Adapter pattern example

Adapter pattern is one of the structural pattern which makes two incompatible interfaces to work together. Idea can be more clear with example. For implementing adapter pattern you can follow given steps.

Here example is of ColorProvider class. This ColorProvider class implements interface called BasicColors which can provide only red, green and blue colours. There is another interface called AdvancedColors whic provides yellow, pink, white and black colors. In this case adapter pattern will make BasicColors and AdvancedColors to work together without any changes in interface of ColorProvider class.

1. Create interface BasicColors as given below.
public interface BasicColors {
void getColor(String color);
}

2. Create interface AdvancedColors as given below.
public interface AdvancedColors {
void getColor();
}

3. Now we can create class ColorProvider which will be used by user.
public class ColorProvider implements BasicColors {
ColorAdapter colorAdapter;
public void getColor(String color) {
if(color.equalsIgnoreCase("red") || color.equalsIgnoreCase("green") || color.equalsIgnoreCase("blue")) {
System.out.print("\nBasic colour " + color + " by BasicColor interface.");
}//if
else {
colorAdapter = new ColorAdapter();
colorAdapter.getColor(color);
}//else
}//getColor
}//class ColorProvider

4. Here we go for ColorAdapter as given below.
public class ColorAdapter implements BasicColors {
AdvancedColors advColor;

public void getColor(String color) {
if(color.equalsIgnoreCase("yellow")) {
advColor = new Yellow();
advColor.getColor();
}//if
else if(color.equalsIgnoreCase("pink")) {
advColor = new Pink();
advColor.getColor();
}//else if
else if(color.equalsIgnoreCase("black")) {
advColor = new Black();
advColor.getColor();
}//else if
else if(color.equalsIgnoreCase("white")) {
advColor = new White();
advColor.getColor();
}//else if
}//getColor
}//class ColorAdapter

5. Now we can implement concreet classes of advanced colors as given below.
public class Yellow implements AdvancedColors {
public void getColor() {
System.out.print("\nAdvanced yellow color.");
}
}

public class Pink implements AdvancedColors {
public void getColor() {
System.out.print("\nAdvanced pink color.");
}
}

public class Black implements AdvancedColors {
public void getColor() {
System.out.print("\nAdvanced black color.");
}
}

public class White implements AdvancedColors {
public void getColor() {
System.out.print("\nAdvanced white color.");
}
}

6. Here we go for demo i.e. for Main class.
public class Main {
public static void main(String args[]) {
ColorProvider cp = new ColorProvider();
cp.getColor("red");
cp.getColor("yellow");
cp.getColor("green");
cp.getColor("pink");
}
}

You can draw UML diagram for better understanding.