Variable is a memory location which stores data. In Java, we have to define what type of variable (integer, text, string, etc.), we are storing. After it a fixed memory is assign to each variable. For example, normal integer is assign 4 bytes. We can not assign other type of values to defined variables. For example, if we have defined a variable as integer then we can not assign a text string to that variable. We can modify that variable with different value of same type (say another integer). In java, there are 8 types of primitive variables.
- Integer
- Byte
- Char
- Boolean
- Double
- short
- long
- float
NOTE:
- Run below examples by writing in main method. To print them in console use System.print.out("variable");
- We can give variables any name other than reserved keywords starting with letter, $ or underscore (_).
Integer:
Integer is a 32-bit data type which stores integer values from range - 2,147,483,648 ( -2^31 ) to 2,147,483,647(inclusive) ( 2^31 -1 ).
Example:
- int a = 8;
- a = 10;
Byte:
It is 8-bit data type used to store integer value from -128 to 127 (inclusive).
Example:
- byte a = 23;
- a = -24;
Char:
It is 16-bit unicode character which stores any character.
Example:
- char a = 'a';
- a = 'z';
NOTE: Character is written inside single colons '' but string is written in double colons "".
Boolean:
It is one bit boolean data type which has only two values: true or false.
Example:
- boolean a = true;
- a = false;
Double:
Double data type is a double-precision 64-bit IEEE 754 floating point. This should not be used for precise values such as currency.
Example:
- double a = 56;
- a = 45.98;
Short:
Short data type is a 16-bit signed two's complement integer. Its range is from -32,768 to 32,767 (inclusive).
Long:
Long data type is a 64-bit signed two's complement integer. Its range is -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 (inclusive). It is used when we need wider range for integers.
Example:
- int a = 200000L;
- a = -300000L;
Float:
Float data type is a single-precision 32-bit IEEE 754 floating point. Float data type is also never used for precise values such as currency.
More types:
String:
String is an array of characters. We will read about array in detail later. At this moment you may assume string is a collection of characters. It is simple text.