package com.brianway.learning.java8.lambda;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import java.util.function.Consumer;

import java.util.function.Function;

import java.util.function.Predicate;

/**

* Created by brian on 17/2/27.

* Java 8 中常用函数式接口

*/

public class FunctionDescriptor {

public static void main(String[] args) {

//使用 Predicate

Predicate<String> nonEmptyStringPredicate = (String s) -> !s.isEmpty();

List<String> listOfStrings = Arrays.asList("aaa", "ss", "");

List<String> nonEmpty = filter(listOfStrings, nonEmptyStringPredicate);

System.out.println("nonEmpty.size() == 2 " + (nonEmpty.size() == 2));

//使用 Consumer

forEach(Arrays.asList(1, 2, 3, 4, 5), System.out::println);

//使用 Function

List<Integer> lengthsOfWord = map(

Arrays.asList("lambda", "in", "action"),

String::length

);

forEach(lengthsOfWord, System.out::println);

}

/**

* 使用 Predicate

*/

public static <T> List<T> filter(List<T> list, Predicate<T> p) {

List<T> results = new ArrayList<>();

//TODO

for (T s : list) {

if (p.test(s)) {

results.add(s);

}

}

return results;

}

/**

* 使用 Consumer

*/

public static <T> void forEach(List<T> list, Consumer<T> c) {

//TODO

for (T i : list) {

c.accept(i);

}

}

/**

* 使用 Function

*/

public static <T, R> List<R> map(List<T> list, Function<T, R> f) {

List<R> result = new ArrayList<>();

//TODO

for (T s : list) {

result.add(f.apply(s));

}

return result;

}

}