zoukankan      html  css  js  c++  java
  • java List对象排序

    Lambda用到了JDK8自带的一个函数式接口Comparator<T>。

    准备一个Apple类

    public class Apple {
        private int weight;
        private String color;
    
        public Apple(){}
    
        public Apple(int weight) {
            this.weight = weight;
        }
    
        public Apple(int weight, String color) {
            this.weight = weight;
            this.color = color;
        }
        
        setters();getters();toString();  
    }
    

     

    步骤一:

    public class AppleComparator implements Comparator<Apple> {
        @Override
        public int compare(Apple o1, Apple o2) {
            return o1.getWeight() - o2.getWeight();
        }
    }
    

      

    步骤二:准备一个List集合

    ArrayList<Apple> inventory = Lists.newArrayList(
                    new Apple(10, "red"),
                    new Apple(5, "red"),
                    new Apple(1, "green"),
                    new Apple(15, "green"),
                    new Apple(2, "red"));
    

      

    步骤三:顺序排序,三种方式

    /**
     * 顺序排序
     */
    // 1、传递代码,函数式编程
    inventory.sort(new AppleComparator());
    System.out.println(inventory);
    
    // 2、匿名内部类
    inventory.sort(new Comparator<Apple>() {
        @Override
        public int compare(Apple o1, Apple o2) {
            return o1.getWeight() - o2.getWeight();
        }
    });
    
    // 3、使用Lambda表达式
    inventory.sort((a, b) -> a.getWeight() - b.getWeight());
    
    // 4、使用Comparator的comparing
    Comparator<Apple> comparing = comparing((Apple a) -> a.getWeight());
    inventory.sort(comparing((Apple a) -> a.getWeight()));
    //或者等价于
    inventory.sort(comparing(Apple::getWeight));
    

      

     步骤四:逆序排序

    /**
     * 逆序排序
     */
    // 1、 根据重量逆序排序
    inventory.sort(comparing(Apple::getWeight).reversed()); 
    

      

    步骤五:如果两个苹果一样重,就得再找一个条件来进行排序、

    // 2、如果两个苹果的重量一样重,怎么办?那就再找一个条件进行排序呗
    inventory.sort(comparing(Apple::getWeight).reversed().thenComparing(Apple::getColor));
    

      

  • 相关阅读:
    空间轴向对齐变换
    购买服务器,搭建服务器服务器
    软件工程第四次作业:猫狗大战挑战赛
    软件工程第三次作业:卷积神经网络
    04卷积神经网络
    03深度学习的数学基础
    mfc回显信息
    软件工程第二次作业:深度学习和pytorch基础
    python 机器学习第二章(感知器学习算法)
    python 机器学习第一章
  • 原文地址:https://www.cnblogs.com/jiehanshi/p/12611073.html
Copyright © 2011-2022 走看看