I need these lines to output when a letter is typed instead of a whole number. I am not sure how to get it to do this: I have the code and what I need posted below if you can help me solve this issue, thank you.
This is what I am getting:
Input a valid whole number: abc
Input is not a valid number
Press any key to continue . . .
This is what I need:
Input a valid whole number: **ABC**
**ABC** is not a valid number
Press any key to continue . . .
below is what i have so far:
import java.io.PrintStream;
import java.util.Scanner;
public class FinalPractice
{
public static void main(String [] args)
{
Scanner scanner = new Scanner( System.in );
PrintStream out = System.out;
out.print( "Input a valid whole number: " );
String input = scanner.next();
int number;
try {
number = Integer.parseInt(input);
} catch (Exception e) {
out.println("Input is not a valid number");
return;
}
if (number < 0) {
out.println(number + " is not a valid number");
return;
}
printDivisors(number);
}
private static void printDivisors(int x){
PrintStream out = System.out;
for (int i=1; i<x; i++) {
if (isDivisibleBy(x, i)){
out.println(x + " is divisible by " + i);
} else {
out.println(x + " is not divisible by " + i);
}
}
}
private static Boolean isDivisibleBy(int x, int divisor){
while (x > 0) {
x -= divisor;
if (x == 0){
return true;
}
}
return false;
}
}
If I'm understanding correctly, you want your error message to include what the user actually inputted.
Change
out.println("Input is not a valid number");
to
out.println (input + " is not a valid number");
This takes your variable input, merges it with the rest of the String and it will then be displayed to the output console.
Related
This is the code:
import java.util.Scanner;
public class javapractice {
public static void main(String[] Args) {
int XX = 0;
int count = 0;
Scanner input = new Scanner(System.in);
while (true) {
System.out.println("Enter Number :");
int number = input.nextInt();
boolean nextint = input.hasNextInt();
if (nextint) {
count++;
XX += number;
} else {
break;
}
input.nextLine();
}
int YY = XX/count;
System.out.println("SUM = " + XX + " AVG = " + YY);
input.close();
}
}
I want the output to print the sum of the numbers entered and when I enter let's say a word like "Hello", it breaks out of the loop and prints Sum 0 0 and AVG = 0.
The issue I'm having is that whenever I enter the number, it asks me for it two times and doesn't take the next number in the row after that and whenever I enter a string variable lets say "I", it outputs Inputmismatch. What would be the fix to this?
Don't mix nextLine() and all the other next methods; pick one. If you want to read a line's worth of text, just call next(), but if you want the input to flow as 'everytime a user hits enter, read another token', which you usually do, update the definition of 'what defines a token?': scanner.useDelimiter("\r?\n");.
Try this code:
int XX = 0;
int count = 0;
Scanner input = new Scanner(System.in);
while (true) {
System.out.println("Enter Number: ");
if (input.hasNextInt()) {
count++;
XX += input.nextInt();
} else {
break;
}
}
int YY = XX / count;
System.out.println("SUM = " + XX + " AVG = " + YY);
input.close();
I'm trying to make a method that gets the user's input of 6 numbers and add them to a Tree set of integers. I'm trying to make a try and catch exception so if the users accidentally enters in a letter it'll catch the exception and ask them to enter in a number. Right now the program crashes when you try to enter in a letter. It'll print out "Invalid" then crashes. I'm not sure whats going on. Can anyone provide some insight?
public static Set<Integer> getTicket()
{
int userInput;
TreeSet<Integer> getNumbers = new TreeSet<Integer>();
Scanner input = new Scanner(System.in);
System.out.println("Enter your 6 numbers between 1-40: ");
for (int i = 0; i<6 ; i++)
{
try
{
System.out.print(i+1 + ": ");
userInput = input.nextInt();
}
catch (InputMismatchException e)
{
System.out.println("Invalid");
userInput = input.nextInt();
}
getNumbers.add(userInput);
}
System.out.println("Your ticket was: " + getNumbers);
return getNumbers;
}
Just a few notes on some of the changes made. From your original code, one thing I noticed that is not really an error but a head scratcher. Both of your methods (getWinning Numbers() and getTicket() ) returned a Set<integer> set, however you did not use it in main. So I simply took the output from the methods and placed them in the main method, where they should be IMHO. Methods like these should do ONE thing and in this case is return a set of integers. No printing or anything else that’s all it does.
