variables

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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:

Example

Create a variable called name of type String and assign it the value “John“:

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

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

Example

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

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

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

Example

				
					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:

Example

Change the value of myNum from 15 to 20:

				
					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):

Example

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


				
			

Other Types

A demonstration of how to declare variables of other types:

				
					int myNum = 5;
float myFloatNum = 5.99f;
char myLetter = 'D';
boolean myBool = true;
String myText = "Hello";

				
			

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