Hello I am stuck on a programming assignment for class. The assignment is to make a program that can count different loops. I have the prompt user input code correct I think I just can't figure out how to make it print my message the amount of times that I have entered.
I want the second while loop to print something like
Row 1 - Hello
Row 2 - Hello
Row 3 - Hello
Row 4 - Hello
For the number that I put as the input.
Thank you for the help in advance.
import java.util.Scanner;
public class CountingLoops
{
public static void main(String[] args)
{
String message; // First message prompt
String inputString; // For reading input.
double numRows; // Number to be asked.
double rowNumber = 1;
Scanner keyboard = new Scanner(System.in);
System.out.print("Enter the message you want to print? ");
message = keyboard.nextLine();
System.out.print("Enter how many times you want your message to be printed. Enter the value from 1-20:" );
numRows = keyboard.nextDouble();
while (numRows > 20 || numRows < 1)
{
System.out.print("Number was not between 1-20. Try Again.");
System.out.print("Enter how many times you want your message to be printed. Enter the value from 1-20: ");
numRows = keyboard.nextDouble();
}
while (numRows <= 20)
{
System.out.println("Row " + rowNumber++ + " - " + message);
rowNumber = keyboard.nextDouble();
rowNumber++;
}
}
}
What do you mean by "a program that can count different loops". Currently the bottom while loop is an infinite loop since numRows isn't being updated. Here's what I believe can solve your issue:
while (numRows > 0)
{
System.out.println("Row " + rowNumber++ + " - " + message);
rowNumber++;
numRows--;
}
Since it is an assignment, I won't provide the code. But all the problem with your code is in the last while loop.
First, you don't even change the value of the variable numRows and of course, you cannot exit the while loop.
Second, you don't need to read another input during this while loop since all the input is done at the beginning.
Third, you added rowNumber twice in your code and obviously, it is incorrect and it should be changed to something else.
Your answer will involve comparing rowNumber and numRows to determine when you are done.
Related
I'm using NetBeans 8.2 on Ubuntu. Is there any way to make s.hasNextDouble() returns false using keyboard input, so that the last line of the code is executed, without changing the code?
This code snippet calculates the average of the entered numbers.
double sum = 0;
int n = 0;
Scanner s = new Scanner(System.in);
System.out.print("Enter 1 number: ");
while (s.hasNextDouble()) {
double number = s.nextDouble();
sum += number;
n++;
System.out.print("Enter " + (n + 1) + " number: ");
}
System.out.println();
if (n == 0) {
System.out.println("Error!!!");
} else {
System.out.println("Average: " + sum / n);
}
hasNextDouble returns false if the next token can't be interpreted as a double, so you can break that loop by entering something that's not a number. This could be anything like for example x, abc or !.
An example of running the program would be:
Enter 1 number: 3
Enter 2 number: 6
Enter 3 number: x
Average: 4.5
Process finished with exit code 0
You could change the message to something like:
System.out.print("Enter " + (n + 1) + " number, or anything else to end: ");
So, there are different ways to do this.
First way, the nearest to yours, is to simulate EOF with pressing CTRL+D as mentioned here
How to send EOF via Windows terminal
(I've tried, it realy works)
Second way is to think about some flag. For example, read until your number isn't -1 or SIMPLY ENTER SOME CHARACTER or something NOT DOUBLE or INT.
Third way is to read line by line, separate numbers using String[] nums = yourLine.split("\\s"); and than just go through your splited string array until Double.parseDouble(nums[i]) will throw exception
That's ways i could remember now. Good luck ;)
Hi I was wondering if I could get some help with a GPA calculator.
What it needs to do is:
The input will consist of a sequence of terms, e.g., semesters.
The input for each term will consist of grades and credits for courses taken within that term.
For each term, the user will type in an integer that represents the number of courses
taken within that term.
Each course is specified by a String letter grade and an int number of credits, in that order, separated by white space. 5. If the user types in -1 for the number of courses taken in a term, then the program must print a final overall summary and then terminate.
