Posted on 2008-08-02 07:16
梦与桥 阅读(178)
评论(0) 编辑 收藏 所属分类:
java基础
1、目的：为了获得对象的一份拷贝。
2、一般步骤：§在派生类中覆盖基类（object)的clone方法，并声明为public
§在派生类的克隆方法中调用super.clone()
§在派生类中实现Cloneable接口
3、分类：浅拷贝、深拷贝
§浅拷贝仅仅拷贝所考虑的对象，而不拷贝它所引用的对象
§深拷贝把要拷贝的对象所引用的对象都拷贝了一遍
4、浅拷贝实例：
class Book implements Cloneable
{
private String name;
private double price;
public Author author;
Book(String name,double price,Author author)
{
this.name=name;
this.price=price;
this.author=author;
}
public String toString()
{
return "book's name:"+name+"\t\tbook's price:"+price+author.tostring();
}
public Object clone()
{
Object o=null;
try
{
o=super.clone();
}
catch (CloneNotSupportedException e)
{
System.out.println(e.toString());
}
return o;
}
}
class Author
{
private String name;
private int age;
Author(String name,int age)
{
this.name=name;
this.age=age;
}
public void set(String name,int age)
{
this.name=name;
this.age=age;
}
public String tostring()
{
return "\nauthor's name:"+name+"\t\tauthor's age"+age;
}
}
public class Test
{
public static void main(String args[])
{
Author author=new Author("孙悟空",800);
Book book1=new Book("高等数学",32.00,author);
Book book2=(Book)book1.clone();
book1.author.set("唐僧",700);//此处的修改影响到了book2，体现了浅拷贝的特点
System.out.println(book2);
}
}
5、深拷贝实例：
class Book implements Cloneable
{
private String name;
private double price;
public Author author;
Book(String name,double price,Author author)
{
this.name=name;
this.price=price;
this.author=author;
}
public String toString()
{
return "book's name:"+name+"\t\tbook's price:"+price+author.tostring();
}
public Object clone()
{
Book o=null;
try
{
o=(Book)super.clone();
}
catch (CloneNotSupportedException e)
{
System.out.println(e.toString());
}
o.author=(Author)author.clone();
return o;
}
}
class Author implements Cloneable
{
private String name;
private int age;
Author(String name,int age)
{
this.name=name;
this.age=age;
}
public void set(String name,int age)
{
this.name=name;
this.age=age;
}
public String tostring()
{
return "\nauthor's name:"+name+"\t\tauthor's age"+age;
}
public Object clone()
{
Object o=null;
try
{
o=super.clone();
}
catch (CloneNotSupportedException e)
{
System.out.println(e.toString());
}
return o;
}
}
public class Test
{
public static void main(String args[])
{
Author author=new Author("孙悟空",800);
Book book1=new Book("高等数学",32.00,author);
Book book2=(Book)book1.clone();
book1.author.set("唐僧",700);//此处的修改没有影响book2，体现了深拷贝的特点。
System.out.println(book2);
}
}
6、注意：
§在派生类中覆盖Object的clone()方法时，一定要调用super.clone()，因为在运行时刻，Object中的clone()识别出你要复制的是哪一个对象，然后为此对象分配空间，并进行对象的复制，将原始对象的内容一一复制到新对象的存储空间中。
§在Object.clone()正式开始操作前，首先会检查一个类是否Cloneable，即是否具有克隆能力——换言之，它是否实现了Cloneable接口。若未实现，Object.clone()就掷出一个CloneNotSupportedException违例，指出我们不能克隆它。