java8新特性，stream流简单使用

//新建测试类

@Data
@NoArgsConstructor
@AllArgsConstructor
@EqualsAndHashCode
public class Author {
    //id
    private Long id;
    //姓名
    private String name;
    //年龄
    private Integer age;
    //简介
    private String intro;
    //作品
    private List<Book> books;
}

@Data
@NoArgsConstructor
@AllArgsConstructor
@EqualsAndHashCode//用于后期的去重使用
public class Book {
    //id
    private Long id;
    //书名
    private String name;

    //分类
    private String category;

    //评分
    private Integer score;

    //简介
    private String intro;
}


//代码示例

/**
 * 获取任意一个年龄大于18的作家，如果存在就输出他的名字
 */
@Test
public void test18(){
    List<Author> list = getAuthors();
    Optional<Author> optionalS = list.stream()
            .filter(author -> author.getAge()  > 18)
            .findAny();
    System.out.println(optionalS.get());
}


/**
 *  判断作家是否都没有超过100岁的。
 */
@Test
public void test17(){
    List<Author> list = getAuthors();
    boolean flag = list.stream().noneMatch(author -> author.getAge() > 100);
    System.out.println(flag);
}


/**
 * 判断是否所有的作家都是成年人
 */
@Test
public void test16(){
    List<Author> list = getAuthors();
    boolean flag = list.stream().allMatch(author -> author.getAge() >= 18);
    System.out.println(flag);
}



/**
 * 判断是否有年龄在29以上的作家
 */
@Test
public void test15(){
    List<Author> list = getAuthors();
    boolean flag = list.stream().anyMatch(author -> author.getAge() > 35);
    System.out.println(flag);
}


/**
 * 获取一个Map集合，map的key为作者名，value为List<Book>
 */
@Test
public void test14(){
    List<Author> list = getAuthors();
    Map<String,Object> map = list.stream()
            .distinct()
            .collect(Collectors.toMap
            (author -> author.getName(), author -> author.getBooks()
                    .stream().map(a->a.getName())
                    .distinct()
                    .collect(Collectors.toList())));
    System.out.println(map);
}

/**
 * 获取一个所有书名的Set集合
 */
@Test
public void test13(){
    List<Author> list = getAuthors();
    Set<Book> strings = list.stream().flatMap(author -> author.getBooks().stream())
            .collect(Collectors.toSet());
    Set<String> strings2 = list.stream().flatMap(author -> author.getBooks().stream())
            .map(a->a.getName())
            .distinct()
            .collect(Collectors.toSet());
    System.out.println(strings2);
}


/**
 * 获取一个存放所有作者名字的List集合。
 */
@Test
public void test12(){
    List<Author> list = getAuthors();
    List<String> strings = list.stream().map(author -> author.getName())
            .distinct()
            .collect(Collectors.toList());
    System.out.println(strings);
}

/**
 * 分别获取这些作家的所出书籍的最高分和最低分并打印
 */
@Test
public void test11(){
    List<Author> list = getAuthors();
    Optional<Integer> strings = list.stream().flatMap(author -> author.getBooks().stream())
            .map(a->a.getScore())
            .max((s1,s2)->s1 - s2);
    Optional<Integer> strings2 = list.stream().flatMap(author -> author.getBooks().stream())
            .map(a->a.getScore())
            .min((s1,s2)->s1 - s2);
    System.out.println(strings.get() + "---" +strings2.get());


}


/**
 * 打印这些作家的所出书籍的数目，注意删除重复元素
 */
@Test
public void test10(){
    List<Author> list = getAuthors();
    long count = list.stream().flatMap(author -> author.getBooks().stream())
            .distinct()
            .count();
    System.out.println(count);
}

/**
 * 打印现有书籍的所有分类。要求对分类进行去重。不能出现这种格式：哲学,爱情
 */
@Test
public void test09(){
    List<Author> list = getAuthors();
    List<String> strings = list.stream()
            .flatMap(author -> author.getBooks().stream())
            .distinct()
            .flatMap(a->Arrays.stream(a.getCategory().split(",")))
            .collect(Collectors.toList());
    for (String s : strings){
        System.out.println(s);
    }

}


/**
 * 打印所有书籍的名字。要求对重复的元素进行去重。
 */
@Test
public void test08(){
    List<Author> list = getAuthors();
    List<String> strings = list.stream()
            .flatMap(author -> author.getBooks().stream())
            .distinct()
            .map(a->a.getName())
            .collect(Collectors.toList());
    for (String author : strings){
        System.out.println(author);
    }
}

/**
 * 打印除了年龄最大的作家外的其他作家，要求不能有重复元素，并且按照年龄降序排序
 */
@Test
public void test07(){
    List<Author> list = getAuthors();
    List<Author> authors = list.stream().distinct()
            .sorted((a1,a2) ->a2.getAge() - a1.getAge())
            .skip(1)
            .collect(Collectors.toList());
    for (Author author : authors){
        System.out.println(author);
    }
}

/**
 * 对作家进行年龄排序，不能有重复.并且打印年龄最大的一个作家
 */
@Test
public void test06(){
    List<Author> list = getAuthors();
    List<Author> authors = list.stream().distinct()
            .sorted((a1,a2) ->a2.getAge() - a1.getAge())
            .limit(1)
            .collect(Collectors.toList());
    for (Author author : authors){
        System.out.println(author);
    }
}

/**
 * 对作家进行年龄排序，不能有重复
 */
@Test
public void test05(){
    List<Author> list = getAuthors();
    List<Author> authors = list.stream().distinct()
            .sorted((o1,o2)->o2.getAge() - o1.getAge())
            .collect(Collectors.toList());

    for (Author author : authors){
        System.out.println(author);
    }
}


/**
 * 打印所有作家的姓名,不能有重复的姓名
 */
@Test
public void test04(){
    List<Author> list = getAuthors();
    List<String> strings = list.stream().map(author -> author.getName())
            .distinct()
            .collect(Collectors.toList());
    for (String author : strings){
        System.out.println(author);
    }
}


/**
 * 打印所有作家的姓名
 */
@Test
public void test03(){
    List<Author> list = getAuthors();
    List<String> authors = list.stream().map(author -> author.getName()).collect(Collectors.toList());
    for (String author : authors){
        System.out.println(author);
    }

}

/**
 * 打印说明姓名长度大于1的作家
 */
@Test
public void test02(){
    List<Author> list = getAuthors();
    List<Author> authors = list.stream().filter(author -> author.getName().length() > 1).collect(Collectors.toList());
    for (Author author : authors){
        System.out.println(author);
    }
}


/**
 * 打印所有年龄小于18的作者
 */
@Test
public void test01(){
    List<Author> list = getAuthors();
    List<Author> authors = list.stream().filter(author -> author.getAge() < 18).collect(Collectors.toList());
    for (Author author : authors){
        System.out.println(author);
    }
}