Java8 Lambda expression of the new features (c)

java8中内置的四大核心函数式接口 
1.Consumer<T>：消费型接口(带泛型的接口)，有参数，无返回值
                void accept(T t);
2.Supplier<T>：供给型接口，无参数，有返回值
                T get();
3.Function<T,R>：函数型接口
                R apply(T t);
4.Predicate<T>：断言型接口
                boolean test(T t);

 

package lambda;

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;

public class TestLambda3 {

    //消费型接口
    @Test
    public void test1() {
        happy(1000, m -> System.out.println("买化妆品消费" + m + "元"));
    }

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


    //供给型接口
    @Test
    public void test2() {
        List<Integer> result = getNumberList(10, () -> (int) (Math.random() * 100));
        for (Integer integer : result) {
            System.out.println(integer);
        }
    }

    //产生指定个数的整数(100以内)，并将他们放到集合中去
    public List<Integer> getNumberList(int num, Supplier<Integer> supplier) {
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < num; i++) {
            Integer temp = supplier.get();
            list.add(temp);
        }
        return list;
    }


    //函数型接口
    //用于处理字符串
    @Test
    public void test3() {
        System.out.println(strHandler("today", str -> str.toUpperCase()));
    }

    public String strHandler(String str, Function<String, String> function) {
        return function.apply(str);
    }

    //断言型接口
    @Test
    public void test4() {
        List<String> strList = Arrays.asList("asgdigasi", "shdih", "xs", "hdshasd", "c");
        List<String> list = filterList(strList, (x) -> x.length() > 3);
        for (String s : list) {
            System.out.println(s);
        }
    }

    //将满足条件的字符串放到集合中去
    public List<String> filterList(List<String> strList, Predicate<String> predicate) {
        List<String> list = new ArrayList<>();
        for (String s : strList) {
            if(predicate.test(s)){
                list.add(s);
            }
        }
    return list;
    }

}