java8新特性练手--从菜鸟教程中

Posted 2020-12-05 512178509

package com.fh.jdk8;

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

import org.junit.Test;

public class Learning01 {

    @Test
    public void sort() {
        List<String> list = new ArrayList<>();
        list.add("feng");
        list.add("hao");
        list.add("haha");
        list.add("xixi");
        sort7(list);
        sort8(list);
    }
    
    public void sort7(List<String> list) {
        Collections.sort(list, new Comparator<String>() {

            @Override
            public int compare(String o1, String o2) {
                return o1.compareTo(o2);
            }
            
        });
        for (String string : list) {
            System.out.println(string);
        }
    }
    public void sort8(List<String> list) {
        Collections.sort(list, (o1,o2) -> o1.compareTo(o2));
        list.forEach(demo ->{
            System.out.println(demo);
        });
    }
    
    /**
     * lambda表达式学习--闭包
     */
    @Test
    public void lambda() {
        Learning01 instance = new Learning01();
        MathOperation add = (int a,int b) -> a+b;
        MathOperation sub = (a,b) ->a-b;
        MathOperation mul = (a,b) ->{return a * b;};
        MathOperation div = (a,b) -> a/b;
        System.out.println(instance.operator(1, 2, add));
        
        
        GreetingService service = (message) ->
        System.out.println("hello "+message);
        
        service.sayMessgae("hahah");
    }
    
    public int operator(int a,int b,MathOperation mathOperation) {
        return mathOperation.operation(a, b);
    }
    
    interface MathOperation {
        int operation(int a,int b);
    }
    
    interface GreetingService {
        void sayMessgae(String message);
    }
    

    @Test
    public void test22() {
        Person person = new Man();
        person.print();
        
    }

}

package com.fh.jdk8;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.Month;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.Arrays;
import java.util.Base64;
import java.util.IntSummaryStatistics;
import java.util.List;
import java.util.Random;
import java.util.UUID;
import java.util.stream.Collectors;

import org.junit.Test;

/**
 * Stream API test
 * @author Administrator
 *
 */
public class Learning02 {

    @Test
    public void test01() {
        List<String> list = Arrays.asList("1","2","3","","4","5","6");
        List<String> collect = list.stream().filter(demo ->!demo.isEmpty()).collect(Collectors.toList());
        collect.forEach(demo ->{
            System.out.println(demo);
        });
    }
    
    @Test
    public void test02() {
        Random random = new Random();
        random.ints().limit(1).forEach(System.out::println);
    }
    
    @Test
    public void test03() {
        List<Integer> asList = Arrays.asList(2,2,3,4,5,6,7);
        List<Integer> collect = asList.stream().map(demo -> demo*demo).distinct().collect(Collectors.toList());
        collect.forEach(demo ->{
            System.out.println(demo);
        });
        System.out.println("*********");
        collect.stream().filter(demo -> demo>5).collect(Collectors.toList()).forEach(demo->{
            System.out.println(demo);
        });
    }
    
    @Test
    public void test04() {
        List<String> list = Arrays.asList("ha","niin","hhh","jj","ll");
        String string = list.parallelStream().findFirst().get();
        System.out.println(string);
    }
    
    @Test
    public void test05() {
        List<String> list = Arrays.asList("ha","niin","hhh","jj","ll");
        String string = list.parallelStream().filter(demo ->!demo.isEmpty()).collect(Collectors.joining(","));
        System.out.println(string);
    }
    
    @Test
    public void test06() {
        List<Integer> list = Arrays.asList(2,3,4,5,6,6,7,8,8,8,8,8);
        IntSummaryStatistics summer = list.stream().mapToInt(demo ->demo).summaryStatistics();
        System.out.println("average:"+summer.getAverage());
        System.out.println("count:"+summer.getCount());
        System.out.println("max:"+summer.getMax());
        System.out.println("min:"+summer.getMin());
        System.out.println("sum:"+summer.getSum());
    }
    
    @Test
    public void test07() {
        LocalDateTime currentTime = LocalDateTime.now();
//        System.out.println(currentTime);
//        System.out.println(currentTime.toLocalDate());
//        System.out.println(currentTime.toLocalTime());
        Month month = currentTime.getMonth();
        int day = currentTime.getDayOfMonth();
        int second = currentTime.getSecond();
//        System.out.println("月:"+month+"天:"+day+"秒:"+second);
        
        LocalDateTime withYear = currentTime.withDayOfMonth(10).withYear(2018);
//        System.out.println("withDayOfMonth:"+withYear);
        /*2018-07-20T15:18:33.054
        2018-07-20
        15:18:33.054
        月:JULY天:20秒:33
        withDayOfMonth:2018-07-10T15:18:33.054*/
        LocalDate of = LocalDate.of(2018, Month.DECEMBER, 20);
        System.out.println(of);
        
        LocalTime times = LocalTime.of(12, 12);
        System.out.println(times);
        
        LocalTime parse = LocalTime.parse("15:22:22");
        System.out.println(parse);
    }
    
    @Test
    public void test08() {
        ZonedDateTime parse = ZonedDateTime.parse("2015-12-03T10:15:30+05:30[Asia/Shanghai]");
        System.out.println(parse);
        
        ZoneId of = ZoneId.of("Europe/Paris");
        System.out.println(of);
        
        ZoneId systemDefault = ZoneId.systemDefault();
        System.out.println(systemDefault);
    }
    
    @Test
    public void test09() {
        try {
            //编码
            String encodeToString = Base64.getEncoder().encodeToString("run?java8".getBytes("utf-8"));
            System.out.println(encodeToString);
            //解码
            byte[] decode = Base64.getDecoder().decode(encodeToString);
            System.out.println(new String(decode,"utf-8"));
            
            String urlEncoder = Base64.getUrlEncoder().encodeToString("http://baidu.com".getBytes("utf-8"));
            System.out.println(urlEncoder);
            
            StringBuilder builder = new StringBuilder();
            for (int i = 0; i < 20; i++) {
                builder.append(UUID.randomUUID().toString());
            }
            String mime = Base64.getMimeEncoder().encodeToString(builder.toString().getBytes("utf-8"));
            System.out.println(mime);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


}