Stream流、方法引用

Stream流

Stream流定义

对数组、集合或其他进行流式处理的一个接口，是目前Lambda表达式的使用者之一。

Stream流的使用

 public static void main(String[] args) {
        List<Camel> stream01 = new ArrayList<Camel>() {
            {
                //元素序列-----翻译过来就是集合中的所有元素对象
                add(new Camel("Elsdon", "Jaycob", "Java programmer", "male", 2000, 18));
                add(new Camel("Tamsen", "Brittany", "Java programmer", "female", 2371, 55));
                add(new Camel("Floyd", "Donny", "Java programmer", "male", 3322, 25));
                add(new Camel("Sindy", "Jonie", "Java programmer", "female", 35020, 15));
                add(new Camel("Vere", "Hervey", "Java programmer", "male", 2272, 25));
                add(new Camel("Maude", "Jaimie", "Java programmer", "female", 2057, 87));
                add(new Camel("Shawn", "Randall", "Java programmer", "male", 3120, 99));
                add(new Camel("Jayden", "Corrina", "Java programmer", "female", 345, 25));
                add(new Camel("Palmer", "Dene", "Java programmer", "male", 3375, 14));
                add(new Camel("Addison", "Pam", "Java programmer", "female", 3426, 20));
            }
        };
        List<Camel> stream02 = new ArrayList<Camel>() {
            {
                //元素序列-----翻译过来就是集合中的所有元素对象
                add(new Camel("Elsdon", "Jaycob", "Java programmer", "male", 2000, 18));
                add(new Camel("Tamsen", "Brittany", "Java programmer", "female", 2371, 55));
                add(new Camel("Floyd", "Donny", "Java programmer", "male", 3322, 25));
                add(new Camel("Sindy", "Jonie", "Java programmer", "female", 35020, 15));
                add(new Camel("Vere", "Hervey", "Java programmer", "male", 2272, 25));
                add(new Camel("Maude", "Jaimie", "Java programmer", "female", 2057, 87));
                add(new Camel("Shawn", "Randall", "Java programmer", "male", 3120, 99));
                add(new Camel("Jayden", "Corrina", "Java programmer", "female", 345, 25));
                add(new Camel("Palmer", "Dene", "Java programmer", "male", 3375, 14));
                add(new Camel("Addison", "Pam", "Java programmer", "female", 3426, 20));
            }
        };

        List<String> listCollect = stream01.
                //filter创建流对象
                stream()
                //filter进行过滤，获取年龄大于30岁的动物
                .filter(e -> e.getAge() > 30).
                //filter进行类型转换，将动物对象转为动物的所有名字
                        map(e -> e.getName()).
                //filter进行终端操作，流转换，将流转换为List集合
                        collect(Collectors.toList());
        long count = listCollect.
                //filter创建流对象
                stream().
                //filter进行跳跃,跳过前两个元素
                skip(2).
                //filter对流进行截取,只取用前3个
                limit(3).
                //filter对流进行统计,统计其元素个数
                count();
        listCollect.
                //filter创建流对象
                stream().
                //filter进行迭代，最后进行打印，这里迭代为内部迭代(他帮你实现迭代逻辑);iterator为外部迭代
                forEach(System.out::println);
        //将两个流对象进行拼接组合
        Stream.concat(stream02.stream(),stream01.stream());
    }

方法引用

方法引用定义

双冒号::为引用运算符，而它所在的表达式被称为方法引用。Lambda要表达的函数方案已经存在于某个方法的实现中，那么则可以通过双冒号来引用该方法作为Lambda的替代者，是Lambda表达式的升级者。

方法引用的使用

//函数式接口
public interface Printable {

    void print(String message);

}
    public static void main(String[] args) {
       //使用方法引用 System.out 对象存在  println方法也存在
        print("HelloWorld", System.out::println);
    }
    /**
     * @author  zhuyang
     * @description 使用函数式接口作为方法的参数
     * @date 2021-04-18 19:44 
     * @param message: 
     * @param printable:   
     */
    public static void print(String message,Printable printable){
        printable.print(message);
    }

Gitee地址

Stream流：https://gitee.com/zhuayng/foundation-study/tree/develop/JavaBasis/Other/src/main/java/com/yxkj/other/modular/lambda/stream
方法引用: https://gitee.com/zhuayng/foundation-study/tree/develop/JavaBasis/Other/src/main/java/com/yxkj/other/modular/lambda/quote

总结

匿名内部类和函数式接口为Lambda铺路，Stream流作为Lambda的现实使用者，方法引用则简化Lambda表达式，作为Lambda表达式的终极版本。