lambda表达式实战

/** * ClassName:LambdaInAction <br/> * Function: TODO ADD FUNCTION. <br/> * Reason: TODO ADD REASON. <br/> * Date: 2017年9月10日 下午8:12:49 <br/> *  * @author: Lelonta * @version * @see */public class LambdaInAction {//  @Test    public void map() {        //转换        String queryString = "name=lelonta&id=100000&password=123456";        Map<String, String> map = Stream.of(queryString.split("&"))                .map(str -> str.split("="))                .collect(Collectors.toMap(str -> str[0], str -> str[1]));        System.out.println("map=" + map);    }    // str -> str.split("=")    public String[] getSplit(String str) {        return str.split("=");    }//  @Test    public void getId() {        List<Integer> list = books().stream().map(book -> book.getId())                .collect(Collectors.toList());        System.out.println("list=" + list);        list = books().stream().map(Book::getId).collect(Collectors.toList());        System.out.println("list=" + list);        String str = books().stream().map(book -> book.getId() + "")                .collect(Collectors.joining(","));        System.err.println("str=" + str);    }//  @Test    public void getType() {        List<String> list = books().stream().map(book -> book.getType())                .collect(Collectors.toList());        System.out.println("list=" + list);        list = books().stream().map(book -> book.getType()).distinct()                .collect(Collectors.toList());        System.out.println("去重后的list=" + list);    }    public void setOrder() {        // 价格从低到高        // books().stream()        // .sorted((book1, book2) -> Double.compare(book1.getPrice(),        // book2.getPrice())).forEach(System.out::println);        // 从高到低        Comparator<Book> comparator = (book1, book2) -> Double.compare(                book1.getPrice(), book2.getPrice());        books().stream().sorted(comparator.reversed())                .forEach(System.out::println);        // 简化的方法        books().stream().sorted(Comparator.comparing(Book::getPrice))                .forEach(System.out::println);    }    // 多条件排序    public void setOrderCom() {        Comparator<Book> comparator = (book1, book2) -> Double.compare(                book1.getPrice(), book2.getPrice());        books().stream()                .sorted(comparator.thenComparing((book1, book2) -> book1                        .getPublishDate().isAfter(book2.getPublishDate()) ? 1                        : -1)).forEach(System.out::println);        books().stream()                .sorted(Comparator.comparing(Book::getPrice).thenComparing(                        Comparator.comparing(Book::getPublishDate)))                .forEach(System.out::println);    }    public void bookToMap() {        Map<Integer, Book> map = books().stream().collect(                Collectors.toMap(book -> book.getId(), book -> book));        System.out.println(map);    }//  @Test    public void avage() {        Double d = books().stream().collect(                Collectors.averagingDouble(Book::getPrice));        System.out.println(d);    }//  @Test    public void maxormin() {        Optional<Book> bookOptional = books().stream().collect(                Collectors.maxBy(Comparator.comparing(Book::getPrice)));        System.out.println(bookOptional);        bookOptional = books().stream().collect(                Collectors.minBy(Comparator.comparing(Book::getPrice)));        System.out.println(bookOptional);    }//  @Test    public void group() {        // 按类型分组        Map<String, List<Book>> map = books().stream().collect(                Collectors.groupingBy(Book::getType));        map.keySet().forEach(key -> {            System.out.println(key);            System.out.println(map.get(key));            System.out.println("---------------------------");        });    }    // 统计数量//  @Test    public void count() {        Map<String, Long> map = books().stream().collect(                Collectors.groupingBy(Book::getType, Collectors.counting()));        System.out.println(map);    }//  @Test    public void sum() {        // 每种类型的总价格        Map<String, Double> d = books().stream().collect(                Collectors.groupingBy(Book::getType,                        Collectors.summingDouble(Book::getPrice)));        System.out.println(d);    }//  @Test    public void high() {        // 每种类型最贵的        Map<String, Optional<Book>> d = books().stream()                .collect(                        Collectors.groupingBy(Book::getType, Collectors                                .maxBy(Comparator.comparing(Book::getPrice))));        System.out.println(d);    }//  @Test    public void filter() {        books().stream().filter(book -> book.getPrice() >= 50)                .sorted(Comparator.comparing(Book::getPublishDate).reversed())                .forEach(System.out::println);    }    private List<Book> books() {        List<Book> books = new ArrayList<Book>();        books.add(new Book(1, "java", 50, "java", LocalDate.parse("2017-09-10")));        books.add(new Book(2, "python", 51, "python", LocalDate                .parse("2017-09-10")));        books.add(new Book(3, "jsp", 52, "jsp", LocalDate.parse("2017-09-10")));        books.add(new Book(4, "php", 53, "php", LocalDate.parse("2017-09-10")));        books.add(new Book(5, "js", 54, "js", LocalDate.parse("2017-09-10")));        return books;    }    public static void main(String[] args) {        String queryString = "name=lelonta&id=100000&password=123456";        Map<String, String> map = Stream.of(queryString.split("&"))                .map(str -> str.split("="))                .collect(Collectors.toMap(str -> str[0], str -> str[1]));        System.out.println("map=" + map);//map={password=123456, name=lelonta, id=100000}        String queryString1 = "name=lelonta&id=100000&password=123456";        String[] str = queryString.split("&");//      System.out.println(str);        Map map1 = new HashMap();        for (String str1:str) {//          System.out.println(str1);            String[] str2 = str1.split("=");            map.put("key",str2[0]);            map.put("value",str2[1]);        }        System.out.println(map);    }}