Unravel › Java concepts › Numbers and math

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At a glance

1. 1Math.round(2.5) is 3 and Math.round(-2.5) is -2 (it rounds half up toward positive infinity)Math.floor rounds down, Math.ceil rounds up, and both return doubles.
2. 2Math.pow(2, 10) is 1024.0, a double; for integer powers of two, shifts (1 << 10) are exactMath.sqrt(-1) is NaN.
3. 3Math.max(a, b), min and abs are overloaded for int, long, float and doubleUse Math.clamp(value, min, max) (Java 21) to keep a number in a range.
4. 4Ceiling division of integers: (a + b - 1) / b, because Math.ceil(a / b) divides as integers first

• Math.random() returns a double in [0, 1) and is fine for casual use; for tests use a seeded Random, for security use SecureRandom
• Math.abs(Integer.MIN_VALUE) is negative, and Math.round returns long for a double (or int for float), so casting to int can overflow
• Many Math methods are intrinsics: the JIT replaces Math.sqrt or Math.abs with a single CPU instruction

public class Geometry {  static double distance(double x1, double y1, double x2, double y2) {    return Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2));  }  static int pages(int items, int perPage) { return (items + perPage - 1) / perPage; }  static long cents(double euros) { return Math.round(euros * 100); }}

1. line 3 uses Math, the core of Math and number utilities
2. line 6 uses Math, the core of Math and number utilities

How Unravel recognises it

When you paste code, Unravel looks for these signs of math and number utilities. Spotting them yourself is a good habit when you read unfamiliar code:

• Types: Math
• Method calls: Math.sqrt() Math.pow() Math.round() Math.floor() Math.ceil() Math.hypot() Math.log() Math.signum() Math.clamp()

Part of a learning path

• Text, numbers and arrays · previous: Autoboxing and wrapper types · next: Random numbers and UUIDs

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