Population program

[neonman14]

Hello I am in Intro to Java Programming and I am having problems with assignment. The Homework assignment is called Population.

Population

Write a program that will predict the size of a population of organisms. The program should ask for the starting number of organisms, their average daily population increase (as a percentage), and the number of days they will multiply. For example, a population might begin with two organisms, have an average daily increase of 50%, and will be allowed to multiply for 7 days. The program should use a loop to display the size of the population each day.

Input Validation: Do not accept a number less than two for the starting size of the population. Do not accept a negative number for average daily population increase. Do not accept a number less than one for the number of days they will multiply.

Here is what I have done so far!

import java.util.scann er; // Needed for the scanner class




/**
This program demonstrates a user controlled loop
*/

public class Population

public static void main(String[] args)
{
int Size,
Days,
increase,
number,
Temp;
String input; // To Hold the user's input

//Create a Scanner object for keyboard input.
Scanner Keyboard = new scanner(System. in);


int startingSize = 0, dailyIncrease = 0, numberOfDays = 0;
int temp = 0;


//accept initial user input here

while (startingSize < 2)
{
System.out.prin t("Please enter a number that is greater than 1 for the population size: ");
startingSize = keyboardInput.n extInt(System.i n);
}

while (dailyIncrease < 0)
{
System.out.prin t("Enter a positive integer for the population size increase: ");
dailyIncrease = keyboardInput.n extInt(System.i n);
}

//do the same while loop for numberOfDays as a positive number > 0


temp = startingSize;
dailyIncrease = dailyIncrease + 1;

for(int i = 0; i < numberOfDays; i++)
{
System.out.prin tln("Day " + i);
System.out.prin tln("Number " + temp);
temp = temp * dailyIncrease;
}

[neonman14]

Thank you! I went and change that and yeah that is just me not paying attention! I went in and changed that and I went and compile it again ofter the chang and I got thes errors:

C:\Documents and Settings\Admini strator\My Documents\Popul ation.java:25: cannot find symbol
symbol : method nextInt(java.io .InputStream)
location: class java.util.Scann er
startingSize = keyboard.nextIn t(System.in);
^
C:\Documents and Settings\Admini strator\My Documents\Popul ation.java:31: cannot find symbol
symbol : method nextInt(java.io .InputStream)
location: class java.util.Scann er
dailyIncrease = keyboard.nextIn t(System.in);
^
2 errors

Tool completed with exit code 1

[Ganon11]

I don;'t think you need to pass System.in to each function of the Scanner - since you used System.in in the constructor, I think you can just use

startingSize = keyboard.nextInt();

[neonman14]

Thanks You! I cahnged that and it compiled good! But I don't think it doing what I need it to do!

When I compile it it just asks for a number greater then 1 in Population and after you type 2 or what every number it finished!

here is my compelte assignment with out any errors!

import java.util.Scann er; // Needed for the Scanner class

/**
This program demonstrates a user controlled loop
*/

public class Population
{
public static void main(String[] args)
{
int startingSize = 0, dailyIncrease = 0, numberOfDays = 0;
int Temp = 0;



//Create a Scanner object for keyboard input.
Scanner Keyboard = new Scanner(System. in);


//accept initial user input here

while (startingSize < 2)
{
System.out.prin t("Please enter a number that is greater than 1 for the Population Size: ");
startingSize = Keyboard.nextIn t();
}

while (dailyIncrease < 0)
{
System.out.prin t("Enter a positive integer for the Population Size Increase: ");
dailyIncrease = Keyboard.nextIn t();
}

//do the same while loop for numberOfDays as a positive number > 0


Temp = startingSize;
dailyIncrease = dailyIncrease / 100;

for(int i = 0; i < numberOfDays; i++)
{
System.out.prin tln("Day " + i);
System.out.prin tln("Number " + Temp);
Temp = Temp * dailyIncrease;
}
}
}

[Ganon11]

This is because of the way you initialize your variables before getting input. Your while() loop will continue while population increase is less than 0, but you initialize it to 0. You should refrain from giving your variables an initial value because you are using user input for all of them.

However, if you simply declare the variables without giving them a value, your while() loops will have some trouble. Change each while() loop to a do...while() loop to fix this. Also, don't forget to add the loop for numberOfDays - currently, you don't input into it, so the loop doesn't execute at all.

[dexterdreads]

so what was the final code for the population program? Did it work?