java - 深拷贝 浅拷贝

一.定义

1.浅拷贝

1.定义

浅拷贝只复制对象的引用，不复制引用指向的实际对象。对基本数据类型复制值，对引用类型的值复制其引用。

2.实现方法

通过重写Object类的clone()方法，并让类实现Cloneable接口

3.代码示例

// 浅拷贝
public class Student implements Cloneable{int age;String name;@Overrideprotected Object clone() throws CloneNotSupportedException {return super.clone();}
}

2.深拷贝

1.定义

深拷贝不止复制对象本身，还递归复制对象中所有引用的对象，使新对象和旧对象之间完全独立

2.实现方法

1.让所有嵌套的引用类型也实现 Cloneable 接口并重写 clone()，在顶层对象的 clone() 中递归调用嵌套对象的 clone()。

2.通过序列化将对象写入流，再从流中读取，序列化方式简单易用，但性能较低

3.代码示例

1.递归调用

class Address implements Cloneable {String city;public Address(String city) {this.city = city;}@Overrideprotected Object clone() throws CloneNotSupportedException {return super.clone();}
}class Person implements Cloneable {String name;Address addr; public Person(String name, Address addr) {this.name = name;this.addr = addr;}@Overrideprotected Object clone() throws CloneNotSupportedException {Person copy = (Person) super.clone();copy.addr = (Address) this.addr.clone(); return copy;}
}

2.序列化

class Address implements Serializable {String city;public Address(String city) {this.city = city;}
}class Person implements Serializable {String name;Address addr;public Person(String name, Address addr) {this.name = name;this.addr = addr;}Person deepCopy() throws Exception {// 写入字节流ByteArrayOutputStream bos = new ByteArrayOutputStream();ObjectOutputStream oos = new ObjectOutputStream(bos);oos.writeObject(this);// 将字节序列恢复为新对象ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bos.toByteArray()));return (Person) ois.readObject();}
}