range : Java Glossary

• Converting a random number 0 <= r < 1 to select a weighted quotation.
• Deciding which unit of measure to use depending on its size, e.g. cup, pint, quart, gallon
• Deciding which rule to use for inserting dashes in a ISBN (International Standard Book Number) depending on which band/range it falls into.
• Naming colours given the RGB (Red Green Blue)
• Assigning elements to paint to clipregion bands.
• Converting frequency of light to RGB.
• UTF-8 encoding where characters in different ranges/bands are encoded differently.
• Converting weight, height etc to evaluation words, e.g. fat, very fat
• Calculations with coins.
• Displaying a wide range of numbers or currency values where different ranges are displayed to different precision.

Techniques for searching a list of ranges to find the one a given values falls in:

• Linear search
• Nested if
• binary search
• SQL (Standard Query Language) database. Let it figure it out using indexes on the low and high values.

Often your ranges are all the same length. Then you can find the slot by dividing your value by the range length. This is very fast.

If the length of each range is a multiple of some unit, you can construct a lookup table. You take your value, divide by the length of the unit, and use it to index the table to give you the band number. This is very fast. This technique can be used to deal with weighted values that behave like extending the length of the associated band.

If your ranges are short, and sparse, you can index the start point, rounded, in a HashMap or TreeMap. There is no built-in Collection that will look up ranges for you. You must roll your own.