1、比较器
①比较器的引入
a.首先，当我们单一地比较某一种数据类型的数组时，可以直接用Arrays.sort()进行实现
b.而当我们同时含有多个参数时，并没有告诉我们按照什么来进行排序，此时，若是用Arrays.sort()就会出现报错的情况
基于这种情况，我们了解到，若是要将自定义类型进行大小比较 ，就要引入能够实现比较的接口，下面我们介绍Comparable和Comparator这两种比较器
1.1Comparable接口
①实现Comparable接口的操作
②通过Comparable接口实现年龄的排序
③通过Comparable来实现名字的排序（注意名字是引用类，比较时应该是用compareTo（）来进行）
④升序降序
由于最终是利用的Arrays.sort()进行的比较，该方法底层是升序的操作，若是想转换为降序，只需要将重写的compareTo()方法中两项互换位置即可
变为降序后代码运行结果：
⑤缺点！！！
Comparable对类的倾入性很强。由上面我们可知，要想比较新的类型就要更改compareTo（）中的类型重新进行比较，这个在以后的工作中极大可能会使整个代码出现逻辑问题，可读性问题，因此我们引入下一类很灵活，倾入性不强的Comparator接口
⑥整体代码如下：
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,"张三",98.0);
Student student2=new Student(18,"李四",97.9);
//if(student1.compareTo(student2)>0)返回1；根据下面的方法进行进一步的返回
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
//谁调用这个方法，谁就是this
public int compareTo(Student o) {
//return this.age-o.age;
return o.name.compareTo(this.name);
}
}1.2Comparator接口
①实现Comparable接口的操作：
②通过该接口实现的姓名的比较：
③升序降序
执行后的结果：
④优点
灵活，对类的倾入性不强
⑤整体代码如下：
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);
//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);//默认是从小到大的排序
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如何实现Cloneable接口：
Object 类中存在一个 clone 方法, 调用这个方法可以创建一个对象的 "拷贝". 但是要想合法调用 clone 方法, 必须要先实现 Clonable 接口, 否则就会抛出 CloneNotSupportedException 异常。
a.实现Cloneable接口
b.重写Cloneable方法
c.抛异常，强制类型转换
②面试中常问问题：
你知道Cloneable接口吗？为什么它是一个空接口，它有什么作用呢？
空接口，标志接口，代表这个类是可以被克隆的
③克隆的原理图：
④整体代码的实现：
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深拷贝和浅拷贝
①深浅拷贝：
决定是深拷贝还是浅拷贝，并不是方法的用途，而是代码的实现
②浅拷贝示例
浅拷贝代码如下：
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深拷贝示例：（将tmp中的money也进行拷贝）
深拷贝代码如下:
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);
}
}总结
本篇文章就到这里了，希望能够给你带来帮助，也希望您能够多多关注编程网的更多内容!
