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Java Program to get Rate of interest of banks using interface Bank.

Java Code Example — Abstract and Interface Programs

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Java Program to get Rate of interest of banks using interface Bank.

Objective

Write a Java program to fetch different Bank Interest Rates using a common Interface.

Algorithm / Approach

  1. Create an interface Bank with a method public float roi();.
  2. Create classes for HDFC, PNB, and SBI that all implement the Bank interface.
  3. Each bank class should return its specific Rate of Interest (ROI) from the overridden roi() method.
  4. In main, use the Bank interface reference to sequentially instantiate the different banks and print their ROIs.
HDFC.java 
interface Bank
{
 public float roi();
}
class HDFC implements Bank {
 public float roi() {
  return 4.5f;
 }
}
class PNB implements Bank {
 public float roi() {
  return 4.9f;
 }
}
class SBI implements Bank {
 public float roi() {
  return 3.5f;
 }
}
class Main {
 public static void main(String[] a)
 {
  Bank b = new HDFC();
  System.out.println("HDFC- "+b.roi());
  Bank b2 = new PNB();
  System.out.println("PNB- "+b2.roi());
  Bank b3 = new SBI();
  System.out.println("SBI- "+b3.roi());
 }
}

Expected Output

HDFC- 4.5
PNB- 4.9                         
SBI- 3.5

Explanation of the Program

  • This program is a classic example of polymorphism enabled by interfaces.
  • The main program only needs to know about the Bank interface. It doesn't care *how* a specific bank calculates its ROI, only that it is guaranteed to have a method called roi().
  • This loose coupling makes the code highly scalable. Adding a new bank (like ICICI) requires zero changes to the main logic; you simply create a new class that implements the interface.

Complexity

Time Complexity O(1)
Space Complexity O(1)
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