将Array作为参数传递给{}

Question

I can set an array like this:

Object[] objects = {new Object()};

However if I have a method:

public void setObject(Object[] objects) {

}

I cannot do the following:

setObject({new Object()});

Why is this? Why doesn't {new Object()} suffice as an argument but suffices to initialize an Object[] array?

Answer 1

You can pass an anonymous array :

setObject(new Object[] { new Object() });

Note that the syntax { new Object() } just works when initializing the array on its declaration. For example:

Object[] arr = { new Object() };

This doesn't work after declaring the array:

Object[] arr;
//uncomment below line and you'll get a compiler error
//arr = { new Object() };
arr = new Object[] { new Object() };

Answer 2

Because you haven't typed the Array. It could be objects, integers, whatever.

The following should work:

setObject(new Object[]{new Object()});

Answer 3

适当的回调是：

setObject(new Object[]{new Object()});

Answer 4

Every Java array has a component type. When used in an initializer, the compiler infers that the type of the new array (the right-hand side) is the same as the declared type (the left-hand side).

When the declaration is missing, the compiler doesn't know what the component type of the array should be. You must be explicit, using the expression setObject(new Object[] { new Object() })

One might wonder why the compiler doesn't infer the type from the declared type of the method parameter, like it does when initializing a variable. But, the compiler resolves the method to call based on the parameter types; if you don't know the method you are calling, you can't infer anything from its parameter types. There's no circularity when initializing a variable.