“Object [] x”和“Object x []”之间有什么区别吗？

Question

I was updating a legacy code base in Java and I found a line like this:

Object arg[] = { new Integer(20), new Integer(22) };

That line catched my attention because I am used to this kind of code:

Object[] arg = { new Integer(20), new Integer(22) };

The content of the array isn't important here. I'm curious about the brackets next to the variable name versus the brackets next to the class name. I tried in Eclipse (with Java 5) and both lines are valid for the compiler.

Is there any difference between those declarations?

Answer 1

Both are legal and both work. But placing [] before the array's name is recommended.

From Javadocs :

You can also place the square brackets after the array's name:

float anArrayOfFloats[]; // this form is discouraged

However, convention discourages this form; the brackets identify the array type and should appear with the type designation.

Answer 2

No, they both work. But watch out:

float anArrayOfFloats[], aSecondVariable;

will declare one array of floats and one float, while:

float[] anArrayOfFloats, aSecondVariable;

will declare two arrays of floats.

Answer 3

There is no difference. Both are legal.

You can read in Java Language Specification http://java.sun.com/docs/books/jls/second_edition/html/arrays.doc.html

The [] may appear as part of the type at the beginning of the declaration, or as part of the declarator for a particular variable, or both, as in this example:

 byte[] rowvector, colvector, matrix[]; 

Answer 4

Another good reason to write Integer[] ints instead of Integer ints[] is because of inheritance relations: Integer[] is subtype of Number[] is subtype of Object[] .

In other words, you can put Integers in an Object array, so you can think of the [] as part of the object's type definition -- which is why it makes sense to have it close to the type instead of the object name.

Answer 5

简答：不。