需求,定义⼀个可以使⽤加减乘除的接⼝ 以前需要定义4个⽅法
使⽤Lambda表达式后
@FunctionalInterface
public interface OperFunction<R,T> {
R operator(T t1, T t2);
}
public static void main(String[] args) throws Exception {
System.out.println(operator(20, 5, (Integer x, Integer y) -> {
return x * y;
}));
System.out.println(operator(20, 5, (x, y) -> x + y));
System.out.println(operator(20, 5, (x, y) -> x - y));
System.out.println(operator(20, 5, (x, y) -> x / y));
}
public static Integer operator(Integer x, Integer y,
OperFunction<Integer, Integer> of) {
return of.operator(x, y);
}
Java8 内置的四⼤核⼼函数式接⼝
Consumer<T> : 消费型接⼝:有⼊参,⽆返回值
void accept(T t);
Supplier<T> : 供给型接⼝:⽆⼊参,有返回值
T get();
Function<T, R> : 函数型接⼝:有⼊参,有返回值
R apply(T t);
Predicate<T> : 断⾔型接⼝:有⼊参,有返回值,返回值类型确定是boolean
boolean test(T t);
@FunctionalInterface
public interface Function<T, R> {
/**
* Applies this function to the given argument.
*
* @param t the function argument
* @return the function result
*/
R apply(T t);
}
public class FunctionObj implements Function {
@Override
public Object apply(Object o) {
return o+"经过apply处理拼接上了";
}
}
// 输出⼊参的10倍
Function<Integer, Integer> func = p -> p * 100;
func.apply(100);
@FunctionalInterface
public interface BiFunction<T, U, R> {
R apply(T t, U u);
}
public static void main(String[] args) {
System.out.println(operator(10,21,(a,b)->a+b));
System.out.println(operator(10,2,(a,b)->a-b));
System.out.println(operator(8,4,(a,b)->a*b));
System.out.println(operator(10,2,(a,b)->a/b));
}
public static Integer operator(Integer a, Integer b, BiFunction<Integer,
Integer, Integer> bf) {
return bf.apply(a, b);
}
@FunctionalInterface
public interface Consumer<T> {
void accept(T t);
}
public static void main(String[] args) throws Exception {
Consumer<String> consumer = obj->{
System.out.println(obj);
System.out.println("调⽤短信接⼝发送短信,或者打印⽇志");
};
// sendMsg("8888888",obj->{
// System.out.println(obj);
// System.out.println("调⽤短信接⼝发送短信,或者打印⽇志");
// });
sendMsg("8888888",consumer);
}
public static void sendMsg(String phone,Consumer<String> consumer){
consumer.accept(phone);
}
List<String> list = Arrays.asList("aaa","bbb");
list.forEach(obj->{
//TODO
});
@FunctionalInterface
public interface Supplier<T> {
T get();
}
public static void main(String[] args) {
//Student student = new Student();
Student student = newStudent();
System.out.println(student.getName());
}
public static Student newStudent(){
Supplier<Student> supplier = ()-> {
Student student = new Student();
student.setName("默认名称");
return student;
};
return supplier.get();
}
class Student{
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
@FunctionalInterface
public interface Predicate<T> {
boolean test(T t);
}
public static void main(String[] args) {
List<String> list =
Arrays.asList("awewrwe","vdssdsd","aoooo","psdddsd");
List<String> results = filter(list,obj->obj.startsWith("a"));
System.out.println(results);
}
public static List<String> filter(List<String> list,
Predicate<String> predicate) {
List<String> results = new ArrayList<>();
for (String str : list) {
if (predicate.test(str)) {
results.add(str);
}
}
return results;
}