super Keyword

public class Animal {
    private String name;
    private int age;
    
    public Animal(String name, int age) {
        this.name = name;
        this.age = age;
    }
    
    public String getName() { return name; }
    public int getAge() { return age; }
}

public class Dog extends Animal {
    private String breed;
    
    public Dog(String name, int age, String breed) {
        super(name, age);      // MUST be first line — calls Animal constructor
        this.breed = breed;    // then initialize Dog-specific fields
    }
    
    public String getBreed() { return breed; }
}

Dog d = new Dog("Rex", 5, "Labrador");
System.out.println(d.getName());  // "Rex" (inherited from Animal)
System.out.println(d.getBreed()); // "Labrador" (Dog-specific)

public class Animal {
    private String name;
    public Animal(String name) {  // only parameterized constructor
        this.name = name;
    }
}

public class Cat extends Animal {
    public Cat() {
        // Java inserts super() here — but Animal has no no-arg constructor!
        // COMPILE ERROR!
    }
}

public class Cat extends Animal {
    public Cat() {
        super("Unknown");  // explicitly call parent's constructor
    }
}

public class Vehicle {
    public Vehicle() {
        System.out.println("Vehicle constructor");
    }
}

public class Car extends Vehicle {
    public Car() {
        super();  // calls Vehicle()
        System.out.println("Car constructor");
    }
}

public class SUV extends Car {
    public SUV() {
        super();  // calls Car()
        System.out.println("SUV constructor");
    }
}

SUV s = new SUV();

Vehicle constructor
Car constructor
SUV constructor

public class Employee {
    private String name;
    private double salary;
    
    public Employee(String name, double salary) {
        this.name = name;
        this.salary = salary;
    }
    
    public String getDetails() {
        return name + " - $" + salary;
    }
}

public class Manager extends Employee {
    private String department;
    
    public Manager(String name, double salary, String dept) {
        super(name, salary);
        this.department = dept;
    }
    
    @Override
    public String getDetails() {
        // Reuse parent's implementation, then add more
        return super.getDetails() + " (" + department + " dept)";
    }
}

Manager m = new Manager("Alice", 85000, "Engineering");
System.out.println(m.getDetails());
// Alice - $85000.0 (Engineering dept)

public class Shape {
    public String describe() {
        return "Shape";
    }
}

public class Rectangle extends Shape {
    private int width, height;
    
    public Rectangle(int w, int h) {
        width = w; height = h;
    }
    
    @Override
    public String describe() {
        return super.describe() + " -> Rectangle(" + width + "x" + height + ")";
    }
}

public class Square extends Rectangle {
    public Square(int side) {
        super(side, side);
    }
    
    @Override
    public String describe() {
        return super.describe() + " -> Square";
    }
}

Square s = new Square(5);
System.out.println(s.describe());
// Shape -> Rectangle(5x5) -> Square

public class Student extends Person {
    private int grade;
    
    public Student(String name, int grade) {
        super(name);           // call Person's constructor
        this.grade = grade;    // refer to this object's field
    }
}

public class C extends B {
    public void method() {
        super.method();        // OK — calls B's version
        // super.super.method(); // COMPILE ERROR — can't skip to A
    }
}

public class GameCharacter {
    private String name;
    private int health;
    
    public GameCharacter(String name, int health) {
        this.name = name;
        this.health = health;
    }
    
    public String getName() { return name; }
    public int getHealth() { return health; }
    
    public String toString() {
        return name + " (HP: " + health + ")";
    }
}

public class Warrior extends GameCharacter {
    private int armor;
    
    public Warrior(String name, int health, int armor) {
        super(name, health);   // initialize name and health via parent
        this.armor = armor;
    }
    
    @Override
    public String toString() {
        return super.toString() + " [Armor: " + armor + "]";
    }
}

public class Paladin extends Warrior {
    private int holyPower;
    
    public Paladin(String name, int health, int armor, int holy) {
        super(name, health, armor);  // calls Warrior constructor
        this.holyPower = holy;
    }
    
    @Override
    public String toString() {
        return super.toString() + " {Holy: " + holyPower + "}";
    }
}

Paladin p = new Paladin("Arthur", 100, 50, 30);
System.out.println(p);
// Arthur (HP: 100) [Armor: 50] {Holy: 30}