java中的clone小结

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基本概念

浅克隆：创建一个新对象，新对象的属性和原来对象完全相同，对于非基本类型属性，仍指向原有属性所指向的对象的内存地址。

深克隆：创建一个新对象，属性中引用的其他对象也会被克隆，不再指向原有对象地址。

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测试类

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public static void main(String[] args) throws Exception{
	// 创建父亲(LiLiu)，儿子(LiWu)，孙子（LiLiu）并关联
	Son father = new Son();
	father.setName("LiSi");
	Son son = new Son();
	son.setName("LiWu");
	Son grandSon = new Son();
	grandSon.setName("LiLiu");
	father.setSon(son);
	son.setSon(grandSon);
	// 调用clone方法
	Son fatherCopy =  (Son) father.clone();
	boolean flag1 = fatherCopy==father;
	boolean flag2 = fatherCopy.getSon() == son;
	boolean flag3 = fatherCopy.getSon().getSon() == grandSon;
	// 比较克隆后的地址
	System.out.println(flag1);// false
	System.out.println(flag2);// true
	System.out.println(flag3);// true
	// 比较Name
	flag1= fatherCopy.getName()==father.getName();
	flag2 = fatherCopy.getSon().getName() == son.getName();
	flag3 = fatherCopy.getSon().getSon().getName() == grandSon.getName();
	System.out.println(flag1);// true
	System.out.println(flag2);// true
	System.out.println(flag3);// true
	
	//将对象写到流里    
	ByteArrayOutputStream byteOut=new ByteArrayOutputStream();    
	ObjectOutputStream objOut=new ObjectOutputStream(byteOut);    
	objOut.writeObject(father);
	//从流里读出来    
	ByteArrayInputStream byteIn=new ByteArrayInputStream(byteOut.toByteArray());    
	ObjectInputStream objInput=new ObjectInputStream(byteIn);
    fatherCopy = (Son) objInput.readObject();
	flag1= fatherCopy==father;
	flag2 = fatherCopy.getSon() == son;
	flag3 = fatherCopy.getSon().getSon() == grandSon;
	System.out.println(flag1);// false
	System.out.println(flag2);// false
	System.out.println(flag3);// false
	
	// 比较Name
	flag1= fatherCopy.getName()==father.getName();
	flag2 = fatherCopy.getSon().getName() == son.getName();
	flag3 = fatherCopy.getSon().getSon().getName() == grandSon.getName();
	System.out.println(flag1);// false
	System.out.println(flag2);// false
	System.out.println(flag3);// false
}

从上文代码及运行结果不难看出，如果对象实现Cloneable并重写clone方法不进行任何操作时,调用clone是进行的浅克隆。而使用对象流将对象写入流然后再读出是进行的深克隆。

工具类

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public class CloneUtils {
  
    private static final Logger LOG = LoggerFactory.getLogger(CloneUtils.class);

    private CloneUtils{}

    public static <T extends Serializable> T clone(T obj){
        T cloneObj = null;
        ByteArrayOutputStream out = null;
        ByteArrayInputStream in = null;
        
        try{
            
            out = new ByteArrayOutputStream();
            ObjectOutputStream obs = new ObjectOutputStream(out);
            obs.writeObject(obj);
            obs.close();

            ios = new ByteArrayInputStream(out.toByteArray());
            ObjectInputStream ois = new ObjectInputStream(ios);
            cloneObj = (T)ois.readObject();
            ois.close();

        }catch(Exception ex){
            LOG.error("拷贝对象时发生异常", e1);
        }finally{
            try(){
                if(null != out){
                    out.close();
                }
                if(null != in){
                    in.close();
                }
            }catch(Exception ex){
                LOG.warn("关闭字节流时发生异常", e2);
            }
        }

    }

}

参考文献

  1. https://www.cnblogs.com/liqiangchn/p/9465186.html