java8笔记一

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package com;import java.util.*;import java.util.function.Predicate;import java.util.regex.Matcher;import java.util.regex.Pattern;import java.util.stream.Collectors;import java.util.stream.IntStream;/** * @author nidayu * @Description: 测试Java8特性 * @date 2015/10/8 */public class TestJava8 {    //不包含的集合！    private static Set NON_WORDS = new HashSet<String>(){{add("ni"); add("DA"); add("yu");}};    public Map wordFreq(String words){        TreeMap<String, Integer> wordMap = new TreeMap<String, Integer>();        Matcher m = Pattern.compile("\\w+").matcher(words);        while(m.find()){            String word = m.group().toLowerCase();            if (!NON_WORDS.contains(word)){                if (wordMap.get(word) == null){                    wordMap.put(word, 1);                }else{                    wordMap.put(word, wordMap.get(word) + 1);                }            }        }        return wordMap;    }    public static void main(String[] args){        //初始化List        List<String> places = Arrays.asList("Buenos Aires", "Córdoba", "La Plata");        places.stream().filter(name -> name.startsWith("C")).forEach(name -> System.out.println(name));        //排序        List<Integer> comList = new ArrayList<>();        comList.add(1);comList.add(0);comList.add(3);comList.add(7);comList.add(6);comList.add(5);        Comparator<Integer> c1 = (x, y) -> x-y;        Comparator<Integer> c2 = c1.reversed();        Comparator<Integer> c3 = (x, y) -> y-x;        System.out.println(                comList.stream()                        .min((x, y) -> x - y)                        .get()        );        System.out.println("min = " + comList.stream().min(c1).get());        System.out.println("max = " + comList.stream().max(c1).get());        System.out.println("max = " + comList.stream().min(c2).get());        System.out.println("max = " + comList.stream().min(c3).get());        //方法覆盖        new Thread(() -> System.out.println("hello, world")).start();        //过滤循环输出        Predicate<String> p = name -> !name.startsWith("Mr");        List l = new ArrayList<String>();        l.add("Mr Ni");l.add("Ms Zhang");l.add("Ms Lv");l.add("Ms Wang");        l.stream().filter(p).forEach(name -> System.out.println(name));        //找完美数        System.out.println(                IntStream.range(1, 12).filter(t -> 12%t == 0).sum()        );        //过滤拼接        List<String> list = new ArrayList<String>();        list.add("ni");        list.add("da");        list.add("yu");        list.add("ni");        System.out.println(                list.parallelStream() //并发的，和stream()不一样                        .filter(name -> name!=null)                        .filter(name -> name.length()>1)                        .map(name -> name.substring(0, 1).toUpperCase()+name.substring(1, name.length()))                        .collect(Collectors.joining(","))        );        //循环遍历        List<String> list1 = new ArrayList<String>();        list.stream().filter(w -> !NON_WORDS.contains(w)).forEach(w -> list1.add(w));        for (int i=0;i<list1.size();i++){            System.out.println(list1.get(i));        }        //统计！        TreeMap<String, Integer> wordMap = new TreeMap<String, Integer>();        list.stream().map(w -> w.toUpperCase())                .filter(w -> !NON_WORDS.contains(w))                .forEach(w -> wordMap.put(w, wordMap.getOrDefault(w, 0) + 1));        for (String key: wordMap.keySet()){            System.out.println(key + " ... "+wordMap.get(key));        }    }}
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