JAVA四大内置函数

/**
 * Consumer<T> : 消费型接口
 * void accept(T t);
 *
 * Supplier<T> : 供给型接口
 * T get();
 *
 * Function<T, R> : 函数型接口
 * R apply(T t);
 *
 * Predicate<T> : 断言型接口
 * boolean test(T t);
 *
 *
 */

    @Test
    public void test1() {
        happy(10000,x -> System.out.println("喜欢大保健,每次消费"+ x));
        happy(10000,x -> {
            double a = x*100;
        });
    }

    public void happy(double money, Consumer<Double> con) {
        con.accept(money);
    }

test1结果：

 

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//Supplier<T> 供给型接口：
    @Test
    public void test2(){ List<Integer> numList = getNumList(10,() -> (int)(Math.random()*100)); for(Integer num : numList) { System.out.println(num); } } //需求：产生指定个数的整数，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; }

 test2结果：

 

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//Function<T, R> 函数式接口
    @Test
    public void test3() { Integer num = strHandler("123",(x) -> Integer.valueOf(x) +10000); System.out.println(num); } //用于处理字符串 public Integer strHandler(String str, Function<String,Integer> fun) { return fun.apply(str); }

 test3结果：

 

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//Predicate<T> 断言型接口
    @Test
    public void test4() { List<String> list = Arrays.asList("helloww","www","abcdefg","ss","youyiku"); List<String> strings = filterStr(list, (x) -> x.length() > 3); for(String s: strings) { System.out.println(s); } } //需求，将满足条件的字符串，放入集合中 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 4结果：