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comparingComparator<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));
https://gitee.com/play-happy/base-project
参考：
【1】《Java8实战》
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本文标题: Java8 用Lambda表达式给List集合排序的实现
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