Instant Update

/*
 * TemperatureModel.java
 */

import java.util.Observable;

/** 
 * In Java, MVC Models can be easily implemented by extending the 
 * java.util.Observable class. The Java Observer/Observable classes provide much 
 * of needed infrastructure for passing registration/notification events back 
 * and forth between Model, View and Controller objects. Here the Observable 
 * superclass contains the methods needed to register observers and notify them 
 * of state changes to the Model.
 * 
 * 

This particular class models temperature. It allows allows clients (e.g., 
 * views and controllers) to query and update the data model both in terms of 
 * Fahrenheit and Celsius temperature scales. Upon construction, the model is 
 * initialized to a temperature of 32F (freezing point of water).
 */
public class TemperatureModel extends Observable {

	public static final int MAX_TEMP_F = 300;		// max allowable temp in the
model
	public static final int MIN_TEMP_F = -200;		// min allowable temp in the
model
	
    private double tempF = 32.0;
    
	/**
	 * Return the current temp, expressed in Fahrenheit. Method may be invoked 
	 * by View objects.
	 * 
	 * @return double temp in F
	 */
    public double getF() { return tempF; }
	
	/**
	 * Return the current temp, expressed in Celsius. Method may be invoked
	 * by View objects
	 * 
	 * @return double temp in C
	 */
    public double getC() { return (tempF-32.0)*5.0/9.0; }
    
	/**
	 * Modify the current temp, argument expressed in Fahrenheit. Method may 
	 * be invoked by Controller objects. Method implements some simple bounds 
	 * checking to make sure the new temp falls in the allowed range (between 
	 * MAX and MIN allowable temps).
	 */
    public void setF(double tempF) {
		// simple bounds checking - thermometer goes up to 300F and down to
-200F
		if ( tempF > MAX_TEMP_F ) tempF = MAX_TEMP_F;
		if ( tempF < MIN_TEMP_F ) tempF = MIN_TEMP_F;
		
        this.tempF = tempF;
        setChanged();       // <-- MVC method that signals state change in the
Observable object 
        notifyObservers();  // <-- MVC method that notifies all interested
observers of the state change
    }

	/**
	 * Modify the current temp, argument expressed in Celsius. Method may 
	 * be invoked by Controller objects. Method implements some simple bounds
	 * checking to make sure the new temp falls in the allowable range (between
	 * MAX and MIN allowable temps).
	 */
    public void setC(double tempC) {
		// simple bounds checking - thermometer goes up to 300F and down to
-200F
		double val = tempC * 9.0 / 5.0 + 32.0;
		if ( val > MAX_TEMP_F ) val = MAX_TEMP_F;
		if ( val < MIN_TEMP_F ) val = MIN_TEMP_F;
		
        this.tempF = val;
        setChanged();       // <-- MVC method that signals state change in the
Observable object 
        notifyObservers();  // <-- MVC method that notifies all interested
observers of the state change
    }
}