Comparable和Comparator的区别和用法

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星辰大数据 2022-03-29 14:28:33 博主文章分类：Java基础 ©著作权

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Comparable和Comparator的区别和用法

1、代码

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.function.Consumer;
/**
 * 1、Comparable和Comparator的用法
 * 2、引用类型数组的排序和遍历 排序： Arrays.sort()            遍历：Arrays.Stream().forEach()
 * 3、引用类型集合的排序和遍历 排序：Collections.sort() list.sort()  遍历：list.forEach()
 * 4、Lambda表达式的使用
 * @author com
 *
 */
class Students implements Comparable<Students>{
  private int id;
  private String name;
  private int age;  //年龄
  private int score;  //分数
  Students(int id,String name,int age,int score){
    this.id = id;
    this.name = name;
    this.age = age;
    this.score = score;
  }
  public int getId() {
    return id;
  }
  public int getAge() {
    return age;
  }
  public int getScore() {
    return score;
  }
  @Override
  public String toString() {
    return id+","+name+","+age+","+score;
  }
  @Override
  public int compareTo(Students s) {
    return this.id - s.id;  //按id升序
  }
}
class StudentsComparator implements Comparator<Students>{
  @Override
  public int compare(Students s1,Students s2) {
    return s1.getScore() - s2.getScore();
  }
}
public class CompareTest {
  
  public static void main(String[] args) {
    Students s1 = new Students(1, "小白", 25, 99);
    Students s2 = new Students(2, "小黑", 22, 100);
    Students s3 = new Students(9, "小黄", 20, 98);
    Students s4 = new Students(4, "小蓝", 21, 97);
    Students s5 = new Students(5, "小红", 20, 95);
    Students[] stu = {s1,s2,s3,s4,s5};
    System.out.println("-----------------实现comparable接口-------------按id升序---------------------------------------");
    Arrays.sort(stu);
    Arrays.stream(stu).forEach(new Consumer<Students>() {
      @Override
      public void accept(Students s) {
        System.out.println(s);
      }
    });
    System.out.println("-----------------实现comparable接口-----匿名内部类重写------------按id降序--------------");
    Arrays.sort(stu, new Comparator<Students>() {
      @Override
      public int compare(Students s1, Students s2) {
        return s2.getId() - s1.getId();
      }
    });
    Arrays.stream(stu).forEach(System.out::println);
    System.out.println("-----------------实现comparable接口-------lambda表达式重写-------按年龄升序--------------");
    Arrays.sort(stu,(t1,t2)->{return t1.getAge()-t2.getAge();});
    Arrays.stream(stu).forEach(System.out::println);
    System.out.println("-----------------实现comparable接口-------lambda表达式重写-------按成绩升序--------------");
    Comparator<Students> comparator = new StudentsComparator();
    Arrays.sort(stu,comparator);
    Arrays.stream(stu).forEach(System.out::println);
    System.out.println("-----用ArraysList实现-----Collections.sort()方法调用的是默认(Comparable)的排序方法----按id升序-----------------");
    List<Students> list = new ArrayList<>();
    Collections.addAll(list, s1,s2,s3,s4,s5);
    Collections.sort(list); //Collections.sort调用的是默认的排序方法
    list.forEach((s)->{System.out.println(s);});
    System.out.println("-----用List实现-----ArraysList.sort()方法以匿名内部类的形式实现Comparator接口的重写--------");
//    list.sort(comparator);  //List.sort()方法调用Comparator实现类接口
    list.sort(new Comparator<Students>() {
      @Override
      public int compare(Students t1,Students t2) {
        return t2.getScore() - t1.getScore();
      }
    });
    list.forEach(new Consumer<Students>() {
      @Override
      public void accept(Students s) {
        System.out.println(s);
      }
    });
    
  }
}