Java对象clone()的测试

Object中自带native clone()方法.

研究了一下用法.

 public class DeepCopyTest {

     public static void main(String[] args) throws CloneNotSupportedException {

         test1();
         System.out.println("-----------------------------");
         test2();

     }

     static void test1() throws CloneNotSupportedException {
         Teacher t1 = new Teacher();
         t1.settName("LaoLi");

         Teacher t2 = new Teacher();
         t2.settName("LaoWang");

         Stu stu = new Stu();
         stu.setName("name_1");
         stu.setAge(23);
         stu.setScore(129);
         stu.setTeacher(t1);

         Stu stuCopy = stu.clone();
         System.out.println("1:" + stu.toString());
         System.out.println("2:" + stuCopy.toString());

         stuCopy.setName("name_2");
         stuCopy.setAge(25);
         stuCopy.setScore(133);
         stuCopy.setTeacher(t2);

         System.out.println("11:" + stu.toString());
         System.out.println("22:" + stuCopy.toString());

     }

     static void test2() throws CloneNotSupportedException {
         Teacher t1 = new Teacher();
         t1.settName("LaoLi");

         Teacher t2 = new Teacher();
         t2.settName("LaoWang");

         Stu stu = new Stu();
         stu.setName("name_1");
         stu.setAge(23);
         stu.setScore(129);
         stu.setTeacher(t1);

         Stu stuCopy = stu.clone();
         System.out.println("1:" + stu.toString());
         System.out.println("2:" + stuCopy.toString());

         stuCopy.setName("name_2");
         stuCopy.setAge(25);
         stuCopy.setScore(133);
         stuCopy.getTeacher().settName("LaoKong");

         System.out.println("11:" + stu.toString());
         System.out.println("22:" + stuCopy.toString());

     }

 }

 class Teacher {
     private String tName;

     public String gettName() {
         return tName;
     }

     public void settName(String tName) {
         this.tName = tName;
     }

     @Override
     public String toString() {
         return ToStringBuilder.reflectionToString(this, ToStringStyle.SHORT_PREFIX_STYLE);
     }
 }

 class Stu implements Cloneable {
     private String name;
     private int age;
     private Integer score;
     private Teacher teacher;

     public Teacher getTeacher() {
         return teacher;
     }

     public void setTeacher(Teacher teacher) {
         this.teacher = teacher;
     }

     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name = name;
     }

     public int getAge() {
         return age;
     }

     public void setAge(int age) {
         this.age = age;
     }

     public Integer getScore() {
         return score;
     }

     public void setScore(Integer score) {
         this.score = score;
     }

     public Stu clone() throws CloneNotSupportedException {
         return (Stu) super.clone();
     }

     @Override
     public String toString() {
         return ToStringBuilder.reflectionToString(this, ToStringStyle.SHORT_PREFIX_STYLE);
     }

 }

执行结果:

1:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoLi]]
2:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoLi]]
11:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoLi]]
22:Stu[name=name_2,age=25,score=133,teacher=Teacher[tName=LaoWang]]
-----------------------------
1:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoLi]]
2:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoLi]]
11:Stu[name=name_1,age=23,score=129,teacher=Teacher[tName=LaoKong]]
22:Stu[name=name_2,age=25,score=133,teacher=Teacher[tName=LaoKong]]

基本验证了这样的结论:

基本类型,不变类型可以做到值拷贝效果.不变类型其实是引用发生了变化.

对象类型,实际上是引用拷贝.

设置一个新对象,stuCopy.getTeacher().setName("LaoKong")

引用其实发生了变化.-->指针A指向空间KK, 指针B也指向空间KK, 指针指向的地址KK中的内容替换掉.

而把对象重新设值, stuCopy.setTeacher(t2)

其实是把对象引用的地址指向新的对象. -->指针A指向空间KK, 指针B也指向空间KK, 指针BB指向新的空间KKK.

----------------------------------------------------

/* 浅复制 */
public Object clone() throws CloneNotSupportedException {
    Prototype proto = (Prototype) super.clone();
    return proto;
}  

/* 深复制 */
public Object deepClone() throws IOException, ClassNotFoundException {  

    /* 写入当前对象的二进制流 */
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    ObjectOutputStream oos = new ObjectOutputStream(bos);
    oos.writeObject(this);  

    /* 读出二进制流产生的新对象 */
    ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
    ObjectInputStream ois = new ObjectInputStream(bis);
    return ois.readObject();
}