java8中内置的四大核心函数式接口

Posted 2021-11-27

java8中内置的四大核心函数式接口

Consumer<T>：消费型接口

void accept(T t)

 //Consumer<T> 消费型接口
    public void happy(double money, Consumer<Double> con){
        con.accept(money);
    }

Supplier<T>：供给型接口

T get();

//Supplier<T> 供给型接口
    //需求：产生一些整数，并放入集合中
    public List<Integer> getNumList(int num, Supplier<Integer> sup){
        List<Integer> list = new ArrayList<>();

        for (int i = 0; i < num; i++){
            Integer n = sup.get();
            list.add(n);
        }
        return list;
    }

    @Test
    public void test2(){
        List<Integer> numList = getNumList(10, () -> (int)(Math.random() * 100));

        for (Integer num : numList){
            System.out.println(num);
        }
    }

Function<T, R>：函数型接口

R apply(T t);

//Function<T, R> 函数型接口
    //需求：用于处理字符串
    public String strHandler(String str, Function<String, String> fun){
        return fun.apply(str);
    }

    @Test
    public void test3(){
        String newStr = strHandler("\t\t\t e路纵横开发团队", (str) -> str.trim());
        System.out.println(newStr);

        String subStr = strHandler("e路纵横开发团队", (str) -> str.substring(0, 4));
        System.out.println(subStr);
    }

Predicate<T>：断言型接口

boolean test(T t);

//Predicate<T> 断言型接口
    //需求：将满足条件的字符串，放入集合中去
    public List<String> filterStr(List<String> list, Predicate<String> pre){
        List<String> strList = new ArrayList<>();

        for (String str : list){
            if (pre.test(str)){
                strList.add(str);
            }
        }
        return strList;
    }

    @Test
    public void test4(){
        List<String> list = Arrays.asList("Hello", "e路纵横", "Lambda", "ok");
        List<String> strList = filterStr(list, (s) -> s.length() > 3);

        for (String str : strList){
            System.out.println(str);
        }
    }