java 8 Lambda 表达式和 streamAPI小练习

我就是我 2023-07-18 02:36 23阅读 0赞

package com.mall.demo.controller;

import java.util.\*;  
import java.util.stream.Collectors;

public class Java8Tester \{  
public static void main(String\[\] args) \{  
ArrayList names1 = new ArrayList();  
names1.add(“Google”);  
names1.add(“Runoob”);  
names1.add(“Taobao”);  
names1.add(“Baidau”);  
names1.add(“Baidu”);  
names1.add(“Baicdu”);  
names1.add(“Sina”);  
names1.add("");  
names1.add("");  
names1.add("");

Java8Tester java8Tester = new Java8Tester();
        System.out.println("未排序"+names1);
        java8Tester.useJava8(names1);
        System.out.println("使用java8 排序"+names1);
        long count = names1.stream().filter(s -> s.isEmpty()).count();
        System.out.println("空字符串数量为"+count);
        long count1 = names1.stream().filter(s -> s.length()==4).count();
        System.out.println("字符串长度为4有"+count1+"个");
        List<String> collect = names1.stream().filter(s -> !s.isEmpty()).collect(Collectors.toList());
        System.out.println("筛选后的列表"+collect);
        //合并字符串
        String collect1 = names1.stream().filter(s -> !s.isEmpty()).collect(Collectors.joining("-"));
        System.out.println("- __ -"+collect1);
    
        List<Integer> numbers = Arrays.asList(3, 2, 2, 3, 7, 3, 5);
        Object collect2 = numbers.stream().map(i -> i * i).distinct().collect(Collectors.toList());
        System.out.println("列表"+collect2);
        IntSummaryStatistics intSummaryStatistics = numbers.stream().mapToInt(i -> i).summaryStatistics();
        System.out.println("summaryStatistics"+intSummaryStatistics);
    
        Random random = new Random();
        random.ints().limit(10).forEach(System.out::println);
    
    }
    private void useJava8(List<String> names){
        Collections.sort(names,(o1, o2) -> o1.compareTo(o2));
    }

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