I changed the logic in the getTicket() method. I simply set up a loop that continued until you had 6 valid numbers. Inside that loop I use a try statement to weed out the invalid input. The way the try statement is set up is one of many ways that you could accomplish this. As you can see the statement immediately after the try (guess = Integer.parseInt(userInput);) is where the invalid input problem could pop up and throw a NumberFormatException. If the input is invalid, you drop immediately to the catch where we output a message and continue. If the input is valid then we simply check for duplicates and the range of the number. If the numbers are ok then add it to pickedNumbers and increment numberCount.
public class Lottery
{
public static Set<Integer> generateWinningNumbers()
{
Random rndNumbers = new Random();
TreeSet<Integer> winningNumbers = new TreeSet<Integer>();
int max = 40;
int min = 1;
int range;
int sixNum;
for (int i = 0; i < 6; i++)
{
range = max - min + 1;
sixNum = rndNumbers.nextInt(range) + min;
while (winningNumbers.contains(sixNum))
{
sixNum = rndNumbers.nextInt(range) + min;
}
winningNumbers.add(sixNum);
}
return winningNumbers;
}
public static Set<Integer> getTicket(Scanner input)
{
String userInput;
int guess;
TreeSet<Integer> pickedNumbers = new TreeSet<Integer>();
System.out.println("Enter your 6 numbers between 1-40: ");
int numberCount = 1;
while(numberCount < 7)
{
System.out.print(numberCount + ": ");
userInput = input.nextLine();
try
{
guess = Integer.parseInt(userInput);
if( guess > 0 && guess < 41 && (!pickedNumbers.contains(guess)) )
{
pickedNumbers.add(guess);
numberCount++;
}
else
{
if (pickedNumbers.contains(guess))
{
System.out.println("Number already picked: " + guess);
}
else
{
System.out.println("Invalid number. Pick a number between 1-40: " + guess);
}
}
}
catch (NumberFormatException e)
{
// bad input
System.out.println("Invalid input: " + userInput);
}
}
return pickedNumbers;
}
}
Changes in the Main now take advantage of the methods returning a Set of integers for us. We create two Set<Integer> variables (winningTicket and userTicket) then we simply get the returned sets from the methods and output the results as opposed to printing the results from the methods.
public static void main(String[] args) throws IOException
{
Scanner userInput = new Scanner(System.in);
boolean done = false;
String yesNo;
Set<Integer> winningTicket;
Set<Integer> userTicket;
while(!done)
{
winningTicket = Lottery.generateWinningNumbers();
userTicket = Lottery.getTicket(userInput);
System.out.println("Your ticket was: " + userTicket);
System.out.println("Winning Numbers: " + winningTicket);
System.out.print("\nWould you like to try again? ");
yesNo = userInput.nextLine();
if(!yesNo.equalsIgnoreCase("y"))
{
System.out.println("Done");
done = true;
}
}
userInput.close();
}
Hope this helps
This happens because you don't catch exceptions inside cath block. for loop doesn't look good here, try while:
public static Set<Integer> getTicket()
{
int userInput;
TreeSet<Integer> getNumbers = new TreeSet<Integer>();
Scanner input = new Scanner(System.in);
System.out.println("Enter your 6 numbers between 1-40: ");
int correct = 0;
while(correct < 6)
{
try
{
System.out.print((correct+1) + ": ");
userInput = input.nextInt();
getNumbers.add(userInput);
correct++;
}
catch (InputMismatchException e)
{
System.out.println("Invalid input");
}
}
System.out.println("Your ticket was: " + getNumbers);
return getNumbers;
}
Also you cant't print collection that simple:
System.out.println("Your ticket was: " + getNumbers);
What you can do, is to use streams:
System.out.println("Your ticket was: " + getNumbers.stream().map(Object::toString).collect(Collectors.joining(" ")));
import javax.swing.*;
import java.awt.*;
public class JCD {
public static void main(String[] args) {
String input, inputs;
int input1, input2;
input = JOptionPane.showInputDialog("Enter first number");
inputs = JOptionPane.showInputDialog("Enter second number");
input1 = Integer.parseInt(input);
input2 = Integer.parseInt(inputs);
JOptionPane.showMessageDialog(null, "The GCD of two numbers " + input
+ "and" + inputs + " is: " + findGCD(input1, input2));
}// close void
private static int findGCD(int number1, int number2) {
// base case
if (number2 == 0) {
return number1;
}// end if
return findGCD(number2, number1 % number2);
}// end static
} // close class
What can I add so that it will only accept integers? If not given an integer then it will go back to ask again.....
