JAVA8函數式接口

java8 中內置的四大核心函數接口
*
* Consumer<T> ：消費型接口
*         void accept(T t)
* Supplier<T> :供給型接口
*          T get()
*
* Function<T,R>:函數型接口
*          R apply(T t)
* Predicate<T> :斷言型接口
*          boolean test(T t)

package airycode_java8.nice4;

import org.junit.Test;

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;
import java.util.function.Supplier;

/**
 *
 * java8 中內置的四大核心函數接口
 *
 * Consumer<T> ：消費型接口
 *         void accept(T t)
 * Supplier<T> :供給型接口
 *          T get()
 *
 * Function<T,R>:函數型接口
 *          R apply(T t)
 * Predicate<T> :斷言型接口
 *          boolean test(T t)
 * Created by admin on 2019/1/2.
 */
public class TestLambda {

    @Test
    public void test1(){
        happy(10000,(m)-> System.out.println("大保健，每次消費"+m));
    }

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

    //函數型接口
    @Test
    public void test3(){

        String result = handler("aa", (str) -> str.toUpperCase());
        System.out.println(result);


    }


    //斷言型接口
    @Test
    public void test4(){

        List<String> list = Arrays.asList("Hello","AA","CCCC");
        List<String> resultList = filterStr(list, (str) -> str.length() > 3);
        for (String str:resultList) {
            System.out.println(str);
        }


    }

    //需求：我要將知足條件的字符串放入集合中
    public List<String> filterStr(List<String> list, Predicate<String> pre){
        List<String> result = new ArrayList<>();
        for (String str:list) {
            if (pre.test(str)) {
                result.add(str);
            }
        }
        return result;
    }





    //需求：用於處理字符串
    public String handler(String string, Function<String,String> fun){
        return fun.apply(string);
    }




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

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

}