I have just written my first java program for a class I am taking which is used to give a student graduation information based on the credits for each class remaining. I have gotten everything to work except the required entry to check for negative values. Please see below and let me know if you have any ideas. Thanks in advance.
package txp1;
import java.util.ArrayList;
import java.util.Scanner;
public class txp1 {
public static void main(String[] args) {
// TODO code application logic here
System.out.println("Welcome to the University Graduation Calculator!");
System.out.println();
System.out.println("This calculator will help determine how many terms "
+ "you have remaining and your tuition total based upon credits"
+ " completed per semester.");
System.out.println();
double tuitionpersem = 2890;
System.out.println("We will begin by entering the number of credits for"
+ " each class remaining toward your degree.");
double sum = 0;
ArrayList<Double> credit = new ArrayList<>();
{
System.out.println("Please enter the number of credits for each individual class on a separate line and then press enter, Q to quit:");
Scanner in = new Scanner(System.in);
double number = 0;
number = Integer.parseInt(in.nextLine());
if (number <= 0);
{
System.out.println("The number of credits must be greater than zero!");
}
while (in.hasNextDouble()) {
credit.add(in.nextDouble());
}
for (int i = 0; i < credit.size(); i++) {
sum += credit.get(i);
}
System.out.println("Total credits remaining: " + sum);
}
int perterm = 0;
System.out.println("How many credits do you plan to take per term? ");
Scanner in = new Scanner(System.in);
perterm = Integer.parseInt(in.nextLine());
if (perterm <= 0);
{
System.out.println("The number of credits must be greater than zero!");
}
double totterms = sum / perterm;
totterms = Math.ceil(totterms);
System.out.print("Your remaining terms: ");
System.out.println(totterms);
double terms = (totterms);
System.out.print("The number of months to complete at this rate is: ");
System.out.println(6 * terms);
double cost = terms * 2890;
System.out.println("The cost to complete at this rate is: " + cost);
}
}
double number = 0;
number = Integer.parseInt(in.nextLine());
if (number <= 0);
The ";" at the end of if statement is the end of it. You are not doing anything with the result of number <=0. I believe you meant it to be like:
if (number <= 0){
//operations….
}
Notice that you create number of type double, then assign an int (parsed from String) to it. You can use nextDouble method to get a double directly, and if you plan this number to be an Integer anyway then use type int instead of double and nextInt instead of parsing. For more information about parsing from input, check Scanner documentation.
Your if statements terminate if you put a semi colon at the end of them. Effectively ending your logic right there. The program basically checks the condition and then moves on. Which in turn executes your second statement regardless of what number <= 0 resolves to.
//Does not get expected results
if (number <= 0);
{
//Gets executed regardless of condition
System.out.println("The number of credits must be greater than zero!");
}
//Gets expected results
if (number <= 0)
{
//Gets executed only if the condition returns true
System.out.println("The number of credits must be greater than zero!");
}
Edit: Changed due to some helpful input.
2nd Edit: I would also consider putting a loop in your code that makes the user re-enter input to get the desired value. If you put in a negative value your code will just spit the error message and keep running which can make you scratch your head. Unless your teacher isn't grading on that then forget all of what I just said. =p
Related
I'm working on a project that calculates the value of a bank account based on starting balance(b), interest rate(IR), and quarters to display. My entire code works perfectly, but the very last portion is to make sure the variables like interest rate are within the confines of the boundaries my professor gave me. I do need to display an error message if the user enters a value outside the boundaries and ask for the value again.
For example, the number of quarters to display needs to be greater than zero, and less or equal to 10.
As you can see, pretty much all of my program is in a do-while loop. I know I can have nested loops, but what would I be able to put in my do-while loop that would work in this situation? An if-else statement? Try and catch block? Another while loop?
