这篇文章主要为大家分析了 Java SE面向对象编程的3个常用接口分别是什么的相关知识点，内容详细易懂，操作细节合理，具有一定参考价值。如果感兴趣的话，不妨跟着跟随小编一起来看看，下面跟着小编一起深入学习“ Java SE面向对象编程的3个常用接口分别是什么”的知识吧。
1.Comparable
前言,想要排序Student.有代码:
import java.util.Arrays; class Student { public int age; public String name; public double score; public Student(int age, String name, double score) { this.age = age; this.name = name; this.score = score; } @Override public String toString() { return "Student{" + "age=" + age + ", name='" + name + '\'' + ", score=" + score + '}'; }} public class TestDemo { public static void main(String[] args) { Student[] students = new Student[3]; students[0] = new Student(12,"niubi",99.9); students[1] = new Student(20,"liuren",18.9); students[2] = new Student(80,"laoren",50.9); System.out.println(Arrays.toString(students)); Arrays.sort(students); System.out.println(Arrays.toString(students)); }}此代码运行报错:
原因: 没有告诉要如何进行排序,是年龄还是姓名还是分数.没有告诉比较的规则
解决方式:
如果自定义的数据类型 进行大小比较 一定要实现可以比较的接口
import java.util.Arrays; class Student implements Comparable<Student>{ public int age; public String name; public double score; public Student(int age, String name, double score) { this.age = age; this.name = name; this.score = score; } @Override public String toString() { return "Student{" + "age=" + age + ", name='" + name + '\'' + ", score=" + score + '}'; } //谁调用这个方法 谁就是this @Override public int compareTo(Student o) { //return this.age - o.age;//从小到大 return o.age - this.age;//从大到小 } } public class TestDemo { public static void main(String[] args) { Student[] students = new Student[3]; students[0] = new Student(12,"niubi",99.9); students[1] = new Student(6,"liuren",18.9); students[2] = new Student(80,"laoren",50.9); System.out.println("比较前 "+Arrays.toString(students)); Arrays.sort(students);//默认从小到大排序 System.out.println("比较后 "+Arrays.toString(students)); }}如果要 分数比较 和 姓名比较
//谁调用这个方法 谁就是this @Override public int compareTo(Student o) { //return this.age - o.age;//从小到大 //return o.age - this.age;//从大到小 return (int) (this.score - o.score);//分数排序 return this.name.compareTo(o.name);//姓名排序 }缺点: 这个接口对类的侵入性非常强.一旦写好了,不敢轻易改动.
如何降低对类的侵入性呢?
使用Comparator
2.Comparator 比较器
import java.util.Arrays;import java.util.Comparator; class Student1 { public int age; public String name; public double score; public Student1(int age, String name, double score) { this.age = age; this.name = name; this.score = score; } @Override public String toString() { return "Student{" + "age=" + age + ", name='" + name + '\'' + ", score=" + score + '}'; }} class AgeComparator implements Comparator<Student1>{ @Override public int compare(Student1 o1, Student1 o2) { return o1.age - o2.age; }} class ScoreComparator implements Comparator<Student1>{ @Override public int compare(Student1 o1, Student1 o2) { return (int) (o1.score - o2.score); }} class NameComparator implements Comparator<Student1>{ @Override public int compare(Student1 o1, Student1 o2) { return o1.name.compareTo(o2.name); }} public class TestDemo1 { public static void main(String[] args) { Student1[] students1 = new Student1[3]; students1[0] = new Student1(12,"niubi",99.9); students1[1] = new Student1(6,"liuren",18.9); students1[2] = new Student1(80,"laoren",50.9); System.out.println("比较前 "+Arrays.toString(students1)); AgeComparator ageComparator = new AgeComparator(); Arrays.sort(students1,ageComparator); System.out.println("比较后(按年龄) "+Arrays.toString(students1)); ScoreComparator scoreComparator = new ScoreComparator(); Arrays.sort(students1,scoreComparator); System.out.println("比较后(按姓名) "+Arrays.toString(students1)); NameComparator nameComparator = new NameComparator(); Arrays.sort(students1,nameComparator); System.out.println("比较后(按分数) "+Arrays.toString(students1)); }}运行结果:
优点:对类的侵入性非常弱.
3.Cloneable
面试问题:
你知道Cloneable接口吗?为啥这个接口是一个空接口?有啥作用?
空接口 -> 标志接口 -> 代表当前这个类是可以被克隆的.
class Person implements Cloneable{ public int age ; public void eat(){ System.out.println("吃!"); } @Override public String toString() { return "Person{" + "age=" + age + '}'; } @Override protected Object clone() throws CloneNotSupportedException { return super.clone(); }}public class TestDemo2 { public static void main(String[] args) throws CloneNotSupportedException { Person person = new Person(); person.age = 99; Person person2 = (Person) person.clone(); System.out.println(person.age); System.out.println(person2.age); System.out.println("=========="); person2.age = 199; System.out.println(person.age); System.out.println(person2.age); }}运行结果:
注意事项:
引用的对象要想被克隆,必须实现Cloneable接口.
必须重写克隆方法,并且声明异常.
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