java语言之Cloneable接口

在我们学习过程中，会发现java很多非常重要的接口，比如Cloneable，Serializable，Comparable等等之类的，今天我就总结一下Cloneable接口。

我学习到现在觉得最好的学习资源就是源码以及源码的注释，任何其他的都是对源码的翻译和解读，现在我就说说我对源码及注释的理解，如何大家想从源头上获取，建议大家看Cloneable接口和Object中的clone()方法。

正文：

1.如果一个对象要实现拷贝，就必须要实现Cloneable接口，只有实现了该接口，该类的对象采用拷贝的能力，否则调用clone()是会抛出CloneNotSupportedException异常

2.拷贝分为浅拷贝和深拷贝

浅拷贝是拷贝的默认方式(逐个field拷贝)，只适用于基本数据类型和不可变类型(如String)

深拷贝是适用于有引用成员变量的情形，因为浅拷贝在拷贝应用成员变量时只是拷贝了引用，所以要自己特别处理，若不处理拷贝出来的对象都是公用一块内存(一变都变)

例子：

浅拷贝：

public class Resume_ShallowCopy implements Cloneable {
    private String name;
    private String sex;
    private String age;
    private String timeArea;
    private String company;

    public Resume_ShallowCopy(String name) {
        this.name = name;
    }

    public void setPersonalInfo(String sex, String age) {
        this.sex = sex;
        this.age = age;
    }

    public void setWorkExperience(String timeArea, String company) {
        this.timeArea = timeArea;
        this.company = company;
    }

    public void display() {
        System.out.println(name + ", " + sex + ", " + age);
        System.out.println("工作经历：" + timeArea + ", " + company);
        System.out.println(age.hashCode());
        System.out.println();
    }
}

深拷贝：

public class Resume_DeepCopy implements Cloneable {
    private String         name;
    private String         sex;
    private String         age;

    private WorkExperience work; // 引用类型

    public Resume_DeepCopy(String name) {
        this.name = name;
        work = new WorkExperience();
    }

    public Resume_DeepCopy(WorkExperience work) throws CloneNotSupportedException {
        this.work = (WorkExperience) work.clone();
    }

    public void setPersonalInfo(String sex, String age) {
        this.sex = sex;
        this.age = age;
    }

    public void setWork(String workDate, String company) {
        work.setWorkDate(workDate);
        work.setCompany(company);
    }

    public void display() {
        System.out.println(name + ", " + sex + ", " + age);
        System.out.println("工作经历：" + work.getWorkData() + " " + work.getCompany());
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Resume_DeepCopy obj = new Resume_DeepCopy(work);//把work拷贝一下
        obj.name = name;// 逐个拷贝
        obj.sex = sex;
        obj.age = age;
        return obj;
    }
}

引用类型：

public class WorkExperience implements Cloneable {
    private String workDate;
    private String company;

    public String getWorkData() {
        return workDate;
    }

    public void setWorkDate(String workData) {
        this.workDate = workData;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

Main:

public class Console {
    public static void main(String[] args) throws CloneNotSupportedException {
        Resume_DeepCopy a = new Resume_DeepCopy("大鸟");
        a.setPersonalInfo("男", "29");
        a.setWork("1998-2000", "XX公司");

        Resume_DeepCopy b = (Resume_DeepCopy) a.clone();
        b.setWork("1998-2006", "YY企业");

        Resume_DeepCopy c = (Resume_DeepCopy) a.clone();
        c.setPersonalInfo("男", "24");
        c.setWork("1998-2003", "ZZ企业");

        a.display();
        b.display();
        c.display();
    }
}

拷贝还设计到一个设计模式：原型模式~~~ 有兴趣自己看~~~