|
BiFunction<Function<T,K>, BiFunction<S,T,R>, List<R>> join(List<T> destList, Map<K,S> srcMap) {
return (dkeyFunc,mergeFunc) -> destList.stream().map(
dest -> {
K key = dkeyFunc.apply(dest);
S src = srcMap.get(key);
return mergeFunc.apply(src, dest);
}).collect(Collectors.toList());
}
/** 对给定的值 x,y 应用指定的二元操作函数 */
public static <T,S,R> Function<BiFunction<T,S,R>, R> op(T x, S y) {
return opFunc -> opFunc.apply(x, y);
}
/** 将两个函数使用组合成一个函数，这个函数接受一个二元操作函数 */
public static <T,S,Q,R> Function<BiFunction<S,Q,R>, R> op(Function<T,S> funcx, Function<T,Q> funcy, T x) {
return opFunc -> opFunc.apply(funcx.apply(x), funcy.apply(x));
}
public static <T,S,Q,R> Function<BiFunction<S,Q,R>, Function<T,R>> op(Function<T,S> funcx, Function<T,Q> funcy) {
return opFunc -> aT -> opFunc.apply(funcx.apply(aT), funcy.apply(aT));
}
/** 将两个函数组合成一个叠加函数, compose(f,g) = f(g) */
public static <T> Function<T, T> compose(Function<T,T> funcx, Function<T,T> funcy) {
return x -> funcx.apply(funcy.apply(x));
}
/** 将若干个函数组合成一个叠加函数, compose(f1,f2,...fn) = f1(f2(...(fn))) */
public static <T> Function<T, T> compose(Function<T,T>... extraFuncs) {
if (extraFuncs == null || extraFuncs.length == 0) {
return x->x;
}
return x -> Arrays.stream(extraFuncs).reduce(y->y, FunctionUtil::compose).apply(x);
}
public static void main(String[] args) {
System.out.println(multiGetResult(
Arrays.asList(
list -> list.stream().collect(Collectors.summarizingInt(x->x)),
list -> list.stream().filter(x -> x < 50).sorted().collect(Collectors.toList()),
list -> list.stream().collect(Collectors.groupingBy(x->(x%2==0? "even": "odd"))),
list -> list.stream().sorted().collect(Collectors.toList()),
list -> list.stream().sorted().map(Math::sqrt).collect(Collectors.toMap(x->x, y->Math.pow(2,y)))),
Arrays.asList(64,49,25,16,9,4,1,81,36)));
List<Integer> list = Arrays.asList(1,2,3,4,5);
Supplier<Map<Integer,Integer>> mapSupplier = () -> list.stream().collect(Collectors.toMap(x->x, y-> y * y));
Map<Integer, Integer> mapValueAdd = list.stream().collect(Collectors.toMap(x->x, y->y, (v1,v2) -> v1+v2, mapSupplier));
System.out.println(mapValueAdd);
List<Integer> nums = Arrays.asList(Arrays.asList(1,2,3), Arrays.asList(1,4,9), Arrays.asList(1,8,27))
.stream().flatMap(x -> x.stream()).collect(Collectors.toList());
System.out.println(nums);
List<Integer> fibo = Arrays.asList(1,2,3,4,5,6,7,8,9,10).stream().collect(new FiboCollector());
System.out.println(fibo);
System.out.println(op(new Integer(3), Integer.valueOf(3)).apply((x,y) -> x.equals(y.toString())));
System.out.println(op(x-> x.length(), y-> y+",world", "hello").apply((x,y) -> x+" " +y));
System.out.println(op(x-> x, y-> y+",world").apply((x,y) -> x+" " +y).apply("hello"));
System.out.println(op(x-&g |