Java8新特性：Lambda四大核心接口示例

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;

import org.junit.Test;

/*
 * Java8 内置的四大核心函数式接口
 * 
 * Consumer<T> : 消费型接口
 *              void accept(T t);
 * 
 * Supplier<T> : 供给型接口
 *              T get(); 
 * 
 * Function<T, R> : 函数型接口
 *              R apply(T t);
 * 
 * Predicate<T> : 断言型接口
 *              boolean test(T t);
 * 
 */
public class TestLambda3 {
        
        //Predicate<T> 断言型接口：
        @Test
        public void test4(){
                List<String> list = Arrays.asList("Hello", "atguigu", "Lambda", "www", "ok");
                List<String> strList = filterStr(list, (s) -> s.length() > 3);
                
                for (String str : strList) {
                        System.out.println(str);
                }
        }
        
        //需求：将满足条件的字符串，放入集合中
        public List<String> filterStr(List<String> list, Predicate<String> pre){
                List<String> strList = new ArrayList<>();
                
                for (String str : list) {
                        if(pre.test(str)){
                                strList.add(str);
                        }
                }
                
                return strList;
        }
        
        //Function<T, R> 函数型接口：
        @Test
        public void test3(){
                String newStr = strHandler("\t\t\t 这里是去前后空格的   ", (str) -> str.trim());
                System.out.println(newStr);
                
                String subStr = strHandler("这里是截取字符串的", (str) -> str.substring(3, 8));
                System.out.println(subStr);
        }
        
        //需求：用于处理字符串
        public String strHandler(String str, Function<String, String> fun){
                return fun.apply(str);
        }
        
        //Supplier<T> 供给型接口 :
        @Test
        public void test2(){
                List<Integer> numList = getNumList(10, () -> (int)(Math.random() * 100));
                
                for (Integer num : numList) {
                        System.out.println(num);
                }
        }
        
        //需求：产生指定个数的整数，并放入集合中
        public List<Integer> getNumList(int num, Supplier<Integer> sup){
                List<Integer> list = new ArrayList<>();
                
                for (int i = 0; i < num; i++) {
                        Integer n = sup.get();
                        list.add(n);
                }
                
                return list;
        }
        
        //Consumer<T> 消费型接口 :
        @Test
        public void test1(){
                happy(10000, (m) -> System.out.println("小明喜欢购物，每次消费：" + m + "元"));
        } 
        
        public void happy(double money, Consumer<Double> con){
                con.accept(money);
        }
}