AVAJAVA Web Tutorials

(Continued from page 1)

TemperatureClassReporter is a class adapter. It extends CelciusReporter (the adaptee) and implements TemperatureInfo (the target interface). If a temperature is in Celcius, TemperatureClassReporter utilizes the temperatureInC value from CelciusReporter. Fahrenheit requests are internally handled in Celcius.

TemperatureClassReporter.java

package com.cakes;

// example of a class adapter
public class TemperatureClassReporter extends CelciusReporter implements TemperatureInfo {

	@Override
	public double getTemperatureInC() {
		return temperatureInC;
	}

	@Override
	public double getTemperatureInF() {
		return cToF(temperatureInC);
	}

	@Override
	public void setTemperatureInC(double temperatureInC) {
		this.temperatureInC = temperatureInC;
	}

	@Override
	public void setTemperatureInF(double temperatureInF) {
		this.temperatureInC = fToC(temperatureInF);
	}

	private double fToC(double f) {
		return ((f - 32) * 5 / 9);
	}

	private double cToF(double c) {
		return ((c * 9 / 5) + 32);
	}

}

TemperatureObjectReporter is an object adapter. It is similar in functionality to TemperatureClassReporter, except that it utilizes composition for the CelciusReporter rather than inheritance.

TemperatureObjectReporter.java

package com.cakes;

// example of an object adapter
public class TemperatureObjectReporter implements TemperatureInfo {

	CelciusReporter celciusReporter;

	public TemperatureObjectReporter() {
		celciusReporter = new CelciusReporter();
	}

	@Override
	public double getTemperatureInC() {
		return celciusReporter.getTemperature();
	}

	@Override
	public double getTemperatureInF() {
		return cToF(celciusReporter.getTemperature());
	}

	@Override
	public void setTemperatureInC(double temperatureInC) {
		celciusReporter.setTemperature(temperatureInC);
	}

	@Override
	public void setTemperatureInF(double temperatureInF) {
		celciusReporter.setTemperature(fToC(temperatureInF));
	}

	private double fToC(double f) {
		return ((f - 32) * 5 / 9);
	}

	private double cToF(double c) {
		return ((c * 9 / 5) + 32);
	}

}

The AdapterDemo class is a client class that demonstrates the adapter pattern. First, it creates a TemperatureClassReporter object and references it via a TemperatureInfo reference. It demonstrates calls to the class adapter via the TemperatureInfo interface. After this, it creates a TemperatureObjectReporter object and references it via the same TemperatureInfo reference. It then demonstrates calls to the object adapter.

AdapterDemo.java

package com.cakes;

public class AdapterDemo {

	public static void main(String[] args) {

		// class adapter
		System.out.println("class adapter test");
		TemperatureInfo tempInfo = new TemperatureClassReporter();
		testTempInfo(tempInfo);

		// object adapter
		System.out.println("\nobject adapter test");
		tempInfo = new TemperatureObjectReporter();
		testTempInfo(tempInfo);

	}

	public static void testTempInfo(TemperatureInfo tempInfo) {
		tempInfo.setTemperatureInC(0);
		System.out.println("temp in C:" + tempInfo.getTemperatureInC());
		System.out.println("temp in F:" + tempInfo.getTemperatureInF());

		tempInfo.setTemperatureInF(85);
		System.out.println("temp in C:" + tempInfo.getTemperatureInC());
		System.out.println("temp in F:" + tempInfo.getTemperatureInF());
	}

}

The console output of the execution of AdapterDemo is shown here.

Console Output

class adapter test
temp in C:0.0
temp in F:32.0
temp in C:29.444444444444443
temp in F:85.0

object adapter test
temp in C:0.0
temp in F:32.0
temp in C:29.444444444444443
temp in F:85.0