Introduction to Java Programming - Building Java Programs: A Back to Basics Approach - page 18

Because this fourth statement is a println command, it finishes the output line
and positions the cursor at the beginning of the second line. The next statement is
another print that produces this:

To be or not to be.That is the question.
This is
^

The final println completes the second line and positions the output cursor at the
beginning of a new line:

To be or not to be.That is the question.
This is for the whole family!

^

These six statements are equivalent to the following two single statements:

System.out.println("To be or not to be.That is the question.");
System.out.println("This is for the whole family!");

Using the print and println commands together to produce lines like these may
seem a bit silly, but you will see that there are more interesting applications of print
in the next chapter.
Remember that it is possible to have an empty println command:

System.out.println();

Because there is nothing inside the parentheses to be written to the output line, this
command positions the output cursor at the beginning of the next line. If there are
print commands before this empty println , it finishes out the line made by those
print commands. If there are no previous print commands, it produces a blank
line. An empty print command is meaningless and illegal.

Identifiers and Keywords
The words used to name parts of a Java program are called identifiers.

Identifier
A name given to an entity in a program, such as a class or method.

Identifiers must start with a letter, which can be followed by any number of letters
or digits. The following are all legal identifiers:

first hiThere numStudents TwoBy4