使用函數(shù)式接口
Predicate
@FunctionalInterface
interface Predicate<T>{
boolean test(T t);
}
public static <T> List<T> filter(List<T> list,Predicate<T> p){
List<T> ts = new ArrayList<>();
for (T t : list) {
if (p.test(t)) {
ts.add(t);
}
}
return ts;
}
Consumer
@FunctionalInterface
public interface Consumer<T> {
void accept(T t);
}
public static <T> void forEach(List<T> list,Consumer<T> c) {
for (T t : list) {
c.accept(t);
}
}
public static void main(String[] args) {
forEach(Arrays.asList(1,2,3,4,5),i-> System.out.println(i));
}
Function
@FunctionalInterface
public interface Function<T, R> {
R apply(T t);
}
public static <T, R> List<R> map(List<T> list, Function<T, R> f) {
List<R> result = new ArrayList<>();
for (T t : list) {
result.add(f.apply(t));
}
return result;
}
public static void main(String[] args) {
List<Integer> map = map(Arrays.asList("lambdas", "in", "action"), s -> s.length());
System.out.println(map);
}
Lambdas及函數(shù)式接口的例子
例子 對應(yīng)接口
布爾表達(dá)式: (List<String> list) -> list.isEmpty() Predicate<List<String>>
創(chuàng)建對象: () -> new Apple(10) Supplier<Apple>
消費一個對象:(Apple a) ->
System.out.println(a.getWeight()); Consumer<Apple>
從一個對象中選擇/提取:(String s )->s.length() Function<String,Integer>或
ToIntFunction<String>
合并兩個值:(int a, int b)->a*b IntBinaryOperator
比較兩個對象:(Apple a1,Apple a2)-> BiFunction<Apple,Apple,Integeer>
a1.getWeight().compareTo(a2.getWeight()) 或ToIntBiFunction<Apple,Apple>
