Is the following declaration correct?

int answer;
double rate = 0.05;

Answer:

Yes — as long as the names answer and rate have not already been used.

Names for Variables

The programmer picks a name for each variable in a program. Various things in a program are given names. A name chosen by a programmer is called an identifier. Here are the rules for identifiers:

Use only the characters 'a' through 'z', 'A' through 'Z', '0' through '9', character '_', and character '$'.
An identifier can not contain the space character.
Do not start with a digit.
An identifier can be any length.
Upper and lower case count as different characters.
- SUM and Sum are different identifiers.
An identifier can not be a reserved word.
An identifier must not already be in use in this part of the program.

A reserved word is a word which has a predefined meaning in Java. For example int, double, true, and import are reserved words. Rather than worry about the complete list of reserved words, just remember to avoid using names that you know already mean something, and be prepared to make a change if you accidentally use a reserved word you didn't know.

As a matter of programming style, a name for a variable usually starts with a lower case letter. If a name for a variable is made of several words, capitalize each word except the first. For example, payAmount and grandTotal. These conventions are not required by syntax, but make programs easier to read.

QUESTION 6:

Which of the following variable declarations are correct? (click on a declaration to verify your answer)

int myPay, yourPay; 

long good-by ; 

short shrift = 0; 

double bubble = 0, toil= 9, trouble = 8 

byte the bullet ; 

int  double; 

char thisMustBeTooLong ; 

int 8ball; 

float a=12.3; b=67.5; c= -45.44;