Integer value comparison
Solution 1
Integers are autounboxed, so you can just do
if (count > 0) {
....
}
Solution 2
To figure out if an Integer
is greater than 0, you can:
-
check if
compareTo(O)
returns a positive number:if (count.compareTo(0) > 0) ...
But that looks pretty silly, doesn't it? Better just...
-
use autoboxing1:
if (count > 0) ....
This is equivalent to:
if (count.intValue() > 0) ...
It is important to note that "
==
" is evaluated like this, with theInteger
operand unboxed rather than theint
operand boxed. Otherwise,count == 0
would return false whencount
was initialized asnew Integer(0)
(because "==
" tests for reference equality).
1Technically, the first example uses autoboxing (before Java 1.5 you couldn't pass an int
to compareTo
) and the second example uses unboxing. The combined feature is often simply called "autoboxing" for short, which is often then extended into calling both types of conversions "autoboxing". I apologize for my lax usage of terminology.
Solution 3
It's better to avoid unnecessary autoboxing for 2 reasons.
For one thing, it's a bit slower than int < int
, as you're (sometimes) creating an extra object;
void doSomethingWith(Integer integerObject){ ...
int i = 1000;
doSomethingWith(i);//gets compiled into doSomethingWith(Integer.valueOf(i));
The bigger issue is that hidden autoboxing can hide exceptions:
void doSomethingWith (Integer count){
if (count>0) // gets compiled into count.intValue()>0
Calling this method with null
will throw a NullPointerException
.
The split between primitives and wrapper objects in java was always described as a kludge for speed. Autoboxing almost hides this, but not quite - it's cleaner just to keep track of the type. So if you've got an Integer object, you can just call compare()
or intValue()
, and if you've got the primitive just check the value directly.
Solution 4
You can also use equals:
Integer a = 0;
if (a.equals(0)) {
// a == 0
}
which is equivalent to:
if (a.intValue() == 0) {
// a == 0
}
and also:
if (a == 0) {
}
(the Java compiler automatically adds intValue())
Note that autoboxing/autounboxing can introduce a significant overhead (especially inside loops).
Solution 5
Although you could certainly use the compareTo
method on an Integer instance, it's not clear when reading the code, so you should probably avoid doing so.
Java allows you to use autoboxing (see http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html) to compare directly with an int, so you can do:
if (count > 0) { }
And the Integer
instance count
gets automatically converted to an int
for the comparison.
If you're having trouble understanding this, check out the link above, or imagine it's doing this:
if (count.intValue() > 0) { }
phill
Programming server admin stuff with vbscript, python, powershell, php, and c#.
Updated on July 12, 2020Comments
-
phill almost 4 years
I'm a newbie Java coder and I just read a variable of an integer class can be described three different ways in the API. I have the following code:
if (count.compareTo(0)) { System.out.println(out_table); count++; }
This is inside a loop and just outputs
out_table
.
My goal is to figure out how to see if the value in integercount > 0
.I realize the
count.compare(0)
is the correct way? or is itcount.equals(0)
?I know the
count == 0
is incorrect. Is this right? Is there a value comparison operator where its justcount=0
?