首先,我们需要知道的是,什么是对象克隆?对象克隆是当程序运行时,可能需要一个新对象,用来保存当前对象的状态,并且新的对象与当前对象没有任何关联,即我改变了新对象属性的值,而当前对象没有发生改变。而这新的对象,就是对当前对象的克隆,或者说拷贝。
要完成对象克隆,有以下要求:
1. 新的对象与当前对象值相同
2. 新的对象与当前对象的引用地址不同
要实现对象克隆,有以下步骤:
1. 对要被对象克隆的对应类继承Cloneable接口,并重载clone方法,将访问权限改成public
2. 将当前对象的clone方法赋值给新的对象,完成对象克隆。
public class Test implements Cloneable{
public int a;
public int b;
private int c;
private int d;
public String aa;
private String bb;
public TestIn testIn = new TestIn();
public TestIns testIns = new TestIns();
@Override
public Object clone() throws CloneNotSupportedException {
// TODO Auto-generated method stub
return super.clone();
}
public Test(){}
public Test(int a,int b,int c,int d){
this.a=a;
this.b=b;
this.c=c;
this.d=d;
}
private Test(int c,int d){
this.c=c;
this.d=d;
}
public int getA() {
return a;
}
public void setA(int a) {
this.a = a;
}
public int getB() {
return b;
}
public void setB(int b) {
this.b = b;
}
public int getC() {
return c;
}
public void setC(int c) {
this.c = c;
}
public int getD() {
return d;
}
public void setD(int d) {
this.d = d;
}
private void A(){
System.out.println("哈哈哈");
}
public void B(){
System.out.println("fdsa");
}
public String getAa() {
return aa;
}
public void setAa(String aa) {
this.aa = aa;
}
public String getBb() {
return bb;
}
public void setBb(String bb) {
this.bb = bb;
}
@Override
public String toString() {
return "Test [a=" + a + ", b=" + b + ", c=" + c + ", d=" + d + ", aa=" + aa + ", bb=" + bb + "]";
}
class TestIn{
public String test_a;
public int test_b;
}
class TestIns{
public String test_a;
public int test_b;
}
}
Test test_1 = new Test();
Test test_2 = (Test) test_1.clone();
System.out.println("\r++++++++++拷贝(克隆)+++++++++++");
System.out.println("----------赋值前----------");
System.out.println("test_1:"+test_1);
System.out.println("test_2:"+test_2);
test_2.setA(4);
System.out.println("----------赋值基本类型----------");
System.out.println("test_1:"+test_1);
System.out.println("test_2:"+test_2);
System.out.println("类是否引用同个地址:"+(test_1 == test_2));
以上代码的运行结果为:
++++++++++拷贝(克隆)+++++++++++
----------赋值前----------
test_1:Test [a=2, b=0, c=0, d=0, aa=null, bb=null]
test_2:Test [a=2, b=0, c=0, d=0, aa=null, bb=null]
----------赋值基本类型----------
test_1:Test [a=2, b=0, c=0, d=0, aa=null, bb=null]
test_2:Test [a=4, b=0, c=0, d=0, aa=null, bb=null]
类是否引用同个地址:false
这样,我们就实现了对象的克隆,当然,仅仅只是针对当前对象基本类型的克隆,这种对象克隆我们称之为浅克隆。
而如果要实现基本数据类型以及引用类型的克隆,就需要深克隆。
在test类中,你们也可以看到,有两个类的对象,一个是TestIn类,一个是TestIns类,并且都初始化了,然而在浅克隆的情况下,他们指向的地址是一致的
System.out.println("类的引用类TestIn是否引用同个地址:"+(test_1.testIn == test_2.testIn));
System.out.println("类的引用类TestIns是否引用同个地址:"+(test_1.testIns == test_2.testIns));
其运行结果:
类的引用类TestIn是否引用同个地址:true
类的引用类TestIns是否引用同个地址:true
如何实现深克隆呢,其实实现深克隆和实现浅克隆的原理差不多,步骤如下:
1.被克隆的对象对应类要继承Cloneable接口,并重载clone方法
2.若被克隆的对象里,有属性为被克隆的对象,则需要重写clone方法
3. 将当前对象的clone方法赋值给新的对象,完成对象深克隆。
以下代码我重写了Test的clone方法,并让对应类TestIns继承了Cloneable接口,重载clone方法
public class Test implements Cloneable{
public int a;
public int b;
private int c;
