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Variables in a program, as you may have noticed, serve as placeholders for data handled by the program. Variables’
values can change while the program is running.
Local variables are what you’ve seen so far in this section. These variables are only accessible within the methods in
which they are stated.
3.2.2 Primitive Data Types
We may use six more data types in addition to the two Java data types (int, double) that you saw in the Percentage
Calculator program. There are eight primitive data types in Java which are given in the table below:
Data Type Type of values Size
Byte Integer 8-bit
Short Integer 16-bit
Int Integer 32-bit
Long Integer 64-bit
Float Floating Point 32-bit
Double Floating Point 64-bit
Char Character 16-bit
Boolean True or False 1-bit
Rules for naming Variable Name
Some rules for naming variables are as follows:
Ð ÐVariable names can begin with either an alphabetic character, an underscore (_), or a dollar sign ($). However,
convention is to begin a variable name with a letter. They can consist of only alphabets, digits, and underscore.
Ð ÐVariable names must be one word. Spaces are not allowed in variable names. Underscores are allowed.
“total_marks” is fine but “total marks” is not.
Ð ÐThere are some reserved words in Java that cannot be used as variable names, for example – int.
Ð ÐJava is a case-sensitive language. Variable names written in capital letters differ from variable names with the same
spelling but written in small letters. For example, the variable name “percentage” differs from the variable name
“PERCENTAGE” or “Percentage”.
Ð ÐIt is good practice to make variable names meaningful. The name should indicate the use of that variable.
Ð ÐYou can define multiple variables of the same type in one statement by separating each with a comma. For example,
you can define three integer variables as shown: int num1, num2, num3;
3.2.3 String Variables
We use variables to hold numeric data in the previous section’s Percentage Calculator program. Variables are frequently
used to hold textual data, such as a student’s name.
A single character can be stored in a variable of the primitive data type char. To provide a char variable a value, we
enclose the character in single quotes.
char middle_name = ‘m’;
To store more than one character, we use the String class in Java. To assign a text value to a String variable we enclose
the text between double quotes.
For example,
String first_name = “Mayank”; String last_name = “Saxena”;
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