If I used a try-catch, then could anyone give me an example of how I could do that? Thank you very much for your time, and all help is appreciated! The below is my code for reference.
import java.util.Scanner;
public class InterestCalculator
{
public static void main(String[] args)
{
Scanner scannerObject = new Scanner(System.in);
Scanner input = new Scanner(System.in);
int quartersDisplayed;
double b, IR;
do
{
Scanner keyboard=new Scanner(System.in);
System.out.println("Enter the numbers of quarters you wish to display that is greater than zero and less or equal to 10: ");
quartersDisplayed = keyboard.nextInt();
System.out.println("Next enter the starting balance. ");
System.out.println("This input must be greater than zero: ");
b = keyboard.nextDouble();
System.out.println("Finally, enter the interest rate ");
System.out.println("which must be greater than zero and less than or equal to twenty percent: ");
IR = keyboard.nextDouble();
System.out.println("You have entered the following amount of quarters: " + quartersDisplayed);
System.out.println("You also entered the starting balance of: " + b);
System.out.println("Finally, you entered the following of interest rate: " + IR);
System.out.println("If this information is not correct, please exit the program and enter the correct information.");
double quarterlyEndingBalance = b + (b * IR/100 * .25);
System.out.println("Your ending balance for your quarters is " + quarterlyEndingBalance);
System.out.println("Do you want to continue?");
String yes=keyboard.next("yes");
if (yes.equals(yes))
continue;
else
break;
}
while(true);
}
}
So here's some code to answer your questions and help get you started. However, there are problems with your logic that do not pertain to your question which I will address afterward.
Note: I have added comments to your code. Most of them start with "EDIT:" so that you can tell what I changed. I didn't use this prefix in all cases because some of it is new code and it's obviously my comment
import java.util.Scanner;
public class InterestCalculator {
public static void main(String[] args) {
// EDIT: you already have a scanner defined below with a more meaningful name so I removed this one
// Scanner scannerObject = new Scanner(System.in);
Scanner input = new Scanner(System.in);
//EDIT: defining userResponse outside the loop so we can use it everywhere inside
String userResponse = null;
do {
//EDIT: moved the variables inside the loop so that they are reset each time we start over.
//EDIT: initialize your variable to a value that is invalid so that you can tell if it has been set or not.
int quartersDisplayed = -1;
//EDIT: gave your variables more meaningful names that conform to java standards
double startingBalance = -1, interestRate = -1;
//EDIT: you don't need a second Scanner, just use the one you already have.
// Scanner keyboard = new Scanner(System.in);
do{
System.out.println("Enter the numbers of quarters you wish to display that is greater than zero and less or equal to 10: ");
userResponse = input.next();
try{
quartersDisplayed = Integer.parseInt(userResponse);
}catch(NumberFormatException e){
//nothing to do here, error message handled below.
}
if(quartersDisplayed <= 0 || quartersDisplayed > 10){
System.out.println("Sorry, that value is not valid.");
}else{
break;
}
}while(true);
do{
System.out.println("Enter the starting balance (must be greater than zero): ");
userResponse = input.next();
try{
startingBalance = Double.parseDouble(userResponse);
}catch(NumberFormatException e){
//nothing to do here, error message handled below.
}
if(startingBalance <= 0){
System.out.println("Sorry, that value is not valid.");
}else{
break;
}
}while(true);
do{
System.out.println("Enter the interest rate (greater than zero less than twenty percent): ");
userResponse = input.next();
try{
interestRate = Double.parseDouble(userResponse);
}catch(NumberFormatException e){
//nothing to do here, error message handled below.
