Guava系列：Ordering使用方法（单元素、对象多属性排序）

目录

​​应用场景​​

​​单元素​​

​​top N查询​​

​​对象多属性排序​​

​​补充：默认多个字段排序​​

应用场景

排序：单元素、对象多属性排序

单元素

package com.nio4444.demo;

import com.google.common.collect.Lists;
import com.google.common.collect.Ordering;

import java.util.Collections;
import java.util.List;

public class OrderingDemo {
    public static void main(String[] args) {
        List list = Lists.newArrayList() ;
        list.add(new Integer(4));
        list.add(new Integer(1));
        list.add(new Integer(3));
        list.add(new Integer(2));
        list.add(new Integer(6));
        list.add(new Integer(8));
        list.add(new Integer(7));

        Collections.sort(list);
        System.out.println("默认\n"+list);

        Ordering ordering = Ordering.natural();
        Collections.sort(list,ordering);
        System.out.println("\nordering\n"+list);
        System.out.println("min、max："+ordering.min(list)+" "+ordering.max(list));

        Collections.sort(list,ordering.reverse());
        System.out.println("\nreverse\n"+list);


    }
}

top N查询

package com.nio4444.demo;

import com.google.common.collect.Lists;
import com.google.common.collect.Ordering;

import java.util.Collections;
import java.util.List;

public class OrderingDemo {
    public static void main(String[] args) {
        List list = Lists.newArrayList() ;
        list.add(new Integer(4));
        list.add(new Integer(1));
        list.add(new Integer(3));
        list.add(new Integer(2));
        list.add(new Integer(6));
        list.add(new Integer(8));
        list.add(new Integer(7));

        Collections.sort(list);
        System.out.println("默认\n"+list);

        Ordering ordering = Ordering.natural();
        System.out.println("\ngreatestOf top3: "+ordering.greatestOf(list,3));
        System.out.println("\nleastOf top3: "+ordering.leastOf(list,3));


    }
}

对象多属性排序

package com.nio4444.demo;

import com.google.common.collect.Lists;
import com.google.common.collect.Ordering;
import lombok.AllArgsConstructor;
import lombok.Data;

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

public class OrderingDemo {
    public static void main(String[] args) {
        List list = Lists.newArrayList() ;
        list.add(new Person(4,"44"));
        list.add(new Person(1,"11"));
        list.add(new Person(3,"33"));
        list.add(new Person(7,"33"));
        list.add(new Person(5,"55"));
        list.add(new Person(3,"00"));

        System.out.println("\n---------------list------\n" + list);


        System.out.println("\n---------------age------" );
        Ordering nameOrdering = Ordering.from(new AgeComp());
        Collections.sort(list,nameOrdering);
        System.out.println("\nordering\n"+list);
        System.out.println("min、max："+nameOrdering.min(list)+" "+nameOrdering.max(list));

        Collections.sort(list,nameOrdering.reverse());
        System.out.println("\nreverse\n"+list);


        System.out.println("\n--------------- name & age-----" );
        Ordering nameAgeOrdering = Ordering.from(new NameComp()).compound(new AgeComp());
        Collections.sort(list,nameAgeOrdering);
        System.out.println("\nordering\n"+list);
        System.out.println("min、max："+nameAgeOrdering.min(list)+" "+nameAgeOrdering.max(list));

        Collections.sort(list,nameAgeOrdering.reverse());
        System.out.println("\nreverse\n"+list);
    }

}

@Data
@AllArgsConstructor
class Person{
    private int age ;
    private String name ;
}

class AgeComp implements Comparator<Person>{
    @Override
    public int compare(Person o1, Person o2) {
        return o1.getAge()-o2.getAge();
    }
}

class NameComp implements Comparator<Person>{
    @Override
    public int compare(Person o1, Person o2) {
        return o1.getName().compareTo(o2.getName());
    }
}

补充：默认多个字段排序