algaecolony.java

卡耐基梅隆大学 SSD课程体系 ssd1 exesice8 答案

/*!Begin Snippet:AlgaeColony*/
/*
 * Created on Jul 4, 2003
 *
 */

/**
 * AlgaeColony does not move. If there is sunlight, a portion of the solar 
 * energy will be converted into life-energy.
 * 
 * @author iCarnegie av
 */
public class AlgaeColony extends LivingBeing {

	/**
	 * Lowest possible energy needed for a baby to survive. 
	 */
	private static final int BABY_MIN_ENERGY = 5;

	/**
	 * Maximum energy that a baby can store. 
	 */
	private static final int BABY_MAX_ENERGY = 255;
	
	/**
	 * Amount of energy needed to live for a block of time.
	 */
	private static final int ENERGY_TO_LIVE = 1;
	
	/**
	 * Name of species
	 */	
	private static final String SPECIES = "Algae";

	/**
	 * Number of Algae objects created so far.
	 */
	private static int nAlgaeCreated = 0;

	
	/**
	 * Constructor. Initialize an algae to start life at a specified 
	 * location with a specified energy. If location is out of bounds,
	 * locate the algae at the nearest edge.
	 * 
	 * @param initialRow - the row at which the algae is located
	 * @param initialColumn - the column at which the algae is located
	 * @param initialSimulation - the simulation that the algae belongs to
	 */
	public AlgaeColony(
		int initialRow,
		int initialColumn,
		Simulation initialSimulation) {
			
		super(
			initialRow,
			initialColumn,
			initialSimulation,
			SPECIES + nAlgaeCreated,
			BABY_MIN_ENERGY,
			BABY_MAX_ENERGY);
			
			++nAlgaeCreated;
	}

	/**
	 * The mechanism to display Algae is to use its color.
	 * 
	 * @return a constant defined in {@link Simulation#COLOR Simulation} class
	 */
	public String getDisplayMechanism() {
		return Simulation.COLOR;
	}
	
	/**
	 * Get the species that the algae belongs to
	 * 
	 * @return a string indicating the species.
	 */
	public String getSpecies() {
		return SPECIES;
	}

	/**
	 * Get the color of Algae
	 * 
	 * @return - the color as a string in hexademinal notation
	 */
	public String getColor() {

		// Concept example: Distinction between local variable 
		// and instance variable.
		// Note: Since energyLevel is declared as a *private* instance 
		// in LivingBeing it is not visible here. 
		// We create a local variable 
		// whose name happens to be the same as the instance variable.
		// The local variable is assigned a value that is the 
		// instance variable's value.
		int energy = getEnergy();
		
		// Let us limit the energy to the color range of 0 to 255.
		if (energy < 0) {
			energy = 0;
		}
		
		if (energy > 255) {
			energy = 255;
		}
		// Convert energy scale into green scale expressed in hex form.
		String greenLevel = Integer.toHexString(energy);

		// If energy is a value less than 16, 
		// there will be only one character.
		// Since we need 2 characters for green, we pad left with a "0".
		if (energy < 16) {
			greenLevel = "0" + greenLevel;
		}

		// Now prepend with "00" to indicate there is no red 
		// and append with "00" to indicate there is no blue.
		return "#00" + greenLevel + "00";
	}

	/**
	 * Algae is being eaten up. 
	 * So, relinquish energy up to the amount requested.
	 * If no energy remains, die.
	 * 
	 * @param energyWanted - amount of energy requested - expressed as int.
	 * @return - the amount of energy that algae can give up. 
	 * If the requested energy is greater than the available energy,
	 * only the available energy will be given up. 
	 */
	public int giveUpEnergy(int energyWanted) {

		int energy = getEnergy();

		// We do not know what it means to want negative energy!!!
		if (energyWanted < 0) {
			return 0;
		}

		if (energyWanted < energy) {
			setEnergy(energy - energyWanted);
		} else // caller is asking for more than energy than available. 
			// Give only what I have. 
			// I will die since my energy level falls below minimum.
			{
			energyWanted = energy;
			setEnergy(getMinEnergy() - 1);
		}
		return energyWanted;
	}

	/**
	 * Algae lives its life. May gain or lose energy.
	 */
	public void liveALittle() {

		if (isDead()) {
			return;
		}

		super.liveALittle();
		int row = getRow();
		int column = getColumn();
		int sun = simulation.getSunlight(row, column);

		// Let us assume that algae can convert 50% of 
		// solar energy into life-energy.
		// Algae has to give up some energy to live.
		setEnergy((int) (sun * 0.5) + getEnergy() - ENERGY_TO_LIVE);
	}
}
/*!End Snippet:AlgaeColony*/