Variable names in Java should begin with a letter, not include spaces or special characters, use full words instead of abbreviations, and follow conventions for capitalization and underscores depending on whether the variable is a single word or stores a constant value. Correct names include myName, circleRadius, gearRatio and currentGear while incorrect names include 3star, star3, my Name, and r instead of radius.

1. Variable names are case-sensitive.
These two names are different
dogFigo
dogfigo

2. Begin your variable names with a letter
Identify wrong variable names
● 3star
● star3
● abc123

3. White space is not permitted
These are incorrect variable names
● my Name
● circle Radius
These are correct
● myName
● circleRadius

4. Use full words instead of cryptic abbreviations
these are incorrect names
● r instead of radius
● rad instead of radius
● ar instead of area

5. If the name you choose consists of only one word,
spell that word in all lowercase letters

6. for more than one word, capitalize the first letter of each
subsequent word.
e.g;
gearRatio
currentGear

7. If your variable stores a constant value, such as
static final int NUM_GEARS =6
the convention changes slightly, capitalizing every letter and separating
subsequent words with the underscore character. By convention, the
underscore character is never used elsewhere.