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本篇內(nèi)容介紹了“Java中的clone()和Cloneable接口使用方法是什么”的有關(guān)知識，在實(shí)際案例的操作過程中，不少人都會遇到這樣的困境，接下來就讓小編帶領(lǐng)大家學(xué)習(xí)一下如何處理這些情況吧！希望大家仔細(xì)閱讀，能夠?qū)W有所成！
clone顧名思義就是克隆，即，復(fù)制一個(gè)相等的對象，但是不同的引用地址。
我們知道拿到一個(gè)對象的地址，只要提供相應(yīng)的方法就可以修改這個(gè)對象，但是如果我們想要得到這個(gè)對象去修改它，又想保留這個(gè)對象原來的屬性，這是就可以使用clone()，它會復(fù)制一個(gè)內(nèi)容相同的對象而具有不同內(nèi)存地址。
Cloneable接口，就是我們要使用clone()必須實(shí)現(xiàn)的接口，不然會拋出異常。
public class Bean implements Cloneable {
private String a;
public Bean(String a) {
this.a = a;
}
public String getA() {
return a;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
@Override
public boolean equals(Object o) {
if(o instanceof Bean){
Bean bean = (Bean) o;
return bean.getA().equals(a);
}
return false;
}
}在Cloneable 接口中并沒有給我們定義任何方法
這里需要重寫clone()方法
protected native Object clone() throws CloneNotSupportedException;
protected Object clone() throws CloneNotSupportedException {
if (!(this instanceof Cloneable)) {
throw new CloneNotSupportedException("Class " + getClass().getName() +
" doesn't implement Cloneable");
}
return internalClone();
}它是Object類里面的native方法，它是protected的，根據(jù)需要可以寫為public，可以看到如果不實(shí)現(xiàn)Cloneable接口將會拋出CloneNotSupportedException 異常。
測試一下
try {
Bean a = new Bean("lzy");
Bean b = a;
Bean c = (Bean) a.clone();
Log.i(TAG, "onCreate: " + (a == b)); //true
Log.i(TAG, "onCreate: " + (a.equals(b))); //true
Log.i(TAG, "onCreate: " + (a == c)); //false
Log.i(TAG, "onCreate: " + (a.equals(c))); //true
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}可以看到克隆出來的類的地址是不同的，而內(nèi)容是相同的。
下面修改一下，在Bean加一個(gè)成員變量ChildBean
public class ChildBean implements Cloneable {
private String c;
public String getC() {
return c;
}
public ChildBean(String c) {
this.c = c;
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
@Override
public boolean equals(Object o) {
if (o instanceof ChildBean) {
ChildBean bean = (ChildBean) o;
return bean.getC().equals(c);
}
return false;
}
}public class Bean implements Cloneable {
private String a;
private ChildBean childBean;
public Bean(String a, ChildBean childBean) {
this.a = a;
this.childBean = childBean;
}
public String getA() {
return a;
}
public ChildBean getChildBean() {
return childBean;
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
@Override
public boolean equals(Object o) {
if (o instanceof Bean) {
Bean bean = (Bean) o;
return bean.getA().equals(a);
}
return false;
}
}Bean a = new Bean("lzy", new ChildBean("child"));
Bean b = a;
Bean c = (Bean) a.clone();
Log.i(TAG, "onCreate: " + (a.getChildBean() == b.getChildBean())); //true
Log.i(TAG, "onCreate: " + (a.getChildBean().equals(b.getChildBean()))); //true
Log.i(TAG, "onCreate: " + (a.getChildBean() == c.getChildBean())); //true
Log.i(TAG, "onCreate: " + (a.getChildBean().equals(c.getChildBean()))); //true測試發(fā)現(xiàn)有一個(gè)結(jié)果不是我們所預(yù)期的，這意味著并沒有真正克隆ChildBean，只是克隆的它的內(nèi)存地址，導(dǎo)致兩個(gè)具有相同的內(nèi)存地址，這也就是淺克隆，此時(shí)我們需要的是深克隆，需要按照下面方法修改，重寫clone()方法
@Override
public Object clone() throws CloneNotSupportedException {
Bean bean = (Bean) super.clone();
bean.childBean = (ChildBean) bean.childBean.clone();
return bean;
}但是這樣做如果有很多層的類，那每一層都需要去重寫，顯得很麻煩。所以我們可以用下面的工具類來實(shí)現(xiàn)
public class BeanUtil {
public static <T> T cloneTo(T src) throws RuntimeException {
ByteArrayOutputStream memoryBuffer = new ByteArrayOutputStream();
ObjectOutputStream out = null;
ObjectInputStream in = null;
T dist = null;
try {
out = new ObjectOutputStream(memoryBuffer);
out.writeObject(src);
out.flush();
in = new ObjectInputStream(new ByteArrayInputStream(memoryBuffer.toByteArray()));
dist = (T) in.readObject();
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
if (out != null)
try {
out.close();
out = null;
} catch (IOException e) {
throw new RuntimeException(e);
}
if (in != null)
try {
in.close();
in = null;
} catch (IOException e) {
throw new RuntimeException(e);
}
}
return dist;
}
}Bean a = new Bean("lzy", new ChildBean("child"));
Bean b = BeanUtil.cloneTo(a);
Log.i(TAG, "onCreate: " + (a.getChildBean() == b.getChildBean())); //false
Log.i(TAG, "onCreate: " + (a.getChildBean().equals(b.getChildBean()))); //true這樣就可以很輕松的得到我們預(yù)期的結(jié)果，但是記得每一個(gè)類都要去 實(shí)現(xiàn)Serializable接口。
Cloneable和Serializable一樣都是標(biāo)記型接口，它們內(nèi)部都沒有方法和屬性，implements Cloneable表示該對象能被克隆，能使用Object.clone()方法。如果沒有implements Cloneable的類調(diào)用Object.clone()方法就會拋出CloneNotSupportedException。
(1)淺克隆（shallow clone），淺拷貝是指拷貝對象時(shí)僅僅拷貝對象本身和對象中的基本變量，而不拷貝對象包含的引用指向的對象。
(2)深克隆（deep clone），深拷貝不僅拷貝對象本身，而且拷貝對象包含的引用指向的所有對象。
舉例區(qū)別一下：對象A1中包含對B1的引用，B1中包含對C1的引用。淺拷貝A1得到A2，A2中依然包含對B1的引用，B1中依然包含對C1的引用。深拷貝則是對淺拷貝的遞歸，深拷貝A1得到A2，A2中包含對B2（B1的copy）的引用，B2中包含對C2（C1的copy）的引用。
