Java 8 Streams int和Integer [英] Java 8 Streams int and Integer

问题描述

只是让Java 8弄脏了我，偶然发现了以下行为-

Was just getting my hands dirty with Java 8 and stumbled on a behaviour as below -

public static void main(String... args){
    System.out.println("[Start]");
    int[] ints = {1, 2, 3, 4};
    Stream.of(ints).forEach(i->System.out.println("Int : "+i));


    Integer[] integerNums = {1, 2, 3, 4};
    Stream.of(integerNums).forEach(i->System.out.println("Integer : "+i));

    System.out.println("[End]");
}

输出为:

[Start]
Int : [I@5acf9800
Integer : 1
Integer : 2
Integer : 3
Integer : 4
[End]

我希望代码在两种情况下都能打印所有int和Integer吗?任何对此的见解都将非常有帮助...

Whereas I was expecting the code to print all int's and Integer's in both the cases? Any insights on this would be greatly helpful...

推荐答案

泛型不适用于原始类型. Stream.of 方法声明为

Generics don't work with primitive types. The Stream.of method is declared as

static <T> Stream<T> of(T... values)

使用时

Stream.of(ints)

其中 ints 是一个 int [] ，Java没有看到许多 int 元素(原始类型)，它看到了一个单个 int [] 元素(引用类型).因此，单个 int [] 被绑定为由 T ... values 表示的数组中的唯一元素.

where ints is an int[], Java doesn't see a number of int elements (primitive types), it sees a single int[] element (which is a reference type). So the single int[] is bound as the only element in the array represented by T... values.

因此， values 成为 int [] [] ，其每个元素都是 int [] ，其打印效果类似于

So values becomes an int[][] and each of its elements is an int[], which print like

[I@5acf9800

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