谨慎重载clone方法

- public class Car implements Cloneable {
- private Object containedObj1 = new Object();
- private Object containedObj2 = new Object();
- public Object getObj1() {
- return containedObj1;
- }
- public Object getObj2() {
- return containedObj2;
- }
- @Override
- protected Object clone() throws CloneNotSupportedException {
- return (Car) super.clone();
- }
- public Car() {
- }
- public static void main(String[] args) {
- try {
- Car obj1 = new Car();
- Car obj2 = (Car) obj1.clone();
- System.out.println("obj1 and obj2 are same:" + (obj1 == obj2));
- System.out.println("obj1.containedObj1 and obj2.containedObj1 are same:" + (obj1.getObj1() == obj2.getObj1()));
- System.out.println("obj1.containedObj2 and obj2.containedObj2 are same:" + (obj1.getObj2() == obj2.getObj2()));
- System.out.println("obj1.str and obj2.str are same:" +(obj2.getString() == obj1.getString()));
- System.out.println("obj1.data:" + obj1.getData()+"; obj2.data:" + obj2.getData());
- System.out.println("obj1.dataf:" + obj1.getDataf()+"; obj2.dataf:" + obj2.getDataf());
- } catch (CloneNotSupportedException e) {
- e.printStackTrace();
- }
- }
- }

- public class Car2 {
- private Object containedObj1 = new Object();
- private Object containedObj2 = new Object();
- private String str = "oneStr";
- private int data = 1024;
- private float dataf = 1024.1024f;
- public Car2() {
- }
- public Car2(Car2 car) {
- this.str = new String(car.getString().toString());
- this.data = car.getData();
- this.dataf = car.getDataf();
- }
- private String getString() {
- return str;
- }
- public int getData() {
- return data;
- }
- public float getDataf() {
- return dataf;
- }
- public Object getObj1() {
- return containedObj1;
- }
- public Object getObj2() {
- return containedObj2;
- }
- public static void main(String[] args) {
- Car2 obj1 = new Car2();
- Car2 obj2 = new Car2(obj1);
- System.out.println("obj1 and obj2 are same:" + (obj1 == obj2));
- System.out.println("obj1.containedObj1 and obj2.containedObj1 are same:" + (obj1.getObj1() == obj2.getObj1()));
- System.out.println("obj1.containedObj2 and obj2.containedObj2 are same:" + (obj1.getObj2() == obj2.getObj2()));
- System.out.println("obj1.str and obj2.str are same:" +(obj2.getString() == obj1.getString()));
- System.out.println("obj1.data:" + obj1.getData()+"; obj2.data:" + obj2.getData());
- System.out.println("obj1.dataf:" + obj1.getDataf()+"; obj2.dataf:" + obj2.getDataf());
- }
- }
- @Override
- protected Object clone() throws CloneNotSupportedException {
- Body newBody = (Body) super.clone();
- newBody.head = (Head) head.clone();
- return newBody;
- }
- public class Body implements Cloneable {
- public Head head;
- public Body() {
- }
- public Body(Head head) {
- this.head = head;
- }
- @Override
- protected Object clone() throws CloneNotSupportedException {
- Body newBody = (Body) super.clone();
- newBody.head = (Head) head.clone();
- return newBody;
- }
- public static void main(String[] args) throws CloneNotSupportedException {
- Body body = new Body(new Head());
- Body body1 = (Body) body.clone();
- System.out.println("body == body1 : " + (body == body1));
- System.out.println("body.head == body1.head : " + (body.head == body1.head));
- }
- }
- class Head implements Cloneable/* implements Cloneable */ {
- public Face face;
- public Head() {
- }
- public Head(Face face) {
- this.face = face;
- }
- @Override
- protected Object clone() throws CloneNotSupportedException {
- return super.clone();
- }
- }
- class Face {
- }
- public class Body2 implements Cloneable {
- public Head head;
- public Body2() {
- }
- public Body2(Head head) {
- this.head = head;
- }
- @Override
- protected Object clone() throws CloneNotSupportedException {
- Body2 newBody = (Body2) super.clone();
- newBody.head = (Head) head.clone();
- return newBody;
- }
- public static void main(String[] args) throws CloneNotSupportedException {
- Body2 body = new Body2(new Head(new Face()));
- Body2 body1 = (Body2) body.clone();
- System.out.println("body == body1 : " + (body == body1));
- System.out.println("body.head == body1.head : " + (body.head == body1.head));
- System.out.println("body.head.face == body1.head.face : " + (body.head.face == body1.head.face));
- }
- }
- class Head implements Cloneable/* implements Cloneable */ {
- public Face face;
- public Head() {
- }
- public Head(Face face) {
- this.face = face;
- }
- @Override
- protected Object clone() throws CloneNotSupportedException {
- return super.clone();
- }
- }
- class Face {
- }
- public final class Galaxy {
- /**
- * Regular constructor.
- */
- public Galaxy(double aMass, String aName) {
- fMass = aMass;
- fName = aName;
- }
- /**
- * Copy constructor.
- */
- public Galaxy(Galaxy aGalaxy) {
- this(aGalaxy.getMass(), aGalaxy.getName());
- //no defensive copies are created here, since
- //there are no mutable object fields (String is immutable)
- }
- /**
- * Alternative style for a copy constructor, using a static newInstance
- * method.
- */
- public static Galaxy newInstance(Galaxy aGalaxy) {
- return new Galaxy(aGalaxy.getMass(), aGalaxy.getName());
- }
- public double getMass() {
- return fMass;
- }
- /**
- * This is the only method which changes the state of a Galaxy
- * object. If this method were removed, then a copy constructor
- * would not be provided either, since immutable objects do not
- * need a copy constructor.
- */
- public void setMass(double aMass){
- fMass = aMass;
- }
- public String getName() {
- return fName;
- }
- // PRIVATE
- private double fMass;
- private final String fName;
- /** Test harness. */
- public static void main (String... aArguments){
- Galaxy m101 = new Galaxy(15.0, "M101");
- Galaxy m101CopyOne = new Galaxy(m101);
- m101CopyOne.setMass(25.0);
- System.out.println("M101 mass: " + m101.getMass());
- System.out.println("M101Copy mass: " + m101CopyOne.getMass());
- Galaxy m101CopyTwo = Galaxy.newInstance(m101);
- m101CopyTwo.setMass(35.0);
- System.out.println("M101 mass: " + m101.getMass());
- System.out.println("M101CopyTwo mass: " + m101CopyTwo.getMass());
- }
- }
- 输出结果:
- M101 mass: 15.0
- M101Copy mass: 25.0
- M101 mass: 15.0
- M101CopyTwo mass: 35.0
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