People & Cars example algorithm

With static

Here’s a simple classic Java example using ArrayList:

import java.util.ArrayList;

public class Main {

    // Simple Person class
    static class Person {
        String name;
        int age;

        Person(String name, int age) {
            this.name = name;
            this.age = age;
        }

        @Override
        public String toString() {
            return "Person{name='" + name + "', age=" + age + "}";
        }
    }

    public static void main(String[] args) {
        // Create the ArrayList
        ArrayList<Person> people = new ArrayList<>();

        // Add 10 Person objects
        for (int i = 1; i <= 10; i++) {
            people.add(new Person("Person" + i, 20 + i));
        }

        // Print the list
        System.out.println(people);
    }
}

Output example:

[Person{name='Person1', age=21}, Person{name='Person2', age=22}, ... , Person{name='Person10', age=30}]

You can change the name and age values inside the loop as needed.

In the example, Person is declared as a static nested class inside Main.

Why static?

static class Person {
    ...
}

  • A non-static inner class is tied to an instance of the outer class (Main).
    You would need an object of Main just to create a Person.

  • A static nested class does not need an instance of the outer class.
    You can create it directly with new Person(...), which is what we have at simple example.

Alternative (more common in real projects)

Most people prefer putting the Person class in its own file:

// Person.java
public class Person {
    String name;
    int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public String toString() {
        return "Person{name='" + name + "', age=" + age + "}";
    }
}
// Main.java
import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        ArrayList<Person> people = new ArrayList<>();

        for (int i = 1; i <= 10; i++) {
            people.add(new Person("Person" + i, 20 + i));
        }

        System.out.println(people);
    }
}

This way we don’t need static at all.

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