java 深浅拷贝（克隆）

一、重写clone方法

克隆一个对象，该对象要实现克隆接口，即 implements Cloneable，重写克隆方法

如下代码：

public class Teacher implements Cloneable {

    public int getTno() {
		return tno;
	}
	public void setTno(int tno) {
		this.tno = tno;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	private int tno;
    private String name;
    
    @Override
    protected Object clone() {
        Teacher teacher = null;
        try {
            teacher = (Teacher)super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return teacher;
    }
  
}

当里面有更深层的引用的时候，被引用的类也实现克隆方法， 如下：学生引用老师，如果想实现深拷贝，要重写学生类的克隆方法。

import org.junit.Test;

public class Student implements Cloneable{


    public int getSno() {
		return sno;
	}

	public void setSno(int sno) {
		this.sno = sno;
	}

	public String getName() {
		return name;
	}

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

	private int sno ;
    private String name;
    public Teacher getTeacher() {
		return teacher;
	}

	public void setTeacher(Teacher teacher) {
		this.teacher = teacher;
	}
    // 引用老师
	private Teacher teacher;



    @Override
    public Object clone() throws CloneNotSupportedException {
        Student s = null;
        try{
            s = (Student)super.clone();
            // 引用也克隆和设置下
            Teacher t = (Teacher)this.teacher.clone();
            s.setTeacher(t);
        }catch (Exception e){
            e.printStackTrace();
        }
        return s;
    }

}

二、序列化实现克隆

//工具方法
　　public Object cloneObject(Object object) throws IOException, ClassNotFoundException {
        //将对象序列化
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);
        objectOutputStream.writeObject(object);

        //将字节反序列化
        ByteArrayInputStream inputStream = new ByteArrayInputStream(outputStream.toByteArray());
        ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);
        Object obj = objectInputStream.readObject();

        return obj;
    }

重写clone方法 与 通过序列化 两种拷贝方式比较:

clone方法:

优点:速度快,效率高

缺点:在对象引用比较深时,使用此方式比较繁琐

 

通过序列化:

优点:非常简便的就可以完成深度copy

缺点:由于序列化的过程需要跟磁盘打交道,因此效率会低于clone方式

 

如何抉择?

实际开发中,根据两种方式的优缺点进行选择即可!

 

参考原文：https://www.cnblogs.com/lzzRye/p/9459465.html