Working with Single Level Inheritance in Java

package ch9.l3;

//Create a superclass.
class A {
	int i, j;
	
	void setij(int i,int j) {
		this.i=i;
		this.j=j;
	}
	
	void showij() {
		System.out.println("i and j: " + i + " " + j);
	}
}

//Create a subclass by extending class A.
class B extends A {
	int k;
	
	void setk(int k) {
		this.k=k;
	}
	
	void showk() {
		System.out.println("k: " + k);
	}
	
	void sum() {
		System.out.println("i+j+k: " + (i+j+k));
	}
}
	
public class SingleInheritance {

	public static void main(String[] args) {
		A objA=new A();
		B objB=new B();
		
		//The superclass may be used by itself.
		objA.setij(10, 20);
		System.out.println("Contents of Super Class A: ");
		objA.showij();
		System.out.println();
		
		/* The subclass can access to all public members of
		 its superclass. */
		objB.setij(5, 6);
		objB.setk(7);
		System.out.println("Contents of Sub Class B: ");
		objB.showij();
		objB.showk();
		System.out.println("Sum of i, j and k in Subclass Object:");
		objB.sum();
	}
}

Contents of Super Class A: 
i and j: 10 20

Contents of Sub Class B: 
i and j: 5 6
k: 7
Sum of i, j and k in Subclass Object:
i+j+k: 18

package ch9.l3;

//Superclass
class Vehicle {
	protected String brand = "Ford"; // Vehicle attribute
	public void honk() { // Vehicle method
		System.out.println("Tuut, tuut!");
	}
}

//Subclass
class Car extends Vehicle {
	private String modelName = "Mustang"; // Car attribute
	public void display() {
		System.out.println("Brand: " + brand + ", Model Name: " + modelName);
	}
}

//Main class
public class VehicleMain {
	public static void main(String[] args) {
		Car myCar = new Car();
		myCar.honk();
		myCar.display();
	}
}

Tuut, tuut!
Brand: Ford, Model Name: Mustang

class Bank {
    protected int balance;

    Bank() {
        balance = 0;
    }

    void showBalance() {
        System.out.println("Current Balance: $" + balance);
    }
}

class SavingsAccount extends Bank {
    void deposit(int amount) {
        balance += amount;
    }
}

public class Main {
    public static void main(String[] args) {
        SavingsAccount myAccount = new SavingsAccount();
        myAccount.deposit(500); // Deposit $500
        myAccount.showBalance(); // Prints "Current Balance: $500"
    }
}