Variables and types

Java is statically typed: every variable is declared with a type that never changes. int age = 36; holds a whole number, double height = 1.7; a number with a decimal point, boolean open = true; a yes or no, char grade = 'A'; one character in single quotes, and String name = "Ada"; text. Assigning again replaces the value, but only with a value of the same type; age = "old"; does not compile.

Variables declared inside main live only inside it. A variable declared at class level with static belongs to the class and can be read from anywhere as Main.name; the checks in the first lessons read your values that way. Names are camelCase: totalPrice.

A Java file can hold more than one class. This course ends in a project, a small library system, and a few lessons along the way build one of its classes; the first is Policy, two constants marked static final, which means they can never change.

public class Main {
    static String city = "Lisbon";

    public static void main(String[] args) {
        int population = 545000;
        city = "Porto";
        System.out.println(city + " " + population);
    }
}

Your task

Declare three static variables on Main: name (a String with any text), age (an int), and height (a double). In main, print <name> is <age>, for example Ada is 36, by joining the variables with +.

Then add the class Policy after Main with two constants: static final int LOAN_DAYS = 14; and static final int DAILY_FEE_CENTS = 25;.

Part of the final project. Policy holds the loan length and the daily late fee the library charges. It is saved in this browser and loaded into Project: the library when you get there.

public class Main {
    static String name = "Ada";
    static int age = 36;
    static double height = 1.7;

    public static void main(String[] args) {
        System.out.println(name + " is " + age);
    }
}

class Policy {
    static final int LOAN_DAYS = 14;
    static final int DAILY_FEE_CENTS = 25;
}