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Java的Comparable,Comparator和Cloneable三大接口詳解

更新時(shí)間：2022年03月14日 15:29:23 作者：反內(nèi)碼者

這篇文章主要為大家詳細(xì)介紹了Java的Comparable,Comparator和Cloneable的接口，文中示例代碼介紹的非常詳細(xì)，具有一定的參考價(jià)值，感興趣的小伙伴們可以參考一下，希望能夠給你帶來幫助

1、比較器

①比較器的引入

a.首先，當(dāng)我們單一地比較某一種數(shù)據(jù)類型的數(shù)組時(shí)，可以直接用Arrays.sort()進(jìn)行實(shí)現(xiàn)

b.而當(dāng)我們同時(shí)含有多個(gè)參數(shù)時(shí)，并沒有告訴我們按照什么來進(jìn)行排序，此時(shí)，若是用Arrays.sort()就會(huì)出現(xiàn)報(bào)錯(cuò)的情況

基于這種情況，我們了解到，若是要將自定義類型進(jìn)行大小比較，就要引入能夠?qū)崿F(xiàn)比較的接口，下面我們介紹Comparable和Comparator這兩種比較器

1.1Comparable接口

①實(shí)現(xiàn)Comparable接口的操作

②通過Comparable接口實(shí)現(xiàn)年齡的排序

③通過Comparable來實(shí)現(xiàn)名字的排序（注意名字是引用類，比較時(shí)應(yīng)該是用compareTo（）來進(jìn)行）

④升序降序

由于最終是利用的Arrays.sort()進(jìn)行的比較，該方法底層是升序的操作，若是想轉(zhuǎn)換為降序，只需要將重寫的compareTo()方法中兩項(xiàng)互換位置即可

變?yōu)榻敌蚝蟠a運(yùn)行結(jié)果：

⑤缺點(diǎn)?。?！

Comparable對(duì)類的傾入性很強(qiáng)。由上面我們可知，要想比較新的類型就要更改compareTo（）中的類型重新進(jìn)行比較，這個(gè)在以后的工作中極大可能會(huì)使整個(gè)代碼出現(xiàn)邏輯問題，可讀性問題，因此我們引入下一類很靈活，傾入性不強(qiáng)的Comparator接口

⑥整體代碼如下：

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 +
                 '}';
     }
    public static void main3(String[] args) {
        Student student1=new Student(12,"張三",98.0);
        Student student2=new Student(18,"李四",97.9);
        //if(student1.compareTo(student2)>0)返回1；根據(jù)下面的方法進(jìn)行進(jìn)一步的返回
        System.out.println(student1.compareTo(student2));
    }
    public static void main(String[] args) {
        Student []student=new Student[3];
        student[0]=new Student(36,"zhangsan",98.0);
        student[1]=new Student(18,"lisi",97.9);
        student[2]=new Student(27,"wangwu",65.3);
        System.out.println(Arrays.toString(student));
        Arrays.sort(student);
        System.out.println(Arrays.toString(student));
    }
     public static void main1(String[] args) {
         int []array=new int []{2,5,3,6,8};
         System.out.println(Arrays.toString(array));
         Arrays.sort(array);
         System.out.println(Arrays.toString(array));
     }
    @Override
//誰調(diào)用這個(gè)方法，誰就是this
    public int compareTo(Student o) {
    //return this.age-o.age;
    return o.name.compareTo(this.name);
    }
}

1.2Comparator接口

①實(shí)現(xiàn)Comparable接口的操作：

②通過該接口實(shí)現(xiàn)的姓名的比較：

③升序降序

執(zhí)行后的結(jié)果：

④優(yōu)點(diǎn)

靈活，對(duì)類的傾入性不強(qiáng)

