Consumer<T> 消费型接口

void accept(T t)

@Test
public void consumer1() {
    happy(10000, (m) -> System.out.println("消费" + m + "元"));
}

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

Supplier<T> 供给型接口

T get()

@Test
public void supplier1() {
    List<Integer> numList = getNumList(() -> (int) (Math.random() * 100));
    numList.forEach(num -> System.out.println(num));
}

public List<Integer> getNumList(Supplier<Integer> supplier) {
    List<Integer> list = new ArrayList<>();
    for (int i = 0; i < 10; i++) {
        list.add(supplier.get());
    }
    return list;
}

Function<T,R> 函数型接口

R apply(T t)

@Test
public void function1() {
    int length = getLength("baozi", (str) -> str.length());
    System.out.println(length);
}

public Integer getLength(String str, Function<String, Integer> function) {
    Integer length = function.apply(str);
    return length;
}

Predicate<T> 断言型接口

boolean test(T t)

@Test
public void predicate1() {
    List<String> list = Arrays.asList("Hello", "atguigu", "Lambda", "www", "ok");
    List<String> result = filterStr(list, (str) -> str.length() > 3);
    result.forEach(r -> System.out.println(r));
}

public List<String> filterStr(List<String> list, Predicate<String> predicate) {
    List<String> strs = new ArrayList<>();
    list.forEach(str -> {
        if (predicate.test(str)) {
            strs.add(str);
        }
    });
    return strs;
}