static Members and toString

static: shared by the whole class

A normal field belongs to each object. A static field belongs to the class itself, so there is only one, shared by all objects:

class Player {
    static int count = 0;
    String name;

    Player(String name) {
        this.name = name;
        count++;
    }
}

public class Main {
    public static void main(String[] args) {
        new Player("Asha");
        new Player("Ravi");
        new Player("Meera");
        System.out.println("Players created: " + Player.count);
    }
}

Output

Players created: 3

Think of it like this: Each student has their own name (normal field), but the whole class shares one classroom clock (static field).

A static method also belongs to the class, so you call it without making an object – like Math.sqrt(). That's why main is static: Java can start it before any object exists.

Printing an object

Printing an object gives an odd code like Point@1b6d3586. Give your class a toString() method and Java uses it whenever the object is printed or joined to text:

class Point {
    int x, y;

    Point(int x, int y) {
        this.x = x;
        this.y = y;
    }

    @Override
    public String toString() {
        return "(" + x + ", " + y + ")";
    }
}

public class Main {
    public static void main(String[] args) {
        Point p = new Point(3, 7);
        System.out.println(p);
        System.out.println("The point is " + p);
    }
}

Output

(3, 7)
The point is (3, 7)

@Override tells Java “I'm replacing a method that already exists”. You'll learn why in the next module.

null: no object

A variable of a class type can hold null, meaning “no object here”. Using it crashes:

public class Main {
    public static void main(String[] args) {
        String name = null;
        System.out.println(name.length());
    }
}

Output (Java stops with an error)

Exception in thread "main" java.lang.NullPointerException

Common mistake: NullPointerException is the most common Java crash. Make sure an object was created with new (or isn't null) before you use it.