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Java

Variables & Data Types

Unlike Python or JavaScript, Java variables need an explicit type when declared: int age = 21;.

Example: declaring several typed variables

public class Main {
    public static void main(String[] args) {
        String name = "Ada";
        int age = 21;
        System.out.println(name + " is " + age + " years old.");
    }
}
Ada is 21 years old.

Common types: int (whole numbers), double (decimals), boolean (true/false), and String (text — capitalised, since it's technically a class, not a primitive type like the others). Try assigning a number to name instead of text, and Java refuses to even compile the program — this compile-time type checking is exactly what "statically-typed" means in practice, not just a definition to memorize.

Example
public class Main {
    public static void main(String[] args) {
        String name = "Ada";
        int age = 21;
        System.out.println(name + " is " + age + " years old.");
    }
}
Output
Ada is 21 years old.
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