Hint:
here is the code of class Spices .
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);
}
}
Here is the code from Listing 12.5 on Page 821.
public class StringLinkedListSelfContained
{
private ListNode head;
public StringLinkedListSelf( )
{
head = null;
}
/**
Displays the data on the list.
*/
public void showList( )
{
ListNode position = head;
while (position != null)
{
System.out.println(position.data);
position = position.link;
}
}
/**
Returns the number of nodes on the list.
*/
public int length( )
{
int count = 0;
ListNode position = head;
while (position != null)
{
count++;
position = position.link;
}
return count;
}
/**
Adds a node containing the data addData at the
start of the list.
*/
public void addANodeToStart(String addData)
{
head = new ListNode(addData, head);
}
/**
Deletes the first node on the list.
*/
public void deleteHeadNode( )
{
if (head != null)
head = head.link;
else
{
System.out.println("Deleting from an empty list.");
System.exit(0);
}
}
/**
Sees whether target is on the list.
*/
public boolean onList(String target)
{
return find(target) != null;
}
// Returns a reference to the first node containing the
// target data. If target is not on the list, returns null.
private ListNode find(String target)
{
boolean found = false;
ListNode position = head;
while ((position != null) && !found)
{
String dataAtPosition = position.data;
if (dataAtPosition.equals(target))
found = true;
else
position = position.link;
}
return position;
}
public String[] toArray( )
{
String[] anArray = new String[length( )];
ListNode position = head;
int i = 0;
while (position != null)
{
anArray[i] = position.data;
i++;
position = position.link;
}
return anArray;
}
private class ListNode
{
private String data;
private ListNode link;
public ListNode( )
{
link = null;
data = null;
}
public ListNode(String newData, ListNode linkValue)
{
data = newData;
link = linkValue;
}
}
}
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