Java Variables

Ankit Mishra July 19, 2019

In this tutorial, you will learn about variables, how to create them, and different data types that Java programming language supports for creating variables.

Java Variables

A variable is a location in memory (storage area) to hold data. The term data type refers to the type of data that can be stored in a variable.
To indicate the storage area, each variable should be given a unique name (identifier). Learn more about Java identifiers.

Primitive Data Types

There are eight primitive data types supported by Java.
Primitive data types are predefined by the language and named by a keyword.

1. byte:

Byte data type is an 8-bit signed two's complement integer.
Minimum value is -128 (-2^7)
Maximum value is 127 (inclusive)(2^7 -1)
Default value is 0
Byte data type is used to save space in large arrays, mainly in place of integers, since a byte is four times smaller than an int.

        
 class ByteExample {
    public static void main(String[] args) {     
     byte range;
     range = 124;
     System.out.println(range);    
     // Error code below. Why?
     // range = 200
    }
}

When you run the program, the output will be:

2. short:

Short data type is a 16-bit signed two's complement integer.
Minimum value is -32,768 (-2^15)
Maximum value is 32,767 (inclusive) (2^15 -1)
Short data type can also be used to save memory as byte data type. A short is 2 times smaller than an int
Default value is 0.

        
class ShortExample {
    public static void main(String[] args) {    
     short temperature;   
     temperature = -200;
     System.out.println(temperature);   
    }
}

When you run the program, the output will be:

        
 -200

3. int:

Int data type is a 32-bit signed two's complement integer.
Minimum value is - 2,147,483,648.(-2^31)
Maximum value is 2,147,483,647(inclusive).(2^31 -1)
Int is generally used as the default data type for integral values unless there is a concern about memory.
The default value is 0.

        
class IntExample {
    public static void main(String[] args) {   
     int range = -4250000;
     System.out.println(range);
    }
}

When you run the program, the output will be:

        
 -4250000

4. long:

Long data type is a 64-bit signed two's complement integer.
Minimum value is -9,223,372,036,854,775,808.(-2^63)
Maximum value is 9,223,372,036,854,775,807 (inclusive). (2^63 -1)
This type is used when a wider range than int is needed.
Default value is 0L.

        
class LongExample {
    public static void main(String[] args) {
     
     long range = -42332200000L;
     System.out.println(range);
    }
}

When you run the program, the output will be:

        
 -42332200000

5. float:

Float data type is a single-precision 32-bit IEEE 754 floating point.
Float is mainly used to save memory in large arrays of floating point numbers.
Default value is 0.0f.
Float data type is never used for precise values such as currency.

        
class FloatExample {
    public static void main(String[] args) {
     
     float number = -42.3f;
     System.out.println(number);
    }
}

When you run the program, the output will be:

        
 -42.3

6. double:

double data type is a double-precision 64-bit IEEE 754 floating point.
This data type is generally used as the default data type for decimal values, generally the default choice.
Double data type should never be used for precise values such as currency.
Default value is 0.0d.

        
class DoubleExample {
    public static void main(String[] args) {
     
     double number = -42.3;
     System.out.println(number);
    }
}

When you run the program, the output will be:

        
 -42.3

7. boolean:

boolean data type represents one bit of information.
There are only two possible values: true and false.
This data type is used for simple flags that track true/false conditions.
Default value is false.

        
class BooleanExample {
    public static void main(String[] args) {
     
     boolean flag = true;
     System.out.println(flag);
    }
}

When you run the program, the output will be:

        
 true

8. char:

char data type is a single 16-bit Unicode character.
Minimum value is '\u0000' (or 0).
Maximum value is '\uffff' (or 65,535 inclusive).
Char data type is used to store any character.

        
class CharExample {
    public static void main(String[] args) {
     
     char letter = '\u0051';
     System.out.println(letter);
    }
}

When you run the program, the output will be:

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