CODEWITHSUNDEEP
java
Prashant
Prashant

Reputation: 5423

Infinity is equal to Infinity in Java

I wanted to test if infinity is equal to infinity in Java:

Double.POSITIVE_INFINITY == Double.POSITIVE_INFINITY

I was surprised by the result when it turned out to be true. My question is how can two infinite values be equal?

Upvotes: 1

Views: 2570

Answers (1)

Andy Turner
Andy Turner

Reputation: 140544

Because Double.POSITIVE_INFINITY represents a specific number, so comparing it to itself using == should return true.

This behaviour is specified explicitly in JLS Sec 15.21.1:

Floating-point equality testing is performed in accordance with the rules of the IEEE 754 standard:

  • ...

  • Otherwise, two distinct floating-point values are considered unequal by the equality operators.

    In particular, there is one value representing positive infinity and one value representing negative infinity; each compares equal only to itself, and each compares unequal to all other values.

Upvotes: 8

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