How to implement infinity in Java?

Does Java have anything to represent infinity for every numerical data type? How is it implemented such that I can do mathematical operations with it?

E.g.

int myInf = infinity; //However it is done
myInf + 5; //returns infinity
myInf*(-1); //returns negative infinity

I have tried using very large numbers, but I want a proper, easy solution.

Solution 1:

double supports Infinity

double inf = Double.POSITIVE_INFINITY;
System.out.println(inf + 5);
System.out.println(inf - inf); // same as Double.NaN
System.out.println(inf * -1); // same as Double.NEGATIVE_INFINITY

prints

Infinity
NaN
-Infinity

note: Infinity - Infinity is Not A Number.

Solution 2:

I'm supposing you're using integer math for a reason. If so, you can get a result that's functionally nearly the same as POSITIVE_INFINITY by using the MAX_VALUE field of the Integer class:

Integer myInf = Integer.MAX_VALUE;

(And for NEGATIVE_INFINITY you could use MIN_VALUE.) There will of course be some functional differences, e.g., when comparing myInf to a value that happens to be MAX_VALUE: clearly this number isn't less than myInf. Also, as noted in the comments below, incrementing positive infinity will wrap you back around to negative numbers (and decrementing negative infinity will wrap you back to positive).

There's also a library that actually has fields POSITIVE_INFINITY and NEGATIVE_INFINITY, but they are really just new names for MAX_VALUE and MIN_VALUE.

Solution 3:

To use Infinity, you can use Double which supports Infinity: -

    System.out.println(Double.POSITIVE_INFINITY);
    System.out.println(Double.POSITIVE_INFINITY * -1);
    System.out.println(Double.NEGATIVE_INFINITY);

    System.out.println(Double.POSITIVE_INFINITY - Double.NEGATIVE_INFINITY);
    System.out.println(Double.POSITIVE_INFINITY - Double.POSITIVE_INFINITY);

OUTPUT: -

Infinity
-Infinity
-Infinity

Infinity 
NaN

Solution 4:

The Double and Float types have the POSITIVE_INFINITY constant.

Solution 5:

I'm not sure that Java has infinity for every numerical type but for some numerical data types the answer is positive:

Float.POSITIVE_INFINITY
Float.NEGATIVE_INFINITY

Double.POSITIVE_INFINITY
Double.NEGATIVE_INFINITY

Also you may find useful the following article which represents some mathematical operations involving +/- infinity: Java Floating-Point Number Intricacies.