java 自定义类比较器

java 自定义类比较器

示例：

package com.myfile;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * Created by tengfei on 2017/10/27
 */
public class CompareTest {
    /**
     * 内部比较器：Comparable, 重写conpareTo方法
     */
    @SuppressWarnings("rawtypes")
    class Student1 implements Comparable {
        private String name;
        private int age;

        public Student1(int age, String name) {
            this.age = age;
            this.name = name;
        }

        @Override
        public String toString() {
            return "\tStudent1 age: " + age + ", name: " + name + "\r";
        }

        @Override
        public int compareTo(Object o) {
            Student1 tmp = (Student1) o;
            int result = tmp.age < age ? 1 : (tmp.age == age ? 0 : -1);
            return result = result == 0 ? (tmp.name.trim().compareTo(name.trim()) < 0 ? 1 : -1) : result;
        }
    }

    // -------------------------------------------------------------------------------------

    /**
     * 外部比较器：Comparator, 定义comparator比较类
     */
    class Student2 {
        private String name;
        private int age;

        public Student2(int age, String name) {
            this.age = age;
            this.name = name;
        }

        @Override
        public String toString() {
            return "\tStudent2 age: " + age + ", name: " + name + "\r";
        }
    }

    @SuppressWarnings("rawtypes")
    public static class Student2Comparator implements Comparator {
        public int compare(Object o1, Object o2) {
            Student2 t1 = (Student2) o1;
            Student2 t2 = (Student2) o2;
            int result = t1.age > t2.age ? 1 : (t1.age == t2.age ? 0 : -1);
            return result = result == 0 ? (t1.name.trim().compareTo(t2.name.trim()) > 0 ? 1 : -1) : result;
        }

        @SuppressWarnings("unchecked")
        public static void main(String[] args) {
            CompareTest co = new CompareTest();
            List<Student1> list1 = new ArrayList<Student1>();
            list1.add(co.new Student1(1, "aa"));
            list1.add(co.new Student1(2, "abb"));
            list1.add(co.new Student1(2, "acc"));
            list1.add(co.new Student1(3, "dd"));
            Collections.sort(list1); // 内部比较器:要排序的对象实现Comparable接口,可以对自身进行比较
            System.out.println(list1);

            List<Student2> list2 = new ArrayList<Student2>();
            list2.add(co.new Student2(1, "aa"));
            list2.add(co.new Student2(2, "abb"));
            list2.add(co.new Student2(2, "acc"));
            list2.add(co.new Student2(3, "dd"));
            Collections.sort(list2, new Student2Comparator()); // 外部比较器:通过实现Comparator接口
            System.out.println(list2);
        }
    }
}