DO NOT prompt for any input. Thus, after you run your program in BlueJ, type Ctrl-T to force the Terminal window to pop up.
As always, follow the input / output format depicted in the Sample runs section.
Shown below is the error message I get and the code I have, thank you for any assistance in advance or tips I could try.
Terminal window and error message:
import java.util.Scanner;
/*
*
*
*/
public class Prog2 {
public static void main(String args[]) {
Scanner numberInput = new Scanner(System.in);
int numberofClasses = numberInput.nextInt();
Scanner input = new Scanner(System.in);
String [] grade = new String[5];
int [] credit = new int [5];
double totalCredit = 0.0;
double realGrade = 0.0;
double result = 0.0;
while (numberofClasses > 0)
{
for (int x = 0; x < numberofClasses; x++ )
{
grade[x] = input.next();
credit[x] = input.nextInt();
}
for(int x=0;x < numberofClasses; x++ ){
if(grade[x].equals("A+")){
realGrade=4.0;
}
else if(grade[x].equals("A")){
realGrade=4.0;
}
else if(grade[x].equals("A-")){
realGrade=3.67;
}
else if(grade[x].equals("B+")){
realGrade=3.33;
}
else if(grade[x].equals("B")){
realGrade=3.00;
}
else if(grade[x].equals("B-")){
realGrade=2.67;
}
else if(grade[x].equals("C+")){
realGrade=2.33;
}
else if(grade[x].equals("C")){
realGrade=2.00;
}
else if(grade[x].equals("C-")){
realGrade=1.33;
}
result = result+realGrade*credit[x];
totalCredit=totalCredit+credit[x];
}
System.out.println("Summary for term:");
System.out.println("----------------------------------");
System.out.println("Term total grade points: " + result);
System.out.println("Term total credits:" + totalCredit);
System.out.println("GPA:"+result/totalCredit);
}
// This block is getting used later please ignore
System.out.println("Final Summary:");
System.out.println("----------------------------------");
System.out.println(" Overall terms");
System.out.println(" Total grade points: " + result);// this needs to be all );
System.out.println(" Total credits" + totalCredit);//This needs to be all );
System.out.println("Cumulative GPA:"+result/totalCredit);
}
}
When your while loop ends, numberofClasses still contains the value that was entered before the while loop started the first time. Specifically, after you output the line:
GPA=3.0588...
you hit the end of the loop, then return to:
while (numberofClasses > 0)
which is true. The next "3" that you enter doesn't go into numberofClasses, it is picked up by
grade[x] = input.next();
Then the "A" is picked up by
credit[x] = input.nextInt();
which throws an exception since it's not an integer.
All you need to do is ask for the number of classes again at the end of the while loop:
System.out.println("GPA:"+result/totalCredit);
numberofClasses = numberInput.nextInt();
}
Output:
5
A 3
B 2
C 4
A 5
C 3
Summary for term:
----------------------------------
Term total grade points: 52.0
Term total credits:17.0
GPA:3.0588235294117645
3
A 3
B 5
C 1
Summary for term:
----------------------------------
Term total grade points: 81.0
Term total credits:26.0
GPA:3.1153846153846154
i recommend looking into whether your compiler or IDE has a "debug" feature. It is a very helpful tool, and lets you watch how your program goes through your code
Just a tip...
When you ask for input, print what you're asking for first. When I launched your program I had no idea what to do. Try adding System.out.println("input number of classes you took");before you prompt for that number.
Here is what is wrong. (If you printed what you're asking for first, this would be more apparent).
after your program displays the stats, you enter 5. Yet your program is actually still on this line grade[x] = input.next(); on line 22 i believe.
when you enter 5, your scanner is expecting a letter. and an exception is thrown.
you need to consider how you escape this loop here. while (numberofClasses > 0) perhaps use an if statement? otherwise your program loops for forever, never asking for a new class number
Total newbie here, please forgive the silly question. As an exercise I had to make a program (using do and while loops) that calculates the average of the numbers typed in and exits when the user types 0. I figured the first part out :) The second part of the exercise is to change the program to display an error message if users types 0 before typing any other number. Can you kindly explain to me what is the easiest way to accomplish this? If you provide the code is great but I’d also like an explanation so I am actually understanding what I need to do.
