考虑到实现求和的尝试：

int[] nums = { 1,3,4,5,7};
var sum = Arrays.asList(nums).stream().reduce(0,(a,b)->a+b);

像下面这样的问题通常是由于没有足够的类型信息提供给编译器进行类型推断。但是这里我们有一个不含糊的int[]数组作为源。为什么会发生这种错误？

Line 3: error: no suitable method found for reduce(int,(a,b)->a + b)
        var sum = Arrays.asList(nums).stream().reduce(0,(a,b)->a+b);
                                              ^
    method Stream.reduce(int[],BinaryOperator<int[]>) is not applicable
      (argument mismatch; int cannot be converted to int[])
    method Stream.<U>reduce(U,BiFunction<U,? super int[],U>,BinaryOperator<U>) is not applicable
      (cannot infer type-variable(s) U
        (actual and formal argument lists differ in length))
  where U,T are type-variables:
    U extends Object declared in method <U>reduce(U,BiFunction<U,? super T,U>,BinaryOperator<U>)
    T extends Object declared in interface Stream