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:

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.

To create a variable that should store text, look at the following example:

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

To create a variable that should store a number, look at the following example:

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

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

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

Note that 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);

Display Variables

The println() method is often used to display variables.

To combine both text and a variable, use the + character:

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

You can also use the + character to add a variable to another variable:

String firstName = "John ";
String lastName = "Doe";
String fullName = firstName + lastName;
System.out.println(fullName);

For numeric values, the + character works as a mathematical operator (notice that we use int (integer) variables here):

int x = 5;
int y = 6;
System.out.println(x + y); // Print the value of x + y

From the example above, you can expect:

• x stores the value 5
• y stores the value 6
• Then we use the println() method to display the value of x + y, which is 11

Declare Many Variables

To declare more than one variable of the same type, you can use a comma-separated list:

int x = 5;
int y = 6;
int z = 50;
System.out.println(x + y + z);

You can simply write:

int x = 5, y = 6, z = 50;
System.out.println(x + y + z);

One Value to Multiple Variables

You can also assign the same value to multiple variables in one line:

int x, y, z;
x = y = z = 50;
System.out.println(x + y + z);