设计模式－原型模式

###原型模式 ####原型模式的优势 原型模式建立对象比直接使用new建立对象性能上要好许多,为Object类的clone方法是一个本地方法,它直接操做的是内存中的二进制流.原型模式简化建立对象的过程,使得建立对象像粘贴复制同样.

####使用场景 须要重复地建立类似对象时能够考虑使用原型模式,好比在一个循环体类建立对象.

####代码实现:

public class Prototype implements Cloneable{
    public Prototype clone(){
        Prototype prototype = null;
        try {
            prototype = (Prototype) super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return prototype;
    }
}

public class ConcretePrototype extends Prototype {
    public void show(){
        System.out.println("原型模式实现类:");
    }
}

public class Client {
    public static void main(String[] args) {
        ConcretePrototype cp = new ConcretePrototype();
        for (int i = 0; i < 10; i++) {
            ConcretePrototype clonecp = (ConcretePrototype) cp.clone();
            clonecp.show();
        }
    }
}

####原型模式的注意点

• 使用原型模式不会调用类的构造方法.

• 深拷贝和浅拷贝 浅拷贝: 对值类型的成员变量进行值的复制,对引用类型的成员变量只复制引用,不复制引用的对象. 深拷贝: 对值类型的成员变量进行值的复制,对引用类型的成员变量也进行引用对象的复制.

#####浅拷贝

import lombok.Data;
	@Data
	public class Student implements Cloneable{
	    private String studentName;
	    private Teacher teacher;

	    @Override
	    protected Student clone() throws CloneNotSupportedException {
	        return (Student) super.clone();
	    }

	    public Student(String studentName, Teacher teacher) {
	        this.studentName = studentName;
	        this.teacher = teacher;
	    }

	}

	@Data
	public class Teacher implements Serializable {
	    private static final long UID = 6948989635489677685L;

	    private String name;

	    public Teacher(String name) {
	        this.name = name;
	    }
	}

	public class Client {
	    public static void main(String[] args) throws Exception {
	        Teacher teacher = new Teacher("snail");
	        Student student1 = new Student("wjk",teacher);
	        Student student2 = (Student) student1.clone();
	        student2.getTeacher().setName("snail改变");
	        System.out.println(student1.getTeacher().getName());
	        System.out.println(student2.getTeacher().getName());
	     }
	}
	**运行结果**（拷贝的是引用）
	snail改变
	snail改变

#####深拷贝

@Data
	public class StudentSh implements Serializable {
	    private static final long UID = 6948989635489677685L;
	    private String studentName;
	    private Teacher teacher;

	    public StudentSh(String studentName, Teacher teacher) {
	        this.studentName = studentName;
	        this.teacher = teacher;
	    }

	    public Object deepClone() {
	        try {
	            //将对象写到流里
	            ByteArrayOutputStream bo = new ByteArrayOutputStream();
	            ObjectOutputStream oo = new ObjectOutputStream(bo);
	            oo.writeObject(this);
	            //从流里读出来
	            ByteArrayInputStream bi = new ByteArrayInputStream(bo.toByteArray());
	            ObjectInputStream oi = new ObjectInputStream(bi);
	            return (oi.readObject());
	        } catch (Exception e) {
	            return null;
	        }
	    }

	}

	public class Client {
	    public static void main(String[] args) throws Exception {
	        Teacher teacher = new Teacher("snail");

	        StudentSh student1  =new StudentSh("wjk",teacher);
	        StudentSh student2 = (StudentSh) student1.deepClone();
	        student2.getTeacher().setName("snail改变");
	        System.out.println(student1.getTeacher().getName());
	        System.out.println(student2.getTeacher().getName());
	     }
	}
	**运行结果**
	snail
	snail改变