}
//Note: I assume twenty percent is represented as 20.0 here
if(interestRate <= 0 || interestRate > 20){
System.out.println("Sorry, that value is not valid.");
}else{
break;
}
}while(true);
System.out.println("You have entered the following amount of quarters: "
+ quartersDisplayed);
System.out.println("You also entered the starting balance of: " + startingBalance);
System.out.println("Finally, you entered the following of interest rate: "
+ interestRate);
System.out.println("If this information is not correct, please exit the program and enter the correct information.");
double quarterlyEndingBalance = startingBalance + (startingBalance * interestRate / 100 * .25);
System.out.println("Your ending balance for your quarters is "
+ quarterlyEndingBalance);
System.out.println("Do you want to continue?");
//EDIT: modified your variable name to be more meaningful since the user's response doesn't have to "yes" necessarily
userResponse = input.next();
// EDIT: modified the logic here to compare with "yes" or "y" case insensitively.
// if (userResponse.equals(userResponse))
if("y".equalsIgnoreCase(userResponse) || "yes".equalsIgnoreCase(userResponse))
continue;
else
break;
} while (true);
Now to address other issues - your interest calculation doesn't seem correct to me. Your formula does not make use of the quartersDisplayed variable at all. I assume you're compounding the interest quarterly so you will definitely need to make use of this when calculating your results.
This may be beyond the scope of your project, but you should not use double or float data types to represent money. There is a stackoverflow question about this topic that has good information.
Possible improvements - since you're asking the user for two values of type double you could create a method to ask for a double value and call it twice instead of repeating the code. This is a better approach because it helps reduce the chance of mistakes and makes testing and maintenance easier.
You can do something like this in your do/while loop:
do
{
Scanner keyboard = new Scanner(System.in);
do
{
System.out.println("Enter the numbers of quarters you wish to display that is greater than zero and less or equal to 10: ");
quartersDisplayed = keyboard.nextInt();
}
while (quartersDisplayed < 1 || quartersDisplayed > 10);
System.out.println("Next enter the starting balance. ");
do
{
System.out.println("This input must be greater than zero: ");
b = keyboard.nextDouble();
}
while (b < 1);
// rest of code ...
}
With the Scanner#hasNextInt (and the equivalent for double), you can avoid having exceptions thrown, and thus don't need try-catch clauses. I think in general if you can avoid try-catch, it's good, because they are clumsy - but I might be wrong.
However, my approach is like this. Inside your outer do-while, have three other do-while-loops to get the three values. The reason is that you want to keep looping until you get a correct value. The explanation of why keyboard.nextLine() is important is covered here.
I didn't include all of your code, only the part in question. Here's my take on it:
import java.util.Scanner;
public class InterestCalculator {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
int quartersDisplayed = -1;
double b = -1.0;
double IR = -1.0;
do {
do {
System.out.println("Enter the number of quarters.");
if(keyboard.hasNextInt()) {
quartersDisplayed = keyboard.nextInt();
keyboard.nextLine(); //important
} else {
System.out.println("You need to enter an integer.");
continue;
}
} while(quartersDisplayed < 1 || quartersDisplayed > 10);
do {
System.out.println("Enter the starting balance.");
if(keyboard.hasNextDouble()) {
b = keyboard.nextDouble();
keyboard.nextLine();
} else {
System.out.println("You must enter a number.");
continue;
}
} while(b <= 0);
do {
System.out.println("Enter the interest rate.");
if(keyboard.hasNextDouble()) {
IR = keyboard.nextDouble();
keyboard.nextLine();
} else {
System.out.println("You must enter a number.");
continue;
}
} while(IR <= 0 || IR > 20.0);
//... rest of code
} while(true);
}
}
I've written a portion of code to take a user input, match it to a string value and then use a related double value to make calculations:
double [] currency = new double[] {0.05,0.10,0.20,0.50,1.00,2.00,5.00,10.00,20.00,50.00,100.00};
String [] currencytext = {"$0.05","$0.10","$0.20","$0.50","$1.00","$2.00","$5.00","$10.00","$20.00","$50.00","$100.00"};
Scanner keyboard = new Scanner(System.in);
for (int i = 0; i < currencytext.length; i++) {
boolean valid = false;
while(!valid){
System.out.format("$%.2f remains to be paid. Enter coin or note: ",sum);
String payment = keyboard.next();
if(payment.equals(currencytext[i])){
sum = sum - currency[i];
if(sum == 0) {
System.out.print("You gave " + payment);
System.out.print("Perfect! No change given.");
System.out.print("");
System.out.print("Thank you" + name + ".");
System.out.print("See you next time.");
}
}
if(!(payment.equals(currencytext[i]))) {
System.out.print("Invalid coin or note. Try again. \n");
}
if(payment.equals(currencytext[i]) && currency[i] > sum){
System.out.print("You gave " + payment);
System.out.print("Your change:");
}
}
}
The problem is that when it gets to user input, it doesn't match any string values except for $0.05. It seems to me like its not iterating through the array properly but I can't figure out why. Is anyone able to see a problem here?
