JAVA 自定义比较器

参考链接：https://blog.csdn.net/whing123/article/details/77851737

 Comparable 

需要类实现Comparable接口，重写compareTo方法

Comparator

Comparator接口一般不会被集合元素类所实现，而是单独实现或者匿名内部类方式实现

重写compare()方法

 Comparable 

import java.util.*;

public class RongQi {
    public static void main(String[] args) {
      
        Student s1 = new Student("Allen", 20, 1);
        Student s2 = new Student("Allen", 20, 45);
        Student s3 = new Student("Catalina", 40, 2);
        Student s4 = new Student("Diana", 30, 0);
        List<Student> l = new LinkedList();
        l.add(s3);
        l.add(s1);
        l.add(s4);
        l.add(s2);
        Collections.sort(l);//对list排序
        Iterator<Student> it = l.iterator();
        while (it.hasNext()) {
            System.out.println(it.next());
        }

    }

    static class Student implements Comparable<Student> {
        // public class Student{
        private String name;
        private int age;
        private int id;

        // public Student() {
        // }

        public Student(String name, int age, int id) {
            this.name = name;
            this.age = age;
            this.id = id;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public int getAge() {
            return age;
        }

        public void setAge(int age) {
            this.age = age;
        }

        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }

        @Override
        public String toString() {
            return "Student{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    ", id=" + id +
                    '}';
        }

        @Override
        public int compareTo(Student s1) {

            int cmp = name.compareTo(s1.name);// 继续加入ID
            if (cmp != 0) {
                return cmp;
            } else {
                int cmp1 = age - s1.age;
                if (cmp1 != 0) {
                    return cmp1;
                } else {
                    return id - s1.id;
                }
            }

        }
    }

}

Student{name='Allen', age=20, id=1}
Student{name='Allen', age=20, id=45}
Student{name='Catalina', age=40, id=2}
Student{name='Diana', age=30, id=0}

 我一般用 Comparator

import java.util.*;

public class Main {
    public static void main(String[] args) {

        Student s1 = new Student("Allen", 20, 1);
        Student s2 = new Student("Allen", 20, 45);
        Student s3 = new Student("Catalina", 40, 2);
        Student s4 = new Student("Diana", 30, 0);
        List<Student> l = new LinkedList();
        l.add(s3);
        l.add(s1);
        l.add(s4);
        l.add(s2);
        Collections.sort(l, new StudentComparator());// 对list排序
        Iterator<Student> it = l.iterator();
        while (it.hasNext()) {
            System.out.println(it.next());
        }

    }

    static class Student {
        // public class Student{
        private String name;
        private int age;
        private int id;

        public Student(String name, int age, int id) {
            this.name = name;
            this.age = age;
            this.id = id;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public int getAge() {
            return age;
        }

        public void setAge(int age) {
            this.age = age;
        }

        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }

        @Override
        public String toString() {
            return "Student{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    ", id=" + id +
                    '}';
        }

    }

    static class StudentComparator implements Comparator {

        public int compare(Object o1, Object o2) {
            Student s1 = (Student) o1;
            Student s2 = (Student) o2;
            int cmp = s1.name.compareTo(s2.name);// 继续加入ID
            if (cmp != 0) {
                return cmp;
            } else {
                int cmp1 = s1.age - s2.age;
                if (cmp1 != 0) {
                    return cmp1;
                } else {
                    return s1.id - s2.id;
                }
            }
        }
    }

}

Student{name='Allen', age=20, id=1}
Student{name='Allen', age=20, id=45}
Student{name='Catalina', age=40, id=2}
Student{name='Diana', age=30, id=0}

自定义数组排序

class Solution {
     static class StringComparator implements Comparator<String> {
        @Override
        public int compare(String s1, String s2) {
            //操作
            return s1.compareTo(s2);
        }

    }
    public String minNumber(int[] nums) {
        String[] str = new String[nums.length];
        String s ="";
        for (int i = 0; i < nums.length; i++) {
            str[i] = Integer.toString(nums[i]);
        }
        Arrays.sort(str, new StringComparator());
        for(String ss:str){
            s+=ss;
        }
        return s;
    }
}