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  • 列表处理

    package com.io.demo1;

    import java.util.Arrays;
    import java.util.List;
    import java.util.Random;
    import java.util.stream.Collectors;

    public class TestChar {
    public static void main(String[] args) {

    List<Integer> list = Arrays.asList(1, 2, 3, 4);

    Random random = new Random();

    // limit用法
    random.ints().limit(10).forEach(System.out::println);

    // map处理并去重
    List<Integer> number = Arrays.asList(3, 2, 2, 3, 7, 3, 5);
    /*
    List<Integer> collect = number.stream().map(item -> item * item).distinct().collect(Collectors.toList());
    System.out.println(collect);
    */

    //大于10的数字
    List<Integer> collect = number.stream().filter(item -> item > 3).collect(Collectors.toList());
    System.out.println(collect);

    // filter用法
    List<String> strings = Arrays.asList("abc", "", "bc", "bc", "efg", "abcd", "", "jkl");
    long count = strings.stream().filter(item -> !item.isEmpty()).distinct().count();
    System.out.println("非空数字的总数" + count);
    long count1 = strings.parallelStream().filter(item -> item.isEmpty()).count();
    System.out.println("并行处理结果:" + count1);

    /**
    * php关系数组
    * javascript es6的话,都是用=> 箭头符号
    */
    //strings.stream().filter(item->!item.isEmpty()).forEach(System.out::println);

    /**
    * collect 汇总下结果,joining转为字符串
    */
    String toy = strings.stream().filter(item -> !item.isEmpty()).collect(Collectors.joining("雷"));
    System.out.println(toy);

    // 用","号连接,并且给这个字符串加个前缀与后缀
    String collect1 = strings.stream().filter(item -> !item.isEmpty()).collect(Collectors.joining(",", "中", "国"));
    System.out.println(collect1);

    // foreach 与sorted应用
    random.ints().limit(10).sorted().forEach(System.out::println);


    }
    }


    package com.io.demo1;

    import java.util.Arrays;
    import java.util.Comparator;
    import java.util.List;
    import java.util.Optional;
    import java.util.function.Function;

    /**
    * 文件字节流
    */
    public class TestFileio {
    public static void main(String[] args) {

    List<Integer> integers = Arrays.asList(1, 2, 3);

    Optional<Integer> max = integers.stream().max(Comparator.comparing(Function.identity()));
    System.out.println(max.get());

    Optional<Integer> min = integers.stream().min(Comparator.comparing(Function.identity()));
    System.out.println(min.get());


    // 返反一个最大值 ,用lamba表达式
    Optional<Integer> max1 = integers.stream().max((x, y) -> x.compareTo(y));
    System.out.println(max1.get());


    // 获取第一个值
    Optional<Integer> first = integers.stream().findFirst();
    System.out.println(first.get());

    System.out.println(integers.get(0));
    }
    }


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  • 原文地址:https://www.cnblogs.com/leigepython/p/10696812.html
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