoint (0.0, 0.0); Radius=R; }        Booleancontains (point p) {Doublex = P.getx ()-O.getx (); Doubley = p.gety ()-o.gety (); if(x*x + y*y > Radius * radius)return false; Else return true; }             Public voidSetO (DoubleXDoubley) {o.setx (x);    O.sety (y); }     PublicPoint Geto () {returno;}  Public DoubleGetradius () {returnradius;}  Public voidSetradius (Doubler) {radius =R;}  Public DoubleArea () {return3.14 * RADIUS *radius; }} Public classtestcircle { Public Static voidMain (String args[]) {Circle C1=NewCircle (NewPoint (1.0,2.0), 2.0); Circle C2=NewCircle (5.0); System.out.println ("C1: (" +c1.geto (). GetX () + "," +c1.geto (). GetY () + ")," +C1.getradius ()); System.out.println ("C2: (" +C2.geto (). GetX ()+ "," +c2.geto (). GetY () + ")," +C2.getradius ()); System.out.println ("C1 area =" +C1.area ()); System.out.println ("C1 area =" +C2.area ()); C1.seto (5,6); C2.setradius (9.0); System.out.println ("C1: (" +c1.geto (). GetX () + "," +c1.geto (). GetY () + ")," +C1.getradius ()); System.out.println ("C2: (" +c2.geto (). GetX () + "," +c2.geto (). GetY () + ")," +C2.getradius ()); System.out.println ("C1 area =" +C1.area ()); System.out.println ("C1 area =" +C2.area ()); Point P1=NewPoint (5.2, 6.3);        System.out.println (C1.contains (p1)); System.out.println (C1.contains (NewPoint (10.0,9.0))); }}

Testcircle.javaThis keyword

Static keyword

 Public classCat {Private Static intSid = 0; PrivateString name; intID; Cat (String name) { This. Name =name; ID= sid++; }     Public voidinfo () {System.out.println ("My name is" +name+ "No." +ID); }     Public Static voidMain (String arg[]) {Cat.sid= 100; Cat Mimi=NewCat ("Mimi"); Mimi.sid= 2000; Cat Pipi=NewCat ("Pipi");         Mimi.info ();    Pipi.info (); }}

Cat.javaPackage and Import statements

Introduction to the main packages in J2SDK

class inheritance and permission control

classPerson {PrivateString name; Private intAge ;  Public voidsetName (String name) { This. name=name; }     Public voidSetage (intAge ) {         This. age=Age ; }     PublicString GetName () {returnname; }     Public intGetage () {returnAge ; }}classStudentextendsPerson {PrivateString School;  PublicString Getschool () {returnSchool; }     Public voidSetschool (String school) { This. School =School; } } Public classTest { Public Static voidMain (String arg[]) {Student Student=NewStudent (); Student.setname ("John"); Student.setage (18); Student.setschool ("SCH");        System.out.println (Student.getname ());        System.out.println (Student.getage ());    System.out.println (Student.getschool ()); }}

Testperson.javaAccess Control

 Public classtestaccess {}classT {Private inti = 0; intj = 0; protected intK = 0;  Public intm = 0;  Public voidm () {i= 9; }}classTT { Public voidm () {T T=NewT ();    System.out.println (T.J); }}

Testaccess.java

J2SE Object-oriented _ overloaded _this_static_package_import_ inheritance _ access control