Adapter Design Pattern

Mohini Yadav — Sun, 26 Oct 2025 10:06:22 +0000

Adapter design pattern is a structural design pattern.

Definition:

Adapter design pattern converts the interface of a class to another interface that client expects, adapter let's classes work together that couldn't otherwise because of incompatible interfaces
Reference from Head First Design Patterns

There are two variant of Adapter design pattern:

Object Adapter
Class Adapter

Object adapter pattern uses composition, class adapter pattern uses inheritance. (It's not possible to implement class adapter pattern in java as multiple inheritance is not supported)

UML diagram of an adapter design pattern:

Use Cases:

Adapter pattern is used as a bridge/wrapper to work with legacy code.

public interface Target {
public void request();
}

public interface Adaptee {
public void processRequest();
}


public class Adapter implements Target {
private Adaptee adaptee;

public Adapter(Adaptee adaptee) {
this.adaptee = adaptee;
}

public void request() {
adaptee.processRequest();
}
}

CAP Theorem

Mohini Yadav — Fri, 02 May 2025 01:33:12 +0000

CAP - Consistency, Availability and Partition tolerance

According to CAP theorem, we can achieve any two out of three guarantees in a distributed system.

Consistency - Application will return the most recent write to client.

Availability - Application will return reasonable response in reasonable amount of time.

Partition Tolerance - Application will continue to work even in the case of network partitions

Network Partition - It is a scenario in distributed system, when one node is not able to communicate with other node because of network disruption/failure, it divides the network into groups.

There are two options CP and AP.

CP - Consistency/Partition Tolerance
Wait for the response from a partitioned node which could also result into an error response.

AP - Availability/Partition Tolerance
Application will continue to function with the data it have, it could be a stale.

DEV Community: Mohini Yadav

Adapter Design Pattern

Definition:

UML diagram of an adapter design pattern:

Use Cases:

CAP Theorem