要讓一個(gè)對象進(jìn)行克隆，其實(shí)就是兩個(gè)步驟：
1.讓該類實(shí)現(xiàn)java.lang.Cloneable接口；
2.重寫（override）Object類的clone()方法。
public class Wife implements Cloneable {
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Wife(int id,String name) {
this.id = id;
this.name = name;
}
@Override
public int hashCode() {//myeclipse自動生成的
final int prime = 31;
int result = 1;
result = prime * result + id;
result = prime * result + ((name == null) ? 0 : name.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {//myeclipse自動生成的
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Wife other = (Wife) obj;
if (id != other.id)
return false;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
/**
* @param args
* @throws CloneNotSupportedException
*/
public static void main(String[] args) throws CloneNotSupportedException {
Wife wife = new Wife(1,"wang");
Wife wife2 = null;
wife2 = (Wife) wife.clone();
System.out.println("class same="+(wife.getClass()==wife2.getClass()));//true
System.out.println("object same="+(wife==wife2));//false
System.out.println("object equals="+(wife.equals(wife2)));//true
}
}public class Husband implements Cloneable {
private int id;
private Wife wife;
public Wife getWife() {
return wife;
}
public void setWife(Wife wife) {
this.wife = wife;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public Husband(int id) {
this.id = id;
}
@Override
public int hashCode() {//myeclipse自動生成的
final int prime = 31;
int result = 1;
result = prime * result + id;
return result;
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
@Override
public boolean equals(Object obj) {//myeclipse自動生成的
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Husband other = (Husband) obj;
if (id != other.id)
return false;
return true;
}
/**
* @param args
* @throws CloneNotSupportedException
*/
public static void main(String[] args) throws CloneNotSupportedException {
Wife wife = new Wife(1,"jin");
Husband husband = new Husband(1);
Husband husband2 = null;
husband.setWife(wife);
husband2 = (Husband) husband.clone();
System.out.println("husband class same="+(husband.getClass()==husband2.getClass()));//true
System.out.println("husband object same="+(husband==husband2));//false
System.out.println("husband object equals="+(husband.equals(husband)));//true
System.out.println("wife class same="+(husband.getWife().getClass()==husband2.getWife().getClass()));//true
System.out.println("wife object same="+(husband.getWife()==husband2.getWife()));//true
System.out.println("wife object equals="+(husband.getWife().equals(husband.getWife())));//true
}
}如果要深克隆，需要重寫（override）Object類的clone()方法，并且在方法內(nèi)部調(diào)用持有對象的clone()方法；注意如下代碼的clone()方法
public class Husband implements Cloneable {
private int id;
private Wife wife;
public Wife getWife() {
return wife;
}
public void setWife(Wife wife) {
this.wife = wife;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public Husband(int id) {
this.id = id;
}
@Override
public int hashCode() {//myeclipse自動生成的
final int prime = 31;
int result = 1;
result = prime * result + id;
return result;
}
@Override
protected Object clone() throws CloneNotSupportedException {
Husband husband = (Husband) super.clone();
husband.wife = (Wife) husband.getWife().clone();
return husband;
}
@Override
public boolean equals(Object obj) {//myeclipse自動生成的
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Husband other = (Husband) obj;
if (id != other.id)
return false;
return true;
}
/**
* @param args
* @throws CloneNotSupportedException
*/
public static void main(String[] args) throws CloneNotSupportedException {
Wife wife = new Wife(1,"jin");
Husband husband = new Husband(1);
Husband husband2 = null;
husband.setWife(wife);
husband2 = (Husband) husband.clone();
System.out.println("husband class same="+(husband.getClass()==husband2.getClass()));//true
System.out.println("husband object same="+(husband==husband2));//false
System.out.println("husband object equals="+(husband.equals(husband)));//true
System.out.println("wife class same="+(husband.getWife().getClass()==husband2.getWife().getClass()));//true
System.out.println("wife object same="+(husband.getWife()==husband2.getWife()));//false
System.out.println("wife object equals="+(husband.getWife().equals(husband.getWife())));//true
}
}但是也有不足之處，如果Husband內(nèi)有N個(gè)對象屬性，突然改變了類的結(jié)構(gòu)，還要重新修改clone()方法。
解決辦法：可以使用Serializable運(yùn)用反序列化手段，調(diào)用java.io.ObjectInputStream對象的 readObject()方法。
“Java中的clone()和Cloneable接口使用方法是什么”的內(nèi)容就介紹到這里了，感謝大家的閱讀。如果想了解更多行業(yè)相關(guān)的知識可以關(guān)注億速云網(wǎng)站，小編將為大家輸出更多高質(zhì)量的實(shí)用文章！
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