我试图了解Object类的clone()方法的工作原理 . Object类中的注释表示' this method performs a "shallow copy" of this object, not a "deep copy" operation. '
以下是我对Shallow&Deep copy的理解..
浅拷贝尽可能少复制 . 集合的浅表副本是集合结构的副本,而不是元素 . 通过浅拷贝,两个集合现在共享各个元素 . 深拷贝复制一切 . 集合的深层副本是两个集合,原始集合中的所有元素都是重复的 .
因此,如果我克隆一个Object并修改其克隆上的任何可变元素,那么同样应该反映在创建克隆的第一个对象上,因为它们共享相同的内存 . 为了测试这个,我创建了3个类......
一个简单的pojo ..
package test.clone;
import java.util.Arrays;
public class Misc implements Cloneable{
private String value;
public Misc(String value) {
super();
this.value = value;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
@Override
public String toString() {
return "Misc [value=" + value + "]";
}
protected Misc clone() throws CloneNotSupportedException{
return (Misc)super.clone();
}
}
需要克隆的类..
package test.clone;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class Victim implements Cloneable{
private String name = "Renjith";
private String[] educationList = {"EDU_1", "EDU_2", "EDU_3", "EDU_4"};
private Misc[] miscList = {new Misc("1"), new Misc("2")};
private List<Misc> miscList2 = new ArrayList<Misc>(Arrays.asList(miscList));
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String[] getEducationList() {
return educationList;
}
public void setEducationList(String[] educationList) {
this.educationList = educationList;
}
protected Victim clone() throws CloneNotSupportedException{
return (Victim)super.clone();
}
public Misc[] getMiscList() {
return miscList;
}
public void setMiscList(Misc[] miscList) {
this.miscList = miscList;
}
public List<Misc> getMiscList2() {
return miscList2;
}
public void setMiscList2(List<Misc> miscList2) {
this.miscList2 = miscList2;
}
@Override
public String toString() {
return "Victim [name=" + name + ", educationList="
+ Arrays.toString(educationList) + ", miscList="
+ Arrays.toString(miscList) + ", miscList2=" + miscList2 + "]";
}
}
进行克隆的主要类......和修改......
public class Main {
public static void main(String[] args) throws CloneNotSupportedException {
Victim victim = new Victim();
System.out.println(victim);
Victim secondVictim = victim.clone();
String[] educationList = {"EDU_1_mod", "EDU_2_mod", "EDU_3_mod", "EDU_4_mod"};
Misc[] miscList = {new Misc("3"), new Misc("4")};
List<Misc> miscList2 = new ArrayList<Misc>(Arrays.asList(miscList));
secondVictim.setEducationList(educationList);
secondVictim.setMiscList(miscList);
secondVictim.setMiscList2(miscList2);
System.out.println(secondVictim);
System.out.println(victim);
}
}
我期待输出如下......
受害者[name = Renjith,educationList = [EDU_1,EDU_2,EDU_3,EDU_4],miscList = [Misc [value = 1],Misc [value = 2]],miscList2 = [Misc [value = 1],Misc [value] = 2]]]受害者[name = Renjith,educationList = [EDU_1_mod,EDU_2_mod,EDU_3_mod,EDU_4_mod],miscList = [Misc [value = 3],Misc [value = 4]],miscList2 = [Misc [value = 3] ,Misc [value = 4]]]受害者[name = Renjith,educationList = [EDU_1,EDU_2,EDU_3,EDU_4],miscList = [Misc [value = 3],Misc [value = 4]],miscList2 = [Misc [值= 3],杂项[value = 4]]]
但我得到......
受害者[name = Renjith,educationList = [EDU_1,EDU_2,EDU_3,EDU_4],miscList = [Misc [value = 1],Misc [value = 2]],miscList2 = [Misc [value = 1],Misc [value] = 2]]]受害者[name = Renjith,educationList = [EDU_1_mod,EDU_2_mod,EDU_3_mod,EDU_4_mod],miscList = [Misc [value = 3],Misc [value = 4]],miscList2 = [Misc [value = 3] ,Misc [value = 4]]]受害者[name = Renjith,educationList = [EDU_1,EDU_2,EDU_3,EDU_4],miscList = [Misc [value = 1],Misc [value = 2]],miscList2 = [Misc [值= 1],杂项[value = 2]]]
谁能告诉我这有什么问题?
我已经经历了Understanding Object.clone() in Java,但仍然无法理解....
1 回答
您没有修改列表/数组,而是用新引用替换它们 . 尝试像这样更新你的setter:
这应该修改共享对象,从而产生预期的输出 .