Basic literals: numbers, strings and characters

Regardless of its complexity, a program always performs operations on numbers, strings, and other values. These values are called literals. There are many different sorts of literals in Java, but in this topic we will focus only on a few of them: the ones that surround us all the time in everyday life.

Basic literals in Java

Consider literals as groceries. To use them, usually you need to store them somewhere. Typically, they are stored in variables, which you can think of as containers designed to hold a specific type of data.

Variables can only store matching data. You wouldn't want to accidentally put honey in a cardboard cereal box or pour cereal into a salt shaker. To prevent such mistakes, learn to distinguish between the basic literals: integer numbers, strings, and characters.

Integer numbers

You use these numbers to count things in the real world as natural numbers. Integer numbers also include zero and negative ones. Here are several examples of valid integer number literals separated by commas: 0, 1, 2, 10, 11, -100.

Here is how integers can be used in code:

int numApples = 1000;

Reading code is crucial for anyone in IT, so let's parse it together. Here you put the integer 1000 into a variable of an integer type, called numApples. This is similar to filling a container with its designated contents!

You can increase code readability by dividing the digit into blocks with underscores: 1_000_000 is more readable than 1000000. So let's pack our apples to make selling them easier:

int numPackedApples = 1_000_000;

Fear not if these code snippets aren't 100% clear to you yet! They aim to help you develop the skill of code reading. Just grasp the overall meaning and follow your study plan, and you'll be writing your own code in no time!

Characters

A character is a single symbol, denoted with single quotes. You can use character literals to represent single letters like 'A', 'x', digits from '0' to '9', whitespaces (' '), and other characters or symbols like '$'.

Be mindful of quotes and avoid confusing characters representing digits with the digits themselves:

char charOne = '1'
int numOne = 1

Fun fact: characters sit between integers and strings: they resemble strings, yet you can do math with them.

Strings

A string is a sequence of characters, encapsulated by double quotes. It represents text-based information, such as an advertising line, a webpage address, or a website login name. Here are some valid examples: "text", "I want to know Java", "123456", "[email protected]". As you can see, a string can include letters, digits, whitespaces, and other characters altogether.

A string consisting of a single character like "A" is also a valid string, but do not confuse it with the 'A' character. Note the difference in quotes!

char singleQuoted = 'A'
String doubleQuoted = "A"

Printing literals using variables

In Java, assigning literals to variables and printing them using System.out.println is a fundamental operation. To assign a literal to a variable, you first declare the variable with its type and then initialize it with a literal value. For instance, you might declare an integer variable like int number = 42;, where 42 is the literal value assigned to number. Similarly, for a string variable, you could write String greeting = "Hello";, where "Hello" is the string literal assigned to greeting. Once the variables are initialized, you can use System.out.println to print their values to the consolе:

public class Main {
    public static void main(String[] args) {
        int number = 42;
        String greeting = "Hello";
        
        System.out.println(number);
        System.out.println(greeting);
    }
}

For example, System.out.println(number); will output the value 42, and System.out.println(greeting); will display Hello. This approach allows you to store and manipulate literal values in variables and then output them as needed for various purposes in your Java programs.

Conclusion

You have learned to distinguish between the following literals:

• 123 is an integer number, "123" is a string;

• 'A' is a character, "A" is a string;

• '1' is a character, 1 is an integer number.