This is a possible solution for your problem
Scanner keyboard = new Scanner(System.in);
double [] currency = new double[] {0.05,0.10,0.20,0.50,1.00,2.00,5.00,10.00,20.00,50.00,100.00};
String [] currencytext = {"$0.05","$0.10","$0.20","$0.50","$1.00","$2.00","$5.00","$10.00","$20.00","$50.00","$100.00"};
String payment = keyboard.next();
double sum = 100; // <- Working example - Read sum from keyboard entry
while (sum > 0) {
boolean paymentFound = false;
for (int i = 0; i < currencytext.length; i++) {
if (payment.equals(currencytext[i])) {
sum = sum - currency[i];
paymentFound = true;
if (sum == 0) {
System.out.println("You gave " + payment);
System.out.println("Perfect! No change given.");
// System.out.print("Thank you" + name + ".");
System.out.println("See you next time.");
break;
} else if (sum < 0) {
System.out.println("You gave " + payment);
System.out.println("Your change:" + (-1 * sum));
break;
}
}
}
if (!paymentFound) {
System.out.println("Invalid coin or note. Try again. \n");
}
if (sum > 0) {
System.out.format("$%.2f remains to be paid. Enter coin or note: ", sum);
payment = keyboard.next();
}
}
while-loop will continue until the payment is fullfilled.
for-loop traverse the arrays until a suitable payment is found
If suitable payment is found we substract it from sum. We use break to exit the for-loop in both cases. There is no need to keep searching.
If no suitable payment is found [!paymentFound], we keep on asking.
if (!paymentFound) {
System.out.println("Invalid coin or note. Try again. \n");
}
if (sum > 0) {
System.out.format("$%.2f remains to be paid. Enter coin or note: ", sum);
payment = keyboard.next();
}
The program will end when (sum < 0), in which case the while-loop exits.
I have use println instead of print to improve message legibility.
Too many flaws to point out.
However,
When the currencytext[i] does not match payment, it executes this code:
System.out.print("Invalid coin or note. Try again. \n");
System.out.format("$%.2f remains to be paid. Enter coin or note: ",sum);
payment = keyboard.next();
So, it executes this for all the times that your input does not match currencytext[i].
And, in this block, you have
payment = keyboard.next();
So, it asks for new input, in this block itself. Hence, you get the said output for all inputs except $0.05.
As far as $0.05 is concerned, your first if block executes successfully, and prints no output. So, it moves to the next iteration of the while loop, where again, payment remains the same ($0.05), but currencytext[i] becomes $0.10. SO they do not match, and you get the said output.
How to correct this:
With this code, you need to do a lot of corrections.
I suggest you again start from scratch.
If it doesn't fit, it sets valid to true, so the code just has the chance to check against the first item at currencytext[0], which is $0.05. Then !payment.equals(currencytext[i]) is also true, and your code prints the lines there. Your else ifs are also not properly nested.
I don't know how you are reading input. One improvement you can do is write reading input code in for loop.
Scanner scanner = new Scanner(System.in);
for (... ) {
....
String payment = scanner.nextLine();
....
