Java中的克隆功能的应用

在JAVA中对象的克隆有的时候是必要的，克隆分两种：浅克隆、深克隆。

 

 

浅克隆 指如果对象中含有非基本类型的成员，那么克隆的对象与源对象共用该成员的引用，即在两个对象中该成员的引用是一样的。这种克隆是相对意义上的克隆，克隆的对象与源对象并没有绝对的独立。

 

深克隆 指克隆的对象与源对象在所有的成员上都有不同引用，实现了绝对意义上的克隆。浅克隆比起深克隆来很容易实现。下面先说浅克隆。

浅克隆的实现 ：待克隆的类需实现java.lang.Cloneable接口，该接口无待实现的方法，只是一种标记。然后覆盖Object类的clone()方法，在方法中调用Object的clone()方法即可。

 

深 克隆的实现 ：把此方法放到要克隆的对象中，并使被克隆的对象以及引用到的对象实现java.io.Serializable接口。

public Object clone() throws CloneNotSupportedException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream oos = null;
        try {
            oos = new ObjectOutputStream(bos);
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            oos.writeObject(this);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (NullPointerException e) {
            e.printStackTrace();
        }

        // 将流序列化成对象
        ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
        ObjectInputStream ois = null;
        try {
            ois = new ObjectInputStream(bis);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (NullPointerException e) {
            e.printStackTrace();
        }

        try {
            return ois.readObject();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (NullPointerException e) {
            e.printStackTrace();
        }

        return null;
        // return super.clone();
    }

深克隆例子 ：

 

package com.javaeye.xiaobian;

import java.io.Serializable;

public class Teacher implements Serializable {
	public int age;
	public String name;
	private Result result;

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getName() {
		return name;
	}

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

	public Result getResult() {
		return result;
	}

	public void setResult(Result result) {
		this.result = result;
	}

}

 

package com.javaeye.xiaobian;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class Student implements Cloneable, Serializable {

	public int age;
	public String name;
	public Teacher teacher;

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getName() {
		return name;
	}

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

	public Teacher getTeacher() {
		return teacher;
	}

	public void setTeacher(Teacher teacher) {
		this.teacher = teacher;
	}

	public Object clone() throws CloneNotSupportedException {
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
		ObjectOutputStream oos = null;
		try {
			oos = new ObjectOutputStream(bos);
		} catch (IOException e) {
			e.printStackTrace();
		}
		try {
			oos.writeObject(this);
		} catch (IOException e) {
			e.printStackTrace();
		} catch (NullPointerException e) {
			e.printStackTrace();
		}

		// 将流序列化成对象
		ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
		ObjectInputStream ois = null;
		try {
			ois = new ObjectInputStream(bis);
		} catch (IOException e) {
			e.printStackTrace();
		} catch (NullPointerException e) {
			e.printStackTrace();
		}

		try {
			return ois.readObject();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (NullPointerException e) {
			e.printStackTrace();
		}

		return null;
		// return super.clone();
	}

}

 

package com.javaeye.xiaobian;

import java.io.Serializable;

public class Result implements Serializable {
	private long numeric = 100;

	public long getNumeric() {
		return numeric;
	}

	public void setNumeric(long numeric) {
		this.numeric = numeric;
	}
package com.javaeye.xiaobian;

public class Test {

	/**
	 * @param args
	 * @throws CloneNotSupportedException
	 */
	public static void main(String[] args) throws CloneNotSupportedException {
		// TODO Auto-generated method stub
		Result result = new Result();
		result.setNumeric(101);

		Teacher teacher = new Teacher();
		teacher.setAge(26);
		teacher.setName("xiaobian.iteye.com");
		teacher.setResult(result);
		Object c;
		Student student = new Student();
		student.setAge(20);
		student.setName("xiaobian.iteye.com");
		student.setTeacher(teacher);

		Student student1 = (Student) student.clone();
		// 克隆后未修改引用数据之前
		System.out.println(student.getTeacher().getResult().getNumeric());
		System.out.println(student1.getTeacher().getResult().getNumeric());

		// 克隆后修改引用数据之后
		student1.getTeacher().getResult().setNumeric(100);

		System.out.println(student.getTeacher().getResult().getNumeric());
		System.out.println(student1.getTeacher().getResult().getNumeric());

	}
}
 
}

 

测试输入出的结果：

 

101
101

101
100

 

浅克隆的例子 ：

package com.javaeye.xiaobian;

public class Student implements Cloneable {

	public int age;
	public String name;
	public Teacher teacher;

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getName() {
		return name;
	}

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

	public Teacher getTeacher() {
		return teacher;
	}

	public void setTeacher(Teacher teacher) {
		this.teacher = teacher;
	}

	public Object clone() throws CloneNotSupportedException {

		return super.clone();
	}

}

 

package com.javaeye.xiaobian;


public class Teacher {
	public int age;
	public String name;
	private Result result;

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getName() {
		return name;
	}

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

	public Result getResult() {
		return result;
	}

	public void setResult(Result result) {
		this.result = result;
	}

}

 

package com.javaeye.xiaobian;


public class Result {
	private long numeric = 100;

	public long getNumeric() {
		return numeric;
	}

	public void setNumeric(long numeric) {
		this.numeric = numeric;
	}

}

 

package com.javaeye.xiaobian;

public class Test {

	/**
	 * @param args
	 * @throws CloneNotSupportedException
	 */
	public static void main(String[] args) throws CloneNotSupportedException {
		// TODO Auto-generated method stub
		Result result = new Result();
		result.setNumeric(101);

		Teacher teacher = new Teacher();
		teacher.setAge(26);
		teacher.setName("xiaobian.iteye.com");
		teacher.setResult(result);
		Student student = new Student();
		student.setAge(20);
		student.setName("xiaobian.iteye.com");
		student.setTeacher(teacher);

		Student student1 = (Student) student.clone();
		// 克隆后未修改引用数据之前
		System.out.println(student.getTeacher().getResult().getNumeric());
		System.out.println(student1.getTeacher().getResult().getNumeric());

		// 克隆后修改引用数据之后
		student1.getTeacher().getResult().setNumeric(100);

		System.out.println(student.getTeacher().getResult().getNumeric());
		System.out.println(student1.getTeacher().getResult().getNumeric());

	}
}

 

测试结果：

101
101

 

100
100