在Java中将变量直接分配给包装器类是一种好习惯吗？

Question

As I am slowly progressing through the java tutorials, I came across java helper classes. The code is

public static void main(String args[]) {
char myLittleChar = 'b';
char myBigChar = Character.toUpperCase(myLittleChar);
System.out.println(myBigChar);

However, it worked the same even when assigning directly to a helper class.

Character c = 'a';
System.out.println(c.toUpperCase(c));

and the same applied for short or float as well.

However, I didn't come across this much in any tutorial, or any sample code, and is declared as int , short etc. Is it considered a bad practice? If so, why?

Thank you.

Answer 1

Character wraps the primitive two-byte char in an object. That is superfluous. You could write

char myBigChar = Character.toUpperCase('b');

So it is a matter of efficiency.

By the way String already is an object, and does not have this verbosity.

Answer 2

If I understand what you're asking, you want to know the utility ot wrapper Object classes versus their primitive counterparts.

There are many advantages to wrapper classes:

• They can be used as generic types
• They are nullable
• They provide utility methods on their wrapped primitive value and other static methods
• etc.

On the other side of your question, there's a concept called boxing / unboxing.

When you: Character c = 'a'; , you are autoboxing primitive value 'a' into its wrapper Character class.

If you follow that assignment with something like: char a = c; , you are automatically unboxing the wrapper's value into its primitive counterpart.