}
I'm working on an assignment where I need to ask the user for console input for how many items they have, then ask them for two integers (earned and max possible) which I can then calculate the weighted average. It needs to be done with a loop, not an array for this assignment. I have figured out how to gather the number of items and one of the integers, but I don't know how to gather multiple integers within a for loop. Here's the method I have so far:
public static void homework() {
Scanner console = new Scanner(System.in);
System.out.print("Number of assignments? ");
int totalAssignments = console.nextInt();
int sum = 0;
for (int i = 1; i <= totalAssignments; i++) {
System.out.print(" #" + i + "? ");
int next = console.nextInt();
sum += next;
}
System.out.println();
System.out.println("sum = " + sum);
}
I am able to tally the sum of earned scores with this method, but not the maximum possible scores so that I can take a weighted average.
Thanks!
You need to read the user input (only) integers in a loop and sum each values(weighted and score). You could return one of the sums with something like the following:
public int returnSum() {
Scanner keyboard = new Scanner(System.in);
boolean isValid = false;
int sum1;
while (*NotAtEndOfInput or Some Condition to Signal End of Input*) {
System.out.print("Please enter score: ");
try {
num = keyboard.nextInt();
sum1+=num;
} catch (InputMismatchException ex) {
//In case user enters anything else than integer, catch
//the exception and let the program move ahead to let the user enter again.
System.out.println("Wrong input. Ony integer input will be processed.");
//discards anything which is not int
keyboard.nextLine();
}finally{
//close input stream to avoid memory leak.
keyboard.close();
}
}
return sum1;
}
You will need to read and sum the other number similarly. Hope this helps.
User inputs numbers one by one and then once they type in an invalid number (has to be from 1-200) the program calculates the average of the numbers that were inputted.
I'm just wondering what would the code be for this. I know the one for inputting one piece of data. Example would be:
`Scanner in = new Scanner(System.in);
String numberOfShoes = "";
System.out.println("Enter the number of shoes you want: (0-200) ");
numberOfShoes = in.nextLine();`
this is just an example, but this time I want the user to input a lot of numbers. I know I'm going to include a loop somewhere in this and I have to stop it once it contains an invalid number (using a try catch block).
* I would also like to add that once the user inputs another number it always goes to the next line.
Just use a while loop to continue taking input until a condition is met. Also keep variables to track the sum, and the total number of inputs.
I would also suggest having numberOfShoes be an int and use the nextInt() method on your Scanner (so you don't have to convert from String to int).
System.out.println("Enter your number of shoes: ");
Scanner in = new Scanner(System.in);
int numberOfShoes = 0;
int sum = 0;
int numberOfInputs = 0;
do {
numberOfShoes = in.nextInt();
if (numberOfShoes >= 1 && numberOfShoes <= 200) { // if valid input
sum += numberOfShoes;
numberOfInputs++;
}
} while (numberOfShoes >= 1 && numberOfShoes <= 200); // continue while valid
double average = (double)sum / numberOfInputs;
System.out.println("Average: " + average);
Sample:
Enter your number of shoes:
5
3
7
2
0
Average: 4.25
It added 5 + 3 + 7 + 2 to get the sum of 17. Then it divided 17 by the numberOfInputs, which is 4 to get 4.25
you are almost there.
Logic is like this,
Define array
Begin Loop
Accept the number
check if its invalid number [it is how u define a invalid number]
if invalid, Exit Loop
else put it in the array
End Loop
Add all numbers in your array
I think you need to do something like this (which #Takendarkk suggested):
import java.util.Scanner;
public class shoes {
public void main(String[] args){
int input = 0;
do{
Scanner in = new Scanner(System.in);
String numberOfShoes = "";
System.out.println("Enter the number of shoes you want: (0-200) ");
numberOfShoes = in.nextLine();
input = Integer.parseInt(numberOfShoes);
}while((input>=0) && (input<=200));
}
}
you can use for loop like this
for(::)
{
//do your input and processing here
if(terminating condition satisified)
{
break;
}
}
I am trying to validate a user input, cuPerTerm > 12
I get the error message but the program continues and uses the invalid input to run
package gradplanner;
import java.util.Scanner;
public class GradPlanner {
int cuToComp;
int cuPerTerm;
public static void main(String[] args) {
final double COST = 2890.00; //flat-rate tuition rate charged per term
final int MONPERTERM = 6; //number of months per term
int cuToCompTotal = 0;
int numTerm;
int numMonToComp;
double tuition;
//prompt for user to input the number of CUs for each individual course remaining.
