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Why is the last dollar change calculation wrong [closed]

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Why is the last calculation printing out the wrong calculation.
here is my code:
System.out.print("Enter total cost: ");
double totalCost = input.nextDouble();
System.out.print("The Customer has paid: ");
double customerAmount = input.nextDouble();
//Calculations
double changeOwed = customerAmount - totalCost;
System.out.println("Change owed: $"+(int)changeOwed);
int amountFifty = (int)changeOwed/50;
System.out.println("How many $50 notes = " +amountFifty);
int takeAway = (int)changeOwed - (amountFifty * 50);
int amount20 = takeAway / 20;
System.out.println("How many $20 notes = " +amount20);
int amount10 = (takeAway - amount20*20) / 10;
System.out.println("How many $10 notes = " +amount10);
enter code here
int amount5 = (takeAway - amount10*10) / 5;
System.out.println("How many $5 notes = " +amount5);
int amount2 = (takeAway - amount5*5) / 2;
System.out.println("How many $2 notes = " +amount2);
int amount1 = (takeAway - amount2*2) /1;
System.out.printl
n("How many $1 notes = " +amount1);

You are not keeping track of the change you have issued along the way correctly.
int takeAway = (int)changeOwed - (amountFifty * 50);
The line above correctly calculates what's left after you determine the number of $50 bills required. This means that:
int amount20 = takeAway / 20;
int amount10 = (takeAway - amount20*20) / 10;
correctly calculates the number of $10 and $20 bills.
int amount5 = (takeAway - amount10*10) / 5;
is incorrect because you do do not subtract the values of the $20 bills, only the $10 bills. You make a similar error calculating the $2, ie. you do not account for $20 and $10. The error compounds for the $1.
You could try something like:
int amountFifty = changeOwed / 50;
double takeAway = changeOwed - (amountFifty * 50);
int amount20 = takeAway / 20;
takeAway -= (amount20 * 20);
int amount10 = takeAway / 10;
takeAway -= (amount10 * 10);
int amount5 = takeAway / 5;
takeAway -= (amount5 * 5);
int amount2 = takeAway / 2;
takeAway -= (amount2 * 2);
int amount1 = takeAway / 1;

Java compound interest calculation

my assignment is to calculate the number of years it takes to reach $5000 if you start with $2500 with 7.5% interest. The calculation should be 10 years, but it outputs 11 years. This might be a simple syntax error, but I've been trying to fix this for the past 2 hours with no luck.
final double principle = 2500.00;
double accrued = 0;
final double interest = 0.075;
int year = 0;
double interest1 = 1.0 + interest;
while (accrued < 5000.00)
{
accrued = principle * Math.pow(interest1, year);
year++;
}
System.out.printf("It would take %d years to reach at least $5000 if you start with $2,500 with 7.5%% compound interest.", year);

Try this :
final double principle = 2500.00;
double accrued = 0;
final double interest = 0.075;
int year = 0;
double interest1 = 1.0 + interest;
while (accrued < 5000.00)
{
year++;
accrued = principle * Math.pow(interest1, year);
}
System.out.printf("It would take %d years to reach at least $5000 if you start with $2,500 with 7.5%% compound interest.", year);

Troubles with a math formula - Java

I'm making a program for my java class that calculates the population for a year given the start year (2011) and increases the population by 1.2% every year. The population for 2011 is 7.000 (I'm using decimals, instead of billions). I currently have this code.
int startYear = 2011;
int endYear = user_input.nextInt();
double t = 1.2; //Population percent increase anually
double nbr = (endYear - startYear); //Number of years increased
double pStart = 7.000; //Starting population of 2011
double pEnd = pStart * Math.exp(nbr * t); // Ending population of user input
DecimalFormat nf = new DecimalFormat("2");
System.out.println("Population in " + endYear + ": " (nf.format(pEnd)));
There's no errors in the code, everything works, but I'm having troubles with the pEnd equation. Currently when I enter 2016 for the end year, i get 22824. I've tried googling a formula, but i can't find anything. Do any of you guys have an idea of the formula? If you enter 2016 for the end year, it should be around 7.433

You're incrementing by a factor of 1.2, which would represent 120% instead of 1.2%. I think what you want is :
double t = 0.012;
This change gives me an exact value of 7.4328558258175175 from 2011 to 2016.
EDIT : here's the code as requested by the author :
public static void main(String args[]){
int startYear = 2011;
int endYear = 2016;
double t = 0.012; //Population percent increase anually
double nbr = (endYear - startYear); //Number of years increased
double pStart = 7.000; //Starting population of 2011
double pEnd = pStart * Math.exp(nbr * t); // Ending population of user input
System.out.println("Population in " + endYear + ": " + pEnd);
}

Use Math.pow(1 + t / 100, nbr) instead of Math.exp(nbr * t) because you need (1+t/100)^nbr (i.e. multiply 1 + t / 100 on itself nbr times), not exp^(nbr*t):
double pEnd = pStart * Math.pow(1 + t / 100, nbr); // Ending population of user input

Try this.
double pEnd = pStart * Math.pow(1.0 + t / 100, nbr);

