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();  
}