Thank you! Here is the code:
import java.util.Scanner;
public class totalave1 {
public static void main(String[] args) {
int number, average, total = 0, counter = 0;
Scanner fromKeyboard = new Scanner(System.in);
do {
System.out.println("Enter number to calculate the average, or 0 to exit");
number = fromKeyboard.nextInt();
total = total + number;
counter = counter + 1;
average = (total) / counter;
} while (number != 0);
System.out.println("The average of all numbers entered is: " + average);
}
}
The second part of the exercise is to change the program to display
an error message if users types 0 before typing any other number.
It is not very clear :
Do you you need to display a error message and the program stops ?
Do you you need to display a error message and to force the input to start again ?
In the first case, just add a condition after this instruction : number=fromKeyboard.nextInt(); :
do{
System.out.println("Enter number to calculate the average, or 0 to exit");
number=fromKeyboard.nextInt();
if (number == 0 && counter == 0){
System.out.println("Must not start by zero");
return;
}
...
} while (number!=0);
In the second case you could pass to the next iteration to take a new input.
To allow to go to next iteration, just change the number from zero to any value different from zero in order that the while condition is true.
do{
System.out.println("Enter number to calculate the average, or 0 to exit");
number=fromKeyboard.nextInt();
if (number == 0 && counter == 0){
System.out.println("Must not start by zero");
number = 1;
continue;
}
...
} while (number!=0);
The good news is that you probably have done the hardest part. :) However, I don't want to give too much away, so...
Have you learned about control flow? I assume you might have a little bit, as you are using do and while. I would suggest taking a look at the following Java documentation first: https://docs.oracle.com/javase/tutorial/java/nutsandbolts/if.html
Then, look at your current solution and try to think what conditions you have that would lead you to display the error message, using if statements. How do you know the user typed a 0? How do you know it's the first thing they entered? Are there any variables that you have now that can help you, or do you need to create a new one?
I know this is not a code answer, but you did well in this first part by yourself already. Let us know if you need further hand.
Don't go down code after reading and if you cant then see the code.
First you have to learn about the flow control. Second you have to check whether user entered 0 after few numbers get entered or not, for that you have to some if condition. If current number if 0 and it is entered before anyother number then you have to leave rest of the code inside loop and continue to next iteration.
import java.util.Scanner;
public class totalave1
{
public static void main (String[]args)
{
int number, average, total=0, counter=0;
boolean firstTime = true;
Scanner fromKeyboard=new Scanner (System.in);
do{
System.out.println("Enter number to calculate the average, or 0 to exit");
number=fromKeyboard.nextInt();
if(firstTime && number==0){
System.out.println("error enter number first");
number = -1;
continue;
}
firstTime = false;
total=total+number;
counter=counter+1;
average=(total)/counter;
} while (number!=0);
System.out.println("The average of all numbers entered is: "+average);
}
}
Here is a simple program that extends on yours but uses nextDouble() instead of nextInt() so that you can enter numbers with decimal points as well. It also prompts the user if they have entered invalid input (something other than a number):
import java.util.Scanner;
class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Java_Paws's Average of Numbers Program");
System.out.println("======================================");
System.out.println("Usage: Please enter numbers one per line and enter a 0 to output the average of the numbers:");
double total = 0.0;
int count = 0;
while(scanner.hasNext()) {
if(scanner.hasNextDouble()) {
double inputNum = scanner.nextDouble();
if(inputNum == 0) {
if(count == 0) {
System.out.println("Error: Please enter some numbers first!");
} else {
System.out.println("\nThe average of the entered numbers is: " + (total / count));
break;
}
} else {
total += inputNum;
count++;
}
} else {
System.out.println("ERROR: Invalid Input");
System.out.print("Please enter a number: ");
scanner.next();
}
}
}
}
Try it here!
import java.util.Scanner;
public class LoveCS
{
public static void main(String[] args)
{
int noTimesPrinted;
Scanner scan = new Scanner(System.in);
System.out.print("How many times should the message be printed: ");
noTimesPrinted = scan.nextInt();
int count = 1;
while (count <= noTimesPrinted)
{
System.out.println(" I love Computer Science!!");
count++;
}
}
}
Instead of using constant LIMIT, ask the user how many times the message should be printed. You will need to declare a variable to store the user’s response and use that variable to control the loop. (Remember that all caps is used only for constants!)
