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Constants

A constant is a variable that's value cannot be changed once it is assigned. It's basically a value that is "set in stone" and cannot be modified while the code is running.

constant-dino

Why use Constants?​

Constants are used to prevent hard-coding values. For example, imagine having a gear ratio hard coded in 20 different places across your codebase. Then, if you need to change the gear ratio, you need to change it 20 different times. That's why constants are used: to "hard code" values, but only in one spot. Using a constant instead a regular variable also prevents accidentally changing the value.

Creating a Constant​

Constants in java are created by using the final keyword.

Constant Formula​

The general formula for creating a constant is:

final [data type] [constant name] = [value];
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More Keywords​

Typically, constants are also created with the static keyword, so that they can be accessed globally without needing to create an "instance" of the class every time.

For example, you can access Math.PI without writing Math math1 = new Math(); first.

For more information about keywords and variable scope, see the object oriented programming section.

Naming Conventions​

  • Constants should be written in uppercase with words separated by underscores: ROLLER_SLOW_VOLTAGE instead of rollerSlowVoltage
  • Constants should have units in the name: MAX_VELOCITY_METERS_PER_SECOND instead of MAX_VELOCITY