Java Variables

Variables are containers for storing data values.

In Java there are different types of variables, for example:

Declaring Variables

To create a variable, the type should be specified and value is assigned to it.

Syntax:

type variable = value

Where type is a Java variable types ( such as int, String, float, char, Boolean), variable is the name of the variable (such as x ), the = is the assignment operator which is used to assign values to the variables and value is the value assigned to the variable (such as x=10)

Examples:

String name = "SparkDatabox";
int value = 1000;
float z = 3.4F;

We can declare a variable without assigning the value to it. The value can be assigned to the variable later as well. For example,

int value;
value = 1000;

The above one gives the same meaning as the previous one.

Display Variables

The println() method  is used to display variables. To concatenate the variables with the strings, we use ‘+’ operator.

Example:

String name = "Databox";
System.out.println("Spark"+name);

For numeric values, the ‘+’ operator works as a mathematical operator to add the numbers.

Example:

int x = 2;
int y = 3;
System.out.println(x+y);

Declaring many variables

We can declare more than one variable of the same type with a comma-separated.

Example:

int x = 2, y = 3, z = 4;
System.out.println(x+y+z);

Java Identifiers

All Java variables should be identified with unique names. These unique names are known as identifiers. There are some set of rules for constructing names for variables such as,

• The identifier names can contain letters, digits, underscores and dollar signs.
• The identifier names should begin with a letter.
• The identifiers can also begin with underscore (_) and dollar sign ($). But generally this is rarely used.
• The identifiers names are case sensitive (“myvar” and “myVar” are different variables).
• The identifier names should always start with lowercase and it cannot contain whitespaces.
• It should not contain Reserved  words like “String” or “int”.