Converting the left over decminal to weeks, days, hours, min, seconds

Right now I am finding out 25% of a persons years and for example if you had 5 years 25% is 1.25. Though the plugin im making cant remove 1.25 years from you the .25 needs to be converted to weeks and then any leftovers to days and so on. Though I dont know how I would convert these times.
Integer y = itapi.getPlayerYears(player.getName());
Double yremove = Integer.valueOf(y) * 0.25;
Integer w = itapi.getPlayerWeeks(player.getName());
Double wremove = Integer.valueOf(w) * 0.25;
Integer d = itapi.getPlayerDays(player.getName());
Double dremove = Integer.valueOf(d) * 0.25;
Integer h = itapi.getPlayerHours(player.getName());
Double hremove = Integer.valueOf(h) * 0.25;
Integer m = itapi.getPlayerMinutes(player.getName());
Double mremove = Integer.valueOf(m) * 0.25;
Integer s = itapi.getPlayerSeconds(player.getName());
Double sremove = Integer.valueOf(s) * 0.25;
String yminus = String.valueOf(yremove) + 'y';
String wminus = String.valueOf(wremove) + 'w';
String dminus = String.valueOf(dremove) + 'd';
String hminus = String.valueOf(hremove) + 'h';
String mminus = String.valueOf(mremove) + 'm';
String sminus = String.valueOf(sremove) + 's';
ItemStack book = itapi.createTimeCard("Death of " + player.getName(), yminus + wminus + dminus + hminus + mminus + sminus, 1);
itapi.removeTime(player.getName(), yminus + wminus + dminus + hminus + mminus + sminus );
e.getDrops().add(book);
Would it be possible to work the conversion out or would it be better to convert all time to seconds then take 25% and convert it back?

I would use nested ifs and pass the remainder around. I have not tested this but it should give you an idea.
Integer y = itapi.getPlayerYears(player.getName());
double yremove = Integer.valueOf(y) *0.25;
double numWeeks = yremove * 52; //returns the number in weeks
double numDays =0;
double numHours =0;
double numMinutes =0;
double numSeconds =0;
if(numWeeks % 52 != 0){
numDays = (numWeeks % 52) * 7;
if(numDays % 7 !=0){
numHours = (numDays % 7) * 24;
if(numHours % 24 !=0){
numMinutes = (numHours % 24) * 60;
if(numMinutes % 60 !=0){
numSeconds = (numMinutes % 60) * 60;
}
}
}
}
//... then convert to string as you are already doing and pass it to removeTime()

You can use Calendar class to calculate this for you, something like:
Calendar c = Calendar.getInstance();
double millis = 1.25 * 31557600 * 1000;
long l = (long) millis;
c.setTimeInMillis(l);
System.out.println(c.get(Calendar.YEAR) + " Year");
System.out.println(c.get(Calendar.MONTH) + " months");
System.out.println(c.get(Calendar.WEEK_OF_MONTH) + " weeks");
System.out.println(c.get(Calendar.DAY_OF_MONTH) + " days");
System.out.println(c.get(Calendar.HOUR) + " hours");
System.out.println(c.get(Calendar.MINUTE) + " minutes");
System.out.println(c.get(Calendar.SECOND) + " seconds");
Output:
1971 Year
3 months
1 weeks
2 days
7 hours
0 minutes
0 seconds
Calendar defaults the starting year to 1970, you can further manipulate year and months to weeks if need be.

Create a class to manage time. This class will have methods to return time in terms of years, weeks, months, etc.
public class Time{
private long milliseconds;
public double getSeconds(){
double seconds = milliseconds/1000.0;
return seconds;
}
public void subtractSeconds(double seconds){
long millisInSeconds = (long)(seconds*1000);
this.millisecionds -= millisInSeconds;
}
//write more methods for years, months etc.
}
Then, use this class to retrieve years, months, weeks and subtract the difference. This will keep your code clean, and easy to understand.
Time time = new Time(1000*60*60);
int years = (int)time.getYears();
time.subtractYears(years);
int months = (int)time.getMonths();
time.subtractMonths(months);

Beginner Loop GUI

I have to make this GUI that is a CD calculator.
I put in the Initial investment ($): e.g. 2000
the Annual interest rate (%): e.g. (8%)
Ending value ($): e.g. 5000
The program then outputs on a jLabel: The amount of years required are "12" (e.g.)
I need to make a do while loop and a counter.
I did the get text from the 3 text fields then add the initialInvestment with the annual rate % but having trouble with the loop and the counter?
int initialInvestment, endValue, cdvalue;
double cdValue, annualDecimalConvert, annualRate;
initialInvestment = Integer.parseInt(initialInvestmentInput.getText());
annualRate = Double.parseDouble(interestRateInput.getText())/100;
endValue = Integer.parseInt(endingValueInput.getText());
cdValue = initialInvestment + (initialInvestment * annualRate);
double a = cdValue;
while (a <= endValue){
a = a++;
yearsOutput.setText("The required year needed is: " + a);
}

You're simply adding 1 to a every iteration of the loop. So it'll take a few thousand iterations that way to fullfil the loop requirements.
What you have to do is keep adding the interest every year while keeping count of the years and only update the output after you're done looping.
int initialInvestment, endValue;
double cdValue, annualDecimalConvert, annualRate;
initialInvestment = Integer.parseInt(initialInvestmentInput.getText());
annualRate = Double.parseDouble(interestRateInput.getText())/100;
endValue = Integer.parseInt(endingValueInput.getText());
// First year interest is counted here.
cdValue = initialInvestment + (initialInvestment * annualRate);
int years = 1;
while (cdValue < endValue){
cdValue = cdValue + (cdValue * annualRate);
years++;
}
yearsOutput.setText("The required year needed is: " + years);