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一、拷贝的引入
(1)、援用拷贝
创立一个指向对象的援用变量的拷贝。
Teacher teacher = new Teacher("Taylor",26);
Teacher otherteacher = teacher;
System.out.println(teacher);
System.out.println(otherteacher);
输入后果:
blog.Teacher@355da254
blog.Teacher@355da254
后果剖析:由输入后果能够看出,它们的地址值是雷同的,那么它们必定是同一个对象。teacher 和 otherteacher 的只是援用而已,他们都指向了一个雷同的对象 Teacher(“Taylor”,26)。这就叫做援用拷贝。
(2)、对象拷贝
创建对象自身的一个正本。
Teacher teacher = new Teacher("Swift",26);
Teacher otherteacher = (Teacher)teacher.clone();
System.out.println(teacher);
System.out.println(otherteacher);
输入后果:
blog.Teacher@355da254
blog.Teacher@4dc63996
后果剖析:由输入后果能够看出,它们的地址是不同的,也就是说创立了新的对象,而不是把原对象的地址赋给了一个新的援用变量, 这就叫做对象拷贝。
注:深拷贝和浅拷贝都是对象拷贝
二、浅拷贝
(1)、定义
被复制对象的所有变量都含有与原来的对象雷同的值,而所有的对其余对象的援用依然指向原来的对象。即对象的浅拷贝会对“主”对象进行拷贝,但不会复制主对象外面的对象。”外面的对象“会在原来的对象和它的正本之间共享。
简而言之,浅拷贝仅仅复制所思考的对象,而不复制它所援用的对象
(2)、浅拷贝实例
package com.test;
public class ShallowCopy {public static void main(String[] args) throws CloneNotSupportedException {Teacher teacher = new Teacher();
teacher.setName("riemann");
teacher.setAge(27);
Student2 student1 = new Student2();
student1.setName("edgar");
student1.setAge(18);
student1.setTeacher(teacher);
Student2 student2 = (Student2) student1.clone();
System.out.println("拷贝后");
System.out.println(student2.getName());
System.out.println(student2.getAge());
System.out.println(student2.getTeacher().getName());
System.out.println(student2.getTeacher().getAge());
System.out.println("批改老师的信息后 -------------");
// 批改老师的信息
teacher.setName("Games");
System.out.println(student1.getTeacher().getName());
System.out.println(student2.getTeacher().getName());
}
}
class Teacher implements Cloneable {
private String name;
private int age;
public String getName() {return name;}
public void setName(String name) {this.name = name;}
public int getAge() {return age;}
public void setAge(int age) {this.age = age;}
}
class Student2 implements Cloneable {
private String name;
private int age;
private Teacher teacher;
public String getName() {return name;}
public void setName(String name) {this.name = name;}
public int getAge() {return age;}
public void setAge(int age) {this.age = age;}
public Teacher getTeacher() {return teacher;}
public void setTeacher(Teacher teacher) {this.teacher = teacher;}
public Object clone() throws CloneNotSupportedException {Object object = super.clone();
return object;
}
}
输入后果:
拷贝后
edgar
18
riemann
27
批改老师的信息后 -------------
Games
Games
后果剖析:两个援用 student1 和 student2 指向不同的两个对象,然而两个援用 student1 和 student2 中的两个 teacher 援用指向的是同一个对象,所以阐明是浅拷贝。
三、深拷贝
(1)、定义
深拷贝是一个整个独立的对象拷贝,深拷贝会拷贝所有的属性, 并拷贝属性指向的动态分配的内存。当对象和它所援用的对象一起拷贝时即产生深拷贝。深拷贝相比于浅拷贝速度较慢并且花销较大。
简而言之,深拷贝把要复制的对象所援用的对象都复制了一遍。
(2)、深拷贝实例
package com.test;
public class DeepCopy {public static void main(String[] args) throws CloneNotSupportedException {Teacher2 teacher = new Teacher2();
teacher.setName("riemann");
teacher.setAge(27);
Student3 student1 = new Student3();
student1.setName("edgar");
student1.setAge(18);
student1.setTeacher(teacher);
Student3 student2 = (Student3) student1.clone();
System.out.println("拷贝后");
System.out.println(student2.getName());
System.out.println(student2.getAge());
System.out.println(student2.getTeacher().getName());
System.out.println(student2.getTeacher().getAge());
System.out.println("批改老师的信息后 -------------");
// 批改老师的信息
teacher.setName("Games");
System.out.println(student1.getTeacher().getName());
System.out.println(student2.getTeacher().getName());
}
}
class Teacher2 implements Cloneable {
private String name;
private int age;
public String getName() {return name;}
public void setName(String name) {this.name = name;}
public int getAge() {return age;}
public void setAge(int age) {this.age = age;}
public Object clone() throws CloneNotSupportedException {return super.clone();
}
}
class Student3 implements Cloneable {
private String name;
private int age;
private Teacher2 teacher;
public String getName() {return name;}
public void setName(String name) {this.name = name;}
public int getAge() {return age;}
public void setAge(int age) {this.age = age;}
public Teacher2 getTeacher() {return teacher;}
public void setTeacher(Teacher2 teacher) {this.teacher = teacher;}
public Object clone() throws CloneNotSupportedException {
// 浅复制时:// Object object = super.clone();
// return object;
// 改为深复制:Student3 student = (Student3) super.clone();
// 原本是浅复制,当初将 Teacher 对象复制一份并从新 set 进来
student.setTeacher((Teacher2) student.getTeacher().clone());
return student;
}
}
输入后果:
拷贝后
edgar
18
riemann
27
批改老师的信息后 -------------
Games
riemann
后果剖析:
两个援用 student1 和 student2 指向不同的两个对象,两个援用 student1 和 student2 中的两个 teacher 援用指向的是两个对象,但对 teacher 对象的批改只能影响 student1 对象, 所以说是深拷贝。
对于 Java 深拷贝和浅拷贝区别,你学废了么?