<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);
示例:
public class TestLambda {
//Predicate<T> 断言型接口
@Test
public void testPredicate() {
List<String> list = Arrays.asList("hello", "ad", "www");
List<String> newList = filterStr(list, s -> s.length() >= 3);
newList.forEach(System.out::println);
}
//需求: 将满足条件的字符串添加到集合中
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 testFunction() {
String str = strHandler("\t\t\t hello world", s -> s.trim());
System.out.println(str);
}
//需求: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 testSupplier() {
List<Integer> numList = getNumList(10, () -> (int) (Math.random() * 100));
for (Integer num : numList) {
System.out.println(num);
}
}
//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 = Lists.newArrayList();
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 testConsumer() {
happy(100, con -> System.out.println("刘剑喜欢看电影,每次消费:" + con + "元"));
}
public void happy(double money, Consumer<Double> con) {
con.accept(money);
}
}