java8 Lambda学习

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原文地址：https://www.cnblogs.com/xiaoxi/p/7099667.html
原文更详细，我只是记录一下自己的代码

public class Persion {

     String name;
     LocalDate localDate;

    public Persion(String name,LocalDate localDate){
        this.name = name;
        this.localDate = localDate;
    }

    public static int  compareByAge(Persion p ,Persion p1){
        return p.localDate.compareTo(p1.localDate);
    }

    @Override
    public String toString() {
        return this.name;
    }
}

public static void main(String[] args) {

        Persion p1 = new Persion("小明", LocalDate.of(2018,6,6));
        Persion p2 = new Persion("小红", LocalDate.of(2018,4,6));
        Persion p3 = new Persion("小白", LocalDate.of(2018,6,22));


        Persion [] p = new Persion[]{p1,p2,p3};

        //不使用lambda表达式
        Arrays.sort(p, new Comparator<Persion>() {
            @Override
            public int compare(Persion o1, Persion o2) {
                return o1.localDate.compareTo(o2.localDate);
            }
        });

        //使用Lambda表达式 不简化的方式
        Arrays.sort(p,(Persion pp1, Persion pp2) -> {return pp1.localDate.compareTo(pp2.localDate);});

        //使用Lambda表达式 简化的方式 (可以省略Persion)
        Arrays.sort(p,(pp1,pp2) -> pp1.localDate.compareTo(pp2.localDate));

        //使用Lambda表达式使用静态方法的引用 (其实是调用了Perion的compareByAge不需要传参数)
        Arrays.sort(p,Persion::compareByAge);

        System.out.println(Arrays.asList(p));

        Map<Long,Double> roleServiceCountMap = new HashMap<>();
        roleServiceCountMap.put(1000L,34.2);
        roleServiceCountMap.put(2000L,120.34);
        roleServiceCountMap.put(3000L,38.98);

        List<Map.Entry<Long, Double>> list = new ArrayList<Map.Entry<Long,Double>>(roleServiceCountMap.entrySet());

        Collections.sort(list,(o1, o2) -> BigDecimal.valueOf(o1.getValue()).compareTo(BigDecimal.valueOf(o2.getValue())));

        list.forEach(item -> System.out.println(item.getKey()+"=="+item.getValue()));

    }