Java8內置的四大核心函數式接口

package java_8;
    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.Predicate;
    import java.util.function.Supplier;
    import java.util.function.Function;
    /**
     * Java8內置的四大核心函數式接口
     * <p>
     * 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);
     *
     *Java8中還提供了其他函數式接口
     */
    public class TestLambda4 {
        //predicate<T> 斷言型接口:
        @Test
        public void test4(){
            List<String> list = Arrays.asList("Hello","Lambda","Go","java");
            list = filterStr(list, s->s.contains("o"));
            list.forEach(System.out::println);
        }
        //需求:將滿足條件的字符串添加到集合中
        public List<String> filterStr(List<String> list, Predicate<String> predicate) {
            List<String> stringList = new ArrayList<>();
            for (String str : list) {
                if (predicate.test(str))
                    stringList.add(str);
            }
            return stringList;
        }
        //-----------------------------------------------------------
        //Function<T,R>函數型接口
        @Test
        public void test3() {
            String str = strHandler("huangyichun", s -> s.toUpperCase());
            System.out.println(str);
        }
        //需求用於處理字符串
        public String strHandler(String str, Function<String, String> fun) {
            return fun.apply(str);
        }
        //-------------------------------------------------
        //Supplier<T>供給型接口:
        @Test
        public void test2() {
            List<Integer> list = getNumList(10, () -> (int) (Math.random() * 100));
            list.forEach(System.out::println);
        }
        //需求：產生指定個整數，並放入集合中
        public List<Integer> getNumList(int num, Supplier<Integer> sup) {
            List<Integer> list = new ArrayList<>();
            for (int i = 0; i < num; i++) {
                list.add(sup.get());
            }
            return list;
        }
        //-----------------------------------------------------------
        //Consumer<T> 消費型接口
        @Test
        public void test1() {
            happy(10000, m -> System.out.println(m));
        }
        public void happy(double money, Consumer<Double> con) {
            con.accept(money);
        }
    }