JAva 8に内蔵された4つのコア関数インタフェース

 //Consumer      
    public void happy(double money, Consumer con){
        con.accept(money);
    }

//Supplier      
    //  ：      ，      
    public List getNumList(int num, Supplier sup){
        List list = new ArrayList<>();

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

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

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

//Function      
    //  ：       
    public String strHandler(String str, Function fun){
        return fun.apply(str);
    }

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

        String subStr = strHandler("e       ", (str) -> str.substring(0, 4));
        System.out.println(subStr);
    }

//Predicate      
    //  ：         ，      
    public List filterStr(List list, Predicate pre){
        List strList = new ArrayList<>();

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

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

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