java8中内置的四大核心函数式接口Consumer<T>：消费型接口

void accept(T t)

//Consumer<T> 消费型接口 public void happy(double money, Consumer<Double> con){ con.accept(money); }Supplier<T>：供给型接口

T get();

//Supplier<T> 供给型接口 //需求：产生一些整数，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; } @Test public void test2(){ List<Integer> numList = getNumList(10, () -> (int)(Math.random() * 100)); for (Integer num : numList){ System.out.println(num); } }Function<T, R>：函数型接口

R apply(T t);

//Function<T, R> 函数型接口 //需求：用于处理字符串 public String strHandler(String str, Function<String, String> fun){ return fun.apply(str); } @Test public void test3(){ String newStr = strHandler("\t\t\t e路纵横开发团队", (str) -> str.trim()); System.out.println(newStr); String subStr = strHandler("e路纵横开发团队", (str) -> str.substring(0, 4)); System.out.println(subStr); }Predicate<T>：断言型接口

boolean test(T t);

//Predicate<T> 断言型接口 //需求：将满足条件的字符串，放入集合中去 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; } @Test public void test4(){ List<String> list = Arrays.asList("Hello", "e路纵横", "Lambda", "ok"); List<String> strList = filterStr(list, (s) -> s.length() > 3); for (String str : strList){ System.out.println(str); } }