Java8:Lambda-Comparator

原文链接

经典的比较方法：

Comparator byName = new Comparator() {
    @Override
    public int compare(Developer o1, Developer o2) {
        return o1.getName().compareTo(o2.getName());
    }
};

对应使用Lambda表达式实现该方法：

Comparator byName =  (Developer o1, Developer o2)->o1.getName().compareTo(o2.getName());

---

例子：
1. 不使用Lambda表达式：

package com.mkyong.java8;

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

public class TestSorting {
    public static void main(String[] args) {
        List listDevs = getDevelopers();

        System.out.println("Before Sort");
        for (Developer developer : listDevs) {
            System.out.println(developer);
        }

        //sort by age
        Collections.sort(listDevs, new Comparator() {
            @Override
            public int compare(Developer o1, Developer o2) {
                return o1.getAge() - o2.getAge();
            }
        });

        System.out.println("After Sort");
        for (Developer developer : listDevs) {
            System.out.println(developer);
        }

    }

    private static List getDevelopers() {
        List result = new ArrayList();
        result.add(new Developer("mkyong", new BigDecimal("70000"), 33));
        result.add(new Developer("alvin", new BigDecimal("80000"), 20));
        result.add(new Developer("jason", new BigDecimal("100000"), 10));
        result.add(new Developer("iris", new BigDecimal("170000"), 55));
        return result;
    }
}

1. 使用Lambda表达式：

package com.mkyong.java8;

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;

public class TestSorting {
    public static void main(String[] args) {
        List listDevs = getDevelopers();

        System.out.println("Before Sort");
        for (Developer developer : listDevs) {
            System.out.println(developer);
        }

        System.out.println("After Sort");

        //lambda
        //listDevs.sort((o1, o2)->o1.getName().compareTo(o2.getName()));

        //lambda
        listDevs.sort((Developer o1, Developer o2)->o1.getAge()-o2.getAge());

        //java 8 only, lambda also, to print the List
        listDevs.forEach((developer)->System.out.println(developer));
    }

    private static List<Developer> getDevelopers() {
        List<Developer> result = new ArrayList<Developer>();
        result.add(new Developer("mkyong", new BigDecimal("70000"), 33));
        result.add(new Developer("alvin", new BigDecimal("80000"), 20));
        result.add(new Developer("jason", new BigDecimal("100000"), 10));
        result.add(new Developer("iris", new BigDecimal("170000"), 55));
        return result;
    }
}