I HAVE COMPLETED PART1. I AM STUCK ON PART2. How do I get the number sequence??
Number each line in the output, and add a message at the end of the loop that says how many times the message was printed. So if the user enters 3, your program should print this:
1 I love Computer Science!!
2 I love Computer Science!!
3 I love Computer Science!!
Printed this message 3 times.
If the message is printed N times, compute and print the sum of the numbers from 1 to N.
So for the example above, the last line would now read:
Printed this message 3 times. The sum of the numbers from 1 to 3 is 6.
Note that you will need to add a variable to hold the sum.
You have a few choices. You could use String concatenation,
int count = 1;
while (count <= noTimesPrinted)
{
System.out.println(Integer.toString(count) + " I love Computer Science!!");
count++;
}
System.out.println("Printed this message " + noTimesPrinted + " times");
Or with printf and (since you said you wanted a for loop) something like
for (int count = 1; count <= noTimesPrinted; count++) {
System.out.printf("%d I love Computer Science!!%n", count);
}
System.out.printf("Printed this message %d times%n", noTimesPrinted);
I am writing a simple bank application. In my program I have used a while loop. In case a user enters wrong input it will re-prompt to enter again.
Now the problem is I am not able to write any system.out.print statement after the loop. It always shows error (says: unreachable statement), and eventually the line doesn't get printed out.
HOW CAN I FIX THIS?
[The reason I need to use system.out.print because I want to print all the info the user has input.]
The program I am working on:
package bankapplication;
import java.util.Scanner;
public class BankApplication {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("WELCOME TO OUR BANK!\n\nPlease give all the inofrmation correctly.");
System.out.println("Enter your name: ");
String name = input.nextLine();
System.out.println("");
System.out.println("Enter your SSN: ");
String ssn = input.next();
System.out.println("");
System.out.println("Enter your Address: ");
String address = input.next();
System.out.println("");
System.out.println("Enter your telephone nr: ");
String teleNum = input.next();
System.out.println("");
while (true) {
System.out.println("Choose an account number for you (Between 5 and 10 positive numbers): ");
int accNum = input.nextInt();
System.out.println("");
if (accNum < 0 && accNum > 10 && accNum < 6) {
System.out.println("Invalid choise!");
} else {
System.exit(0);
}
}
System.out.println("Congratulation! Your new account has been created!");
System.out.println("The following is your account info:\n");
System.out.println("name: " + name + "SSN: " + ssn + "Address: " + address + "Tele. Num: " + teleNum + "Acc num: " + accNum);
}
}
When you invoke System.exit the entire program exits and the process is terminated. Instead you could replace the else statement with:
else { break; }
That will break the current loop and the rest of the statements will be printed. The keyword break simply breaks the loop.
You have a while (true) loop - a loop which is infinite unless something in the loop breaks out of it. The only line you have that breaks out of the loop is System.exit(0), which will end your program entirely. Therefore it is impossible to reach the code after your loop.
If you mean to break out of the loop in your else clause, use a break statement instead of exiting the program.
Note however that your if condition will never be true.
if (accNum < 0 && accNum > 10 && accNum < 6) {
accNum can never be less than zero and greater than 10.
You need to figure out what condition you actually want to check.
the condition
(accNum < 0 && accNum > 10 && accNum < 6)
can never be acheived , there is no way a number can be negative and >10 at the same time...the System.exit(0) will always be called on first loop.
That and when u call System.exit(0) you are exiting the program not the loop, therefor you will never reach the statement you are talking about .
you should either use
break;
or if you would like more prestige, put the right condition in the while(condition) ... try not to get used to using break ;