扬州网站商城建设价格,信息免费发布平台,南宁建站免费模板,网站做框架文章目录1.拷贝的引入1.1引用拷贝1.2对象拷贝2.深拷贝与浅拷贝2.1浅拷贝2.2深拷贝1.拷贝的引入
1.1引用拷贝
创建一个指向对象的引用变量的拷贝
Teacher teacher new Teacher(Taylor,26);
Teacher otherteacher teacher;
System.out.println(teacher);
System…
文章目录1.拷贝的引入1.1引用拷贝1.2对象拷贝2.深拷贝与浅拷贝2.1浅拷贝2.2深拷贝1.拷贝的引入
1.1引用拷贝
创建一个指向对象的引用变量的拷贝
Teacher teacher new Teacher(Taylor,26);
Teacher otherteacher teacher;
System.out.println(teacher);
System.out.println(otherteacher);
输出
blog.Teacher355da254
blog.Teacher355da254由输出结果可以看出它们的地址值是相同的那么它们肯定是同一个对象。teacher和otherteacher的只是引用而已他们都指向了一个相同的对象Teacher(“Taylor”,26)。 这就叫做引用拷贝。
1.2对象拷贝
创建对象本身的一个副本。
Teacher teacher new Teacher(Swift,26);
Teacher otherteacher (Teacher)teacher.clone();
System.out.println(teacher);
System.out.println(otherteacher);
输出
blog.Teacher355da254
blog.Teacher4dc63996
由输出结果可以看出它们的地址是不同的也就是说创建了新的对象 而不是把原对象的地址赋给了一个新的引用变量,这就叫做对象拷贝。
2.深拷贝与浅拷贝
在Java语言里当我们需要拷贝一个对象时有两种类型的拷贝浅拷贝与深拷贝。 浅拷贝只是拷贝了源对象的地址所以源对象的值发生变化时拷贝对象的值也会发生变化。 而深拷贝则是拷贝了源对象的所有值所以即使源对象的值发生变化时拷贝对象的值也不会改变。如下图描述
2.1浅拷贝
定义 被复制对象的所有变量都含有与原来的对象相同的值而所有的对其他对象的引用仍然指向原来的对象。即对象的浅拷贝会对“主”对象进行拷贝但不会复制主对象里面的对象。里面的对象“会在原来的对象和它的副本之间共享。
简而言之浅拷贝仅仅复制所考虑的对象而不复制它所引用的对象
浅拷贝实例
public class ShallowCopy {public static void main(String[] args) throws CloneNotSupportedException {Teacher teacher new Teacher();teacher.setName(Delacey);teacher.setAge(29);Student2 student1 new Student2();student1.setName(Dream);student1.setAge(18);student1.setTeacher(teacher);Student2 student2 (Student2) student1.clone();//拷贝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(修改老师的信息后-------------);// 修改老师的信息teacher.setName(Jam);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;}Overridepublic Object clone() throws CloneNotSupportedException {Object object super.clone();return object;}}
输出
拷贝后
Dream
18
Delacey
29
修改老师的信息后-------------
Jam
Jam结果分析 两个引用student1和student2指向不同的两个对象但是两个引用student1和student2中的两个teacher引用指向的是同一个对象所以说明是浅拷贝。
2.2深拷贝
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。当对象和它所引用的对象一起拷贝时即发生深拷贝。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引用的对象都复制了一遍。
实现深拷贝 实例1
public class DeepCopy {public static void main(String[] args) throws Exception {Teacher2 teacher new Teacher2();teacher.setName(Delacey);teacher.setAge(29);Student3 student1 new Student3();student1.setName(Dream);student1.setAge(18);student1.setTeacher(teacher);Student3 student2 (Student3) student1.clone();//拷贝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(修改老师的信息后-------------);// 修改老师的信息teacher.setName(Jam);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;}Overridepublic 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;}Overridepublic Object clone() throws CloneNotSupportedException {// 浅复制时// Object object super.clone();// return object;// 改为深复制Student3 student (Student3) super.clone();// 本来是浅复制现在将Teacher对象复制一份并重新set进来student.setTeacher((Teacher2) student.getTeacher().clone());return student;}}
输出结果
拷贝后
Dream
18
Delacey
29
修改老师的信息后-------------
Jam
Delacey
结果分析 两个引用student1和student2指向不同的两个对象两个引用student1和student2中的两个teacher引用指向的是两个对象但对teacher对象的修改只能影响student1对象,所以说是深拷贝。
下图为 teacher姓名Delacey更改前 下图为 teacher姓名Jam更改后 利用序列化实现深拷贝
public class DeepCopyServiable {public static void main(String[] args) throws Exception {Teacher3 t new Teacher3();t.setName(Taylor);t.setAge(28);Student3 s1 new Student3();s1.setAge(20);s1.setName(blank space);s1.setTeacher(t);Student3 s2 (Student3) s1.deepClone();//拷贝System.out.println(拷贝后:);System.out.println(s2.getName());System.out.println(s2.getAge());System.out.println(s2.getTeacher().getName());System.out.println(s2.getTeacher().getAge());System.out.println(---------------------------);t.setName(swift);System.out.println(修改后);System.out.println(s1.getTeacher().getName());System.out.println(s2.getTeacher().getName());}
}class Teacher3 implements Serializable {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 Student3 implements Serializable {private String name;private int age;private Teacher3 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 Teacher3 getTeacher() {return teacher;}public void setTeacher(Teacher3 teacher) {this.teacher teacher;}public Object deepClone() throws Exception {// 序列化ByteArrayOutputStream bos new ByteArrayOutputStream();ObjectOutputStream oos new ObjectOutputStream(bos);oos.writeObject(this);// 反序列化ByteArrayInputStream bis new ByteArrayInputStream(bos.toByteArray());ObjectInputStream ois new ObjectInputStream(bis);return ois.readObject();}
}输出结果
拷贝后:
blank space
20
Taylor
28
---------------------------
修改后
swift
Taylor
结果分析说明用序列化的方式实现了对象的深拷贝
参考博文侵删 https://blog.csdn.net/baiye_xing/article/details/71788741 https://www.cnblogs.com/ysocean/p/8482979.html https://www.cnblogs.com/xinruyi/p/11537963.html