⑤整體代碼如下：

import java.util.Arrays;
import java.util.Comparator;
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 +
                '}';
    }
}
class AgeComparator implements Comparator<Student> {
    @Override
    public int compare(Student o1, Student o2) {
        return o1.age-o2.age;
    }
}
class ScoreComparator implements Comparator<Student> {
    @Override
    public int compare(Student o1, Student o2) {
        return (int)(o1.score-o2.score);
    }
}
class NameComparator implements Comparator<Student> {
    @Override
    public int compare(Student o1, Student o2) {
        return o1.name.compareTo(o2.name);
    }
}
public class Test {
    public static void main2(String[] args) {
        Student students1 = new Student(1,"bit",98.9);
        Student students2 = new Student(2,"abc",88.9);
       /* if(students1.compareTo( students2) > 0) {
        }*/
        //System.out.println(students1.compareTo( students2));
        AgeComparator ageComparator = new AgeComparator();
        System.out.println(ageComparator.compare(students1,students2));
    }
    public static void main(String[] args) {
        Student[] student = new Student[3];
        student[0] = new Student(12,"lisi",98.9);
        student[1] = new Student(6,"zangwu",88.9);
        student[2] = new Student(18,"whangsan",18.9);
        System.out.println(Arrays.toString(student));
        AgeComparator ageComparator = new AgeComparator();
        ScoreComparator scoreComparator = new ScoreComparator();
        NameComparator nameComparator = new NameComparator();
        Arrays.sort(student,nameComparator);//默認(rèn)是從小到大的排序
        System.out.println(Arrays.toString(student));
    }
    public static void main1(String[] args) {
        int[] array = {1,21,3,14,5,16};
        System.out.println(Arrays.toString(array));
        Arrays.sort(array);
        System.out.println(Arrays.toString(array));
    }
}

2、Cloneable接口

①如何實(shí)現(xiàn)Cloneable接口：

Object 類中存在一個(gè) clone 方法, 調(diào)用這個(gè)方法可以創(chuàng)建一個(gè)對(duì)象的 "拷貝". 但是要想合法調(diào)用 clone 方法, 必須要先實(shí)現(xiàn) Clonable 接口, 否則就會(huì)拋出 CloneNotSupportedException 異常。

a.實(shí)現(xiàn)Cloneable接口

b.重寫Cloneable方法

c.拋異常，強(qiáng)制類型轉(zhuǎn)換

②面試中常問問題：

你知道Cloneable接口嗎？為什么它是一個(gè)空接口，它有什么作用呢？

空接口，標(biāo)志接口，代表這個(gè)類是可以被克隆的

③克隆的原理圖：

④整體代碼的實(shí)現(xiàn)：

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 TestDemo {
    public static void main(String[] args) throws CloneNotSupportedException {
        Person person = new Person();
        person.age=13;
        Person person2=(Person)person.clone();
        System.out.println(person2);
        System.out.println(person);
        System.out.println("===========");
        person2.age=14;
        System.out.println(person);
        System.out.println(person2);
    }
}

2.1深拷貝和淺拷貝

①深淺拷貝：

決定是深拷貝還是淺拷貝，并不是方法的用途，而是代碼的實(shí)現(xiàn)

②淺拷貝示例

淺拷貝代碼如下：

class Money implements Cloneable{
    public double m = 12.5;
}
class Person implements Cloneable{
    public int age;
    public Money money = new Money();
    public void eat() {
        System.out.println("吃！");
    }
    @Override
    public String toString() {
        return "Person{" +
                "age=" + age +
                '}';
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        Person tmp = (Person)super.clone();
        return tmp;
    }
}
public class TestDemo {
    public static void main(String[] args) throws CloneNotSupportedException {
        Person person = new Person();
        Person person2 = (Person)person.clone();
        System.out.println(person.money.m);
        System.out.println(person2.money.m);
        System.out.println("=====================");
        person2.money.m = 98.5;
        System.out.println(person.money.m);
        System.out.println(person2.money.m);
    }
}

③深拷貝示例：（將tmp中的money也進(jìn)行拷貝）

深拷貝代碼如下:

class Money implements Cloneable{
    public double m = 12.5;
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}
class Person implements Cloneable{
    public int age;
    public Money money = new Money();
    public void eat() {
        System.out.println("吃！");
    }
    @Override
    public String toString() {
        return "Person{" +
                "age=" + age +
                '}';
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        Person tmp = (Person)super.clone();
        tmp.money = (Money) this.money.clone();
        return tmp;
        //return super.clone();
    }
}
public class TestDemo {
    public static void main(String[] args) throws CloneNotSupportedException {
        Person person = new Person();
        Person person2 = (Person)person.clone();
        System.out.println(person.money.m);
        System.out.println(person2.money.m);
        System.out.println("=====================");
        person2.money.m = 98.5;
        System.out.println(person.money.m);
        System.out.println(person2.money.m);
    }
}