Adapter Design Pattern – Implementation [Mobile Charger]

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Introduction

The Adapter Design Pattern is a structural design pattern used to make two incompatible interfaces work seamlessly together. A classic, intuitive real-world analogy is a Mobile Phone Charger: an electrical wall socket provides high voltage (e.g., 120V or 220V), but a mobile phone only requires 9V to charge. Connecting the phone directly to the wall socket is incompatible, so the mobile charger acts as an adapter converting the incoming voltage to what the phone expects.

Adapter Pattern Mapping

Pattern Role	Component in Example	Description
Client	MobilePhone	Needs 9V power to charge
Target Interface	ITarget	Defines get9Volt() method expected by the client
Adaptee	ElectricSocket	Existing class providing 120V via getVolt()
Adapter	MobilePhoneCharger	Implements ITarget, fetches 120V, and converts it to 9V

Java Code Implementation

1. The Volt Model Class

public class Volt {
    private int volts;

    public Volt(int volts) {
        this.volts = volts;
    }

    public int getVolts() {
        return volts;
    }

    public void setVolts(int volts) {
        this.volts = volts;
    }
}

2. Adaptee: ElectricSocket

public class ElectricSocket {
    public Volt getVolt() {
        return new Volt(120);
    }
}

3. Target Interface: ITarget

public interface ITarget {
    Volt get9Volt();
}

4. Adapter: MobilePhoneCharger

public class MobilePhoneCharger implements ITarget {
    private ElectricSocket electricSocket = new ElectricSocket();

    @Override
    public Volt get9Volt() {
        Volt v120 = electricSocket.getVolt();
        System.out.println("From Electric Socket, charger got: " + v120.getVolts() + "V");
        
        Volt v9 = convert120VoltTo9Volt(v120);
        System.out.println("Mobile phone charger converted 120V to: " + v9.getVolts() + "V");
        return v9;
    }

    private Volt convert120VoltTo9Volt(Volt v) {
        return new Volt(9);
    }
}

5. Client: MobilePhone

public class MobilePhone {
    public void chargeMe() {
        ITarget target = new MobilePhoneCharger();
        Volt volt = target.get9Volt();
        System.out.println("Mobile phone is charging using: " + volt.getVolts() + "V");
    }

    public static void main(String[] args) {
        MobilePhone mobilePhone = new MobilePhone();
        mobilePhone.chargeMe();
    }
}

Console Output

From Electric Socket, charger got: 120V
Mobile phone charger converted 120V to: 9V
Mobile phone is charging using: 9V

Related Tutorials from Ram N Java

• Adapter Design Pattern in Action: Real-World JDBC Driver Example
• Adapter Design Pattern: Introduction and Basics
• Adapter Design Pattern: Class Diagram Overview
• Adapter Design Pattern: Sequence Diagram Explained

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Adapter Design Pattern – Implementation [Mobile Charger]

Adapter Design Pattern – Implementation [Mobile Charger] - Class Diagram

Volt.java

public class Volt
{
private int volts;

public Volt( int v )
{
this.volts = v;
}

public int getVolts()
{
return volts;
}

public void setVolts( int volts )
{
this.volts = volts;
}
}

ElectricSocket.java

public class ElectricSocket

{

public Volt getVolt()

{

return new Volt(120);

}

}

ITarget.java

public interface ITarget
{
public Volt get9Volt();
}

MobilePhoneCharger.java

public class MobilePhoneCharger implements ITarget

{

private ElectricSocket electricSocket = new ElectricSocket();

@Override

public Volt get9Volt()

{

Volt volt = electricSocket.getVolt();

System.out.println("From ElectricSocket MobilePhoneCharger got :" +volt.getVolts() + "v");

Volt convertedVolt=convertVolt(volt,13);

System.out.println("\nMobilePhoneCharger converterd "+volt.getVolts()+"v to "+convertedVolt.getVolts()+"v\n");

return convertedVolt;

}

private Volt convertVolt(Volt v, int i) 
  {

       return new Volt(v.getVolts()/i);

}

}

MobilePhone.java

public class MobilePhone

{

public static void main(String args[])

{

new MobilePhone().chargeMe();

}

public void chargeMe()

{

ITarget target = new MobilePhoneCharger();

Volt volt=target.get9Volt();

System.out.println("Mobile phone is charging using : "+volt.getVolts() + "v");

}

}

Output

From ElectricSocket MobilePhoneCharger got :120v

MobilePhoneCharger converterd 120v to 9v

Mobile phone is charging using : 9v

See also:

Adapter Design pattern - Introduction

Adapter Design Pattern - Real Time Exmaple(Translator)

Adapter Design pattern - Real Time Example (Card Reader)

Adapter Design pattern - Real Time Example (Mobile Charger)

Adapter Design pattern - Real Time Example (Universal Adaptor)

Adapter Design pattern - Real Time Example [JDBC Driver]

Adapter Design pattern - Class diagram

Adapter Design Pattern - Sequence diagram

Adapter Design Pattern - Implementation [Language Translator]

Adapter Pattern - Implementation [Object Adapter]

Adapter Pattern - Implementation [Class Adapter]

Adapter Design Pattern - Key Points

All Design Patterns Links