减少 int[] 数组时出现“错误：找不到适合减少的方法”

如何解决减少 int[] 数组时出现“错误：找不到适合减少的方法”

鉴于此尝试实现总和：

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提供给编译器进行类型推断的类型信息不足。但是这里我们有一个明确的 int[] 数组作为源。为什么会发生此错误？

Line 3: error: no suitable method found for reduce(int,b)->a + b)
        var sum = Arrays.asList(nums).stream().reduce(0,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,? super T,BinaryOperator<U>)
    T extends Object declared in interface Stream

解决方法

var sum = Arrays.asList(nums) 返回一个List，因此reduce 方法将int[] 添加到int[]，这是不允许的，会导致编译错误。

这是一个可能的解决方案：

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

或

var result = Arrays.stream(nums).sum();