Java进阶 - Stream流、方法引用

public class ForStream {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        list.add("林子东");
        list.add("蔡晓武");
        list.add("夏琨");
        list.add("林子成");
        list.add("林峰");
        //对集合进行过滤，要以林开头，且长度为3,最后输出打印
        //首先将集合转换为Stream流
        list.stream()
                //filter参数是predicate接口，可以用lanmda表达式进行判断
                .filter(name -> name.startsWith("林"))
                .filter(name -> name.length()==3)
                //forEach参数是consumer接口，可以消费打印
                .forEach(name-> System.out.println(name));
    }
}

public class GetStream {
    public static void main(String[] args) {
        //list集合
        List<String> list = new ArrayList<>();
        Stream<String> stream1 = list.stream();

        //set集合
        Set<String> set = new HashSet<>();
        Stream<String> stream2 = set.stream();

        //map集合间接调用
        Map<String,String> map = new HashMap<>();

        //获取键，存储到一个set集合中
        Set<String> keySet = map.keySet();
        Stream<String> stream3 = keySet.stream();

        //获取值，存储到Collection集合中
        Collection<String> values = map.values();
        Stream<String> stream4 = values.stream();

        //获取键值对（键与值的映射关系）
        Set<Map.Entry<String, String>> entries = map.entrySet();
        Stream<Map.Entry<String, String>> stream5 = entries.stream();

        //把数组转换为stream流
        Stream<Integer> integerStream = Stream.of(1, 2, 3, 4, 5);
        //可变参数可以传递数组
        Integer[] arr = {1,2,3,4,5};
        Stream<Integer> stream6 = Stream.of(arr);
    }
}

public class NormalMethod {
    public static void main(String[] args) {
        Stream<String> stream = Stream.of("张三丰", "张志杰", "赵敏");
        //进行过滤
        Stream<String> nameList = stream.filter(name -> name.startsWith("张"));
        //遍历输出
        nameList.forEach(name-> System.out.println(name));
    }
}

public class NormalMethod {
    public static void main(String[] args) {
        Stream<String> stream = Stream.of("1", "2", "3");
        //进行转换
        Stream<Integer> integerStream = stream.map(num -> Integer.parseInt(num));
        //遍历输出
        integerStream.forEach(name-> System.out.println(name));
    }
}

接口：
@FunctionalInterface
public interface printable {
    void print(String s);
}
打印类：
public class UpperMethod {
    public void toUp(String s){
        System.out.println(s.toUpperCase());
    }
}
主方法：
public class DemoPrintable {
    public static void main(String[] args) {
        // 先创建对象，通过对象对已存在的方法进行方法引用
        UpperMethod obj = new UpperMethod();
        method(obj::toUp, "ddd");
    }

    public static void method(printable p, String s) {
        p.print(s);
    }
}

method(super::greet)

method（10,int[]::new）;