private int d;
public String aa;
private String bb;
public TestIn testIn = new TestIn();
public TestIns testIns = new TestIns();
@Override
public Object clone() throws CloneNotSupportedException {
// TODO Auto-generated method stub
Test test = (Test)super.clone();
test.testIns =(TestIns) this.testIns.clone();
return test;
}
public Test(){}
public Test(int a,int b,int c,int d){
this.a=a;
this.b=b;
this.c=c;
this.d=d;
}
private Test(int c,int d){
this.c=c;
this.d=d;
}
public int getA() {
return a;
}
public void setA(int a) {
this.a = a;
}
public int getB() {
return b;
}
public void setB(int b) {
this.b = b;
}
public int getC() {
return c;
}
public void setC(int c) {
this.c = c;
}
public int getD() {
return d;
}
public void setD(int d) {
this.d = d;
}
private void A(){
System.out.println("哈哈哈");
}
public void B(){
System.out.println("fdsa");
}
public String getAa() {
return aa;
}
public void setAa(String aa) {
this.aa = aa;
}
public String getBb() {
return bb;
}
public void setBb(String bb) {
this.bb = bb;
}
@Override
public String toString() {
return "Test [a=" + a + ", b=" + b + ", c=" + c + ", d=" + d + ", aa=" + aa + ", bb=" + bb + "]";
}
class TestIn{
public String test_a;
public int test_b;
}
class TestIns implements Cloneable{
public String test_a;
public int test_b;
@Override
protected Object clone() throws CloneNotSupportedException {
// TODO Auto-generated method stub
return super.clone();
}
}
}
System.out.println("类的引用类TestIn是否引用同个地址:"+(test_1.testIn == test_2.testIn));
System.out.println("类的引用类TestIns是否引用同个地址:"+(test_1.testIns == test_2.testIns));
运行效果如下:
类的引用类TestIn是否引用同个地址:true
类的引用类TestIns是否引用同个地址:false
有兴趣的可以去了解一下,为什么克隆有浅克隆和深克隆的区别:https://www.jianshu.com/p/b597f3e8269a
总结:无论是浅克隆还是深克隆,都需要将对应类继承Cloneable接口,并重载或者重写clone方法;浅克隆,只能克隆类的基本类型,而深克隆则可以克隆基本基本类型以及引用类型。
public class TestMain{
public static void main(String[] args){
Test test_1 = new Test();
Test test_2 = test_1;
System.out.println("++++++++++引用+++++++++++");
System.out.println("----------赋值前----------");
System.out.println("test_1:"+test_1);
System.out.println("test_2:"+test_2);
test_2.setA(2);
System.out.println("----------赋值后----------");
System.out.println("test_1:"+test_1);
System.out.println("test_2:"+test_2);
System.out.println("类是否引用同个地址:"+(test_1 == test_2));
try {
test_2 = (Test) test_1.clone();
System.out.println("\r++++++++++拷贝(克隆)+++++++++++");
System.out.println("----------赋值前----------");
System.out.println("test_1:"+test_1);
System.out.println("test_2:"+test_2);
test_2.setA(4);
System.out.println("----------赋值基本类型----------");
System.out.println("test_1:"+test_1);
System.out.println("test_2:"+test_2);
System.out.println("类是否引用同个地址:"+(test_1 == test_2));
System.out.println("类的引用类TestIn是否引用同个地址:"+(test_1.testIn == test_2.testIn));
System.out.println("类的引用类TestIns是否引用同个地址:"+(test_1.testIns == test_2.testIns));
} catch (CloneNotSupportedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
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