Scanner in = new Scanner(System.in);
System.out.print("Please enter the number of CUs for each individual course you have remaining, Entering a - number when finished. ");
int cuToComp = in.nextInt();
//add all CUs from individual courses to find the Total number of CUs left to complete.
while (cuToComp > 0)
{
cuToCompTotal += cuToComp;
System.out.print("Please enter the number of CUs for each individual course you have remaining, Entering a - number when finished. ");
cuToComp = in.nextInt();
}
System.out.println("The total number of CUs left is " + cuToCompTotal);
//prompt for user to input how many CUs they plan to take per term.
System.out.print("How many credit units do you intend to take per term? ");
int cuPerTerm = in.nextInt();
if (cuPerTerm <12) //validate input - Undergraduate Students Must enroll in a minimum of 12 CUs per term
{
System.out.print("Undergraduate Students must enroll in a Minimum of 12 CUs per Term. ");
}
//Calculate the number of terms remaining, if a remain is present increase number of terms by 1.
numTerm = cuToCompTotal/cuPerTerm;
if (cuToCompTotal%cuPerTerm > 0)
{
numTerm = numTerm + 1;
}
System.out.println("The Number of Terms you have left is " + numTerm + " Terms. ");
//Calculate the number of Months left to complete
numMonToComp = numTerm * MONPERTERM;
System.out.println("Which is " + numMonToComp + " Months. ");
//calculate the tuition cost based on the number of terms left to complete.
tuition = numTerm * COST;
System.out.println("Your Total Tuition Cost is: " + "$" + tuition +" . ");
}
}
I need it to continue to re-ask until 12 or something greater is entered. and then continue the program.
You should use a while loop so that you continue looping until cuPerTerm is at least 12. Remember to take the user input again with cuPerTerm = in.nextInt(); inside the while loop.
Here's a simple solution:
int cuPerTerm = -1; // intialize to an invalid value
while (cuPerTerm < 12) {
System.out.print("How many credit units do you intend to take per term? ");
int cuPerTerm = in.nextInt();
if (cuPerTerm <12) { //validate input - Undergraduate Students Must enroll in a minimum of 12 CUs per term
System.out.print("Undergraduate Students must enroll in a Minimum of 12 CUs per Term. ");
}
}
Add this to continue getting input till it satisfies your condition:
while(cuPerTerm <= 12){
//Ask use to provide input
}
It is simple while loop which checks your input condition and continues taking input till it is satisfied.
Edit: -
Initialize your cuPerTerm =0
while(cuPerTerm <= 12)
{
System.out.print("Please enter the number of CUs for each individual course you have remaining, Entering a - number when finished. ");
int cuToComp = in.nextInt();
}
There are pitfalls: Simple doing scanner.nextInt() will give you the next Integer of the CURRENT Line.
If the user types in test, nextInt() will throw an InputMismatchException, you have to handle. Also the int will NOT be consumed
So you have to call scanner.nextLine() in between to Clean the current (mismatched) result.
All together something like this:
do{
try
{
System.out.print("Enter number > 12: ");
System.out.flush();
number = scanner.nextInt();
if (number > 12)
done = true;
}
catch(InputMismatchException e) {
System.out.println("This is not a number");
scanner.nextLine() //!Important!
}
}while(!done);
I think that a do-while loop will best suit your needs:
int val;
do {
val = in.nextInt();
} while (val < 12);