Java Variables

Variables are containers for storing data values.

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

• String - stores text, such as "Hello". String values are surrounded by double quotes.
• int - stores integers (whole numbers), without decimals, such as 123 or -123.
• float - stores floating point numbers, with decimals, such as 19.99 or -19.99.
• char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes.
• boolean - stores values with two states: true or false.

Declaring (Creating) Variables

To create a variable, you must specify the type and assign it a value:

// Syntax
type variableName = value;

Where type is one of Java's types (such as int or String), and variableName is the name of the variable (such as x or name). The equal sign = is used to assign values to the variable.

Example 1: Creating a String Variable

Create a variable called name of type String and assign it the value "John". Then, we use println() to print the name variable:

String name = "John";
System.out.println(name);

Example 2: Creating an Integer Variable

Create a variable called myNum of type int and assign it the value 15:

int myNum = 15;
System.out.println(myNum);

Example 3: Declaring a Variable Without Assigning a Value

You can also declare a variable without assigning a value initially and assign the value later:

int myNum;
myNum = 15;
System.out.println(myNum);

Example 4: Overwriting a Variable's Value

If you assign a new value to an existing variable, it will overwrite the previous value:

int myNum = 15;
myNum = 20;  // myNum is now 20
System.out.println(myNum);

Final Variables

If you don't want others (or yourself) to overwrite existing values, use the final keyword (this will declare the variable as "final" or "constant", which means unchangeable and read-only):

final int myNum = 15;
myNum = 20;  // This will generate an error: cannot assign a value to a final variable