Getting the names of things right is extremely important. It makes a huge difference in readability. Many IDEs support refactoring, and specifically renaming. I will sometimes rename classes several times before I hit on exactly the obvious name. It's worth the effort.
Every name is made from the following characters, starting with a letter:
No names can be the same as a Java keyword (eg, import, if, ...).
| ||This is a legal name. Lowercase implies it's a variable or method.|
| ||This is a different legal name. Uppercase implies it's a class or interface.|
| ||Yet a different legal name. All uppercase implies it's a constant.|
| ||Legal, but multiple words should be camelcase.|
|Better, but camelcase is preferred to _ in Java.|
| ||Good Java style|
| ||ILLEGAL - no blanks in a name|
| ||ILLEGAL - same as the Java keyword|
The conventions for the use of upper- and lowercase is not enforced by compilers, but it is so widely observed, that it should have been. Camelcase is the practice of capitalizing the first letter of successive words in multi-word identifiers. Camelcase is much preferred in the Java community over the use of underscores to separate words, or even worse, no distinction made at word boundaries.