我有一些使用 Object.clone 执行深层复制的代码,但我正在尝试使用更“可接受”的复制构造函数技术来重写它。下面是我正在尝试做的两个简单示例,第一个使用克隆,第二个使用复制构造函数。
使用克隆的深拷贝
import java.util.*;
abstract class Person implements Cloneable {
String name;
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
class Teacher extends Person implements Cloneable {
int courses;
public String toString() { return name + ": courses=" + courses; }
}
class Student extends Person implements Cloneable {
double gpa;
public String toString() { return name + ": gpa=" + gpa; }
}
public class DeepCopy_Clone {
private static List<Person> deepCopy(List<Person> people) throws CloneNotSupportedException {
List<Person> copy = new ArrayList<Person>();
for (Person person : people) {
copy.add((Person)person.clone());
}
return copy;
}
public static void main(String[] args) throws CloneNotSupportedException {
ArrayList<Person> people = new ArrayList<Person>();
Teacher teacher = new Teacher();
teacher.name = "Teacher";
teacher.courses = 5;
people.add(teacher);
Student student = new Student();
student.name = "Student";
student.gpa = 4.0;
people.add(student);
List<Person> peopleCopy = deepCopy(people);
// Invalidate the original data to prove a deep copy occurred
teacher.name = null;
teacher.courses = -1;
student.name = null;
student.gpa = -1;
for (Person person : peopleCopy) {
System.out.println(person.toString());
}
}
}
使用复制构造函数的深拷贝
import java.util.*;
abstract class Person {
String name;
public Person() {}
public Person(Person other) {
this.name = other.name;
}
public Person deepCopy() {
if (this instanceof Teacher) {
return new Teacher((Teacher)this);
} else if (this instanceof Student) {
return new Student((Student)this);
}
throw new Error("Unknown type of person");
}
}
class Teacher extends Person {
int courses;
public Teacher() {}
public Teacher(Teacher other) {
super(other);
this.courses = other.courses;
}
public String toString() { return name + ": courses=" + courses; }
}
class Student extends Person {
double gpa;
public Student() {}
public Student(Student other) {
super(other);
this.gpa = other.gpa;
}
public String toString() { return name + ": gpa=" + gpa; }
}
public class DeepCopy_ConstructorAlternative {
private static List<Person> deepCopy(List<Person> people) {
List<Person> copy = new ArrayList<Person>();
for (Person person : people) {
copy.add(person.deepCopy());
}
return copy;
}
public static void main(String[] args) {
ArrayList<Person> people = new ArrayList<Person>();
Teacher teacher = new Teacher();
teacher.name = "Teacher";
teacher.courses = 5;
people.add(teacher);
Student student = new Student();
student.name = "Student";
student.gpa = 4.0;
people.add(student);
List<Person> peopleCopy = deepCopy(people);
// Invalidate the original data to prove a deep copy occurred
teacher.name = null;
teacher.courses = -1;
student.name = null;
student.gpa = -1;
for (Person person : peopleCopy) {
System.out.println(person.toString());
}
}
}
我发现有趣的是,尽管大家都在谈论 Java 中克隆的弊端,但克隆替代方案需要更少的代码和更少的强制转换(至少在这种特殊情况下)。
我很感激有关复制构造函数替代方案的反馈。你会做不同的事情吗?谢谢。