Another set of eyes

Question

I could use a second look. Why is name outputting null rather than "no name yet?"
import java.util.Scanner;
public class Exercise5
    public static void main(String[] args)
       //Create the contructors
        Species species1 = new Species();
        Species species2 = new Species();
        Species species3 = new Species();
        //Output the initial values of the three constructors
        System.out.println("==================== Initial Values ====================");
        System.out.println("\nSpecies 1");
        species1.writeOutput( );
        System.out.println("\nSpecies 2");
        species2.writeOutput( );
        System.out.println("\nSpecies 3");
        species3.writeOutput( );
import java.util.Scanner;
Class for data on endangered species.
public class Species
    private String name;
    private int population;
    private double growthRate;
    public void readInput( )
        Scanner keyboard = new Scanner(System.in);
        System.out.println("What is the species' name?");
        name = keyboard.nextLine( );
        System.out.println(
                      "What is the population of the species?");
        population = keyboard.nextInt( );
        while (population < 0)
            System.out.println("Population cannot be negative.");
            System.out.println("Reenter population:");
            population = keyboard.nextInt( );
        System.out.println("Enter growth rate (% increase per year):");
       growthRate = keyboard.nextDouble( );
    public void writeOutput( )
         System.out.println("Name: = " + name);
         System.out.println("Population: = " + population);
         System.out.println("Growth rate: = " + growthRate + "%");
     Precondition: years is a nonnegative number.
     Returns the projected population of the calling object
     after the specified number of years.
    public int predictPopulation(int years)
          int result = 0;
        double populationAmount = population;
        int count = years;
        while ((count > 0) && (populationAmount > 0))
            populationAmount = (populationAmount +
                          (growthRate / 100) * populationAmount);
            count--;
        if (populationAmount > 0)
            result = (int)populationAmount;
        return result;
    public void setSpecies(String newName, int newPopulation,
                           double newGrowthRate)
        name = newName;
        if (newPopulation >= 0)
            population = newPopulation;
        else
            System.out.println("ERROR: using a negative population.");
            System.exit(0);
        growthRate = newGrowthRate;
    public String getName( )
        return name;
    public int getPopulation( )
        return population;
    public double getGrowthRate( )
        return growthRate;
    public boolean equals(Species otherObject)
        return (name.equalsIgnoreCase(otherObject.name)) &&
               (population == otherObject.population) &&
               (growthRate == otherObject.growthRate);
    //set the default species constructor
    public void Species ()
          String name = "No name yet";
          int population = 0;
          double growthRate = 0.0;
     //set a constructor using just the initialName
     public void Species(String initialName)
          String name = initialName;
          int population = 0;
          double growthRate = 0.0;
     //set a constructor using initialName and initialPopulation
     public void Species(String initialName, int initialPopulation, double initialGrowthRate)
          String name = initialName;
          int population = initialPopulation;
          double growthRate = initialGrowthRate;
}

Answer 1

warnerja wrote:
public void Species ()And don't forget the other hint: The above is NOT defining a constructor. It is defining a method named "Species", which you never invoke, so even if you just change the code as suggested so far, you'll still have a null.<GRUMBLE>
... and in my humble opinion both these "common problems" should result in compiler warning.
public void Species ()
                    ^
STYLE_WARNING: The 'public void Species()' method has the same name as the containing class, making it look like a
constructor. This method name is confusing to other programmers, and is a likely cause of future bugs. This is
most commonly a mistake. If you meant 'Species()' to be a constructor then remove the return type. If you
meant this to be a method then you should rename it.
    String name = "No name yet";
    ^
STYLE_WARNING: The local variable 'name' hides the class attribute of the same name (this.name). This is confusing,
especially to other programmers, and is a common cause of bugs. Consider renaming the local variable, or
the attribute.</GRUMBLE>