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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