java - 为什么会出现这种情况下拆箱的情况呢？

Question

根据Java Tutorial ，

Converting an object of a wrapper type (Integer) to its corresponding primitive (int) value is called unboxing. The Java compiler applies unboxing when an object of a wrapper class is:

• Passed as a parameter to a method that expects a value of the corresponding primitive type.
• Assigned to a variable of the corresponding primitive type.

为什么会发生这种情况下的拆箱？

char l = 0;
int arr[] = new int[]{1,2,3};
System.out.println(arr[new Integer(1)]);

在这种情况下，这些事情会在哪里发生？是否有管理数组中元素访问的底层方法？或者 [] 是否暗示某种变量？

Answer 1

JLS 15, §15.10.3关于这一点非常清楚:

...

The index expression undergoes unary numeric promotion (§5.6). The promoted type must be int, or a compile-time error occurs.

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类似的段落可以在旧的 JLS 中找到，例如JLS 8, §15.10.3 .