Java 通用整数数据与原始整数数据

Question

I know that in Java we can use generic data types for various reasons. However, in terms of data storage . If a primitive int in Java can store up to 2,147,483,647 signed values, does this same storage capacity apply for the Integer generic type? Also, does the data type chosen in a program affect the runtime in any way? Or does it more so affect the space-time complexity of a program? My main question is that if I stick with a data type that is rather small but appropriate for my programs needs, than will it by any means help my program run faster?

Answer 1

Yes, the limitations are still there.

You shouldn't treat Integer like this magical object, all it is is an object that holds an int called value . So, without auto-boxing and unboxing, you could technically create your own Integer wrapper class. What to take away is Integer is pretty much the exact same as int , except it's an object.

About your main question about the speed, Integer is just a tiny bit slower, but I don't think you should worry about it. It's only slower because Objects need to be allocated in the heap space.

Answer 2

Yes, the same limitations apply.

You can see the source of the Integer class here:

http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/687fd7c7986d/src/share/classes/java/lang/Integer.java

Line 840 shows that an Integer is backed by a simple int :

private final int value;

So whatever restrictions an int has, an Integer also has.