Put your input request in a while statement, check if it's an int, if not repeat the loop, otherwise exit. Do it for both your inputs.
Something like this
public static void main(String[] args) {
String input=null, inputs=null;
int input1 = 0, input2=0;
boolean err=true;
do{
try{
input = JOptionPane.showInputDialog("Enter first number");
input1 = Integer.parseInt(input);
err=false;
}catch(NumberFormatException e){
e.printStackTrace();
}
}while(err);
err=true;
do{
try{
inputs = JOptionPane.showInputDialog("Enter second number");
input2 = Integer.parseInt(inputs);
err=false;
}catch(NumberFormatException e){
e.printStackTrace();
}
}while(err);
JOptionPane.showMessageDialog(null, "The GCD of two numbers " + input
+ "and" + inputs + " is: " + findGCD(input1, input2));
}
Note that this solution requires you to initialize your variables when you declare them
String input = null, inputs = null;
int input1=0, input2=0;
You should try with "try and catch".
input = JOptionPane.showInputDialog("Enter first number");
inputs=JOptionPane.showInputDialog("Enter second number");
try {
input1=Integer.parseInt(input);
input2=Integer.parseInt(inputs);
// establish and use the variables if the characters inserted are numbers
}
catch(NumberFormatException e){
JOptionPane.showMessageDialog(null, e+ "is not a number");
//display a warning to le the user know
}
You could use something like this :-
boolean inputAccepted = false;
while(!inputAccepted) {
try {
input1=Integer.parseInt(input);
input2=Integer.parseInt(inputs);
inputAccepted = true;
} catch(NumberFormatException e) {
JOptionPane.showMessageDialog("Please input a number only");
}
... do stuff with good input value
}
My program is to enter 10 numbers and add them together then display the result. Then I am to divide the smaller number by the larger number and display the result. Users cannot enter characters or zero.
I am new and have been working on this for DAYS. I do not see my mistake.
Now my problem is the Variable i isn't being recognized.
I introduced an Exception (try..catch) and it wouldn't read. I tried moving things all over (I'm new, I'm guessing and seeing what does what..) I did something wrong and probably something stupidly small. I need some help and fresh eyes.
I also need to end the program when the user enters 9999. Any idea where that would go? 'Cause I'm about to break out into tears.
public static void main(String[] args) throws NumberFormatException {
Scanner in = new Scanner(System.in);
Scanner input = new Scanner(System.in);
double[ ] digit = new double[11];
int sum = 0;
//Declare an array
System.out.print("Please Enter Ten Numbers:");
System.out.println();
try{
for (int i = 1; i < digit.length; i++)
System.out.print("Numbers " + i + ": ");
digit[i] = (double)in.nextInt(); //Array Not recognized here
sum += (int)digit[i];//Or recognized here
// Input the data into array from the user.
if(digit[i]==0.0)//None of these are recognized either, what did I do?
{
System.out.println("You can't enter zero. Try again");
--i; //nope
in.nextLine();//dispose of wrong number
}
}catch (NumberFormatException e){
System.out.println("You Can Only Enter Numbers!");
--i; //nope, not recognizing here either
in.nextLine();//dispose of wrong input
}
System.out.println("Total Values in Array:"+ sum);
// Calculate the sum and print the total
System.out.println();
System.out.println("Would you like to divide the values?");
System.out.println("Yes or No to Exit the Program");
String a = input.next();
if(a.equalsIgnoreCase("yes")){
double [] divisionResult = new double[digit.length / 2];
//Division array declared
for (int i = 1; i < digit.length; i += 2)
//These are all good and recognized. No problem with the division part
{
double result = digit[i];
if (result > digit[i + 1])
result = result / digit[i + 1];
else {
result = digit[i + 1] / result;
}
divisionResult [i / 2] = result;
System.out.println(result);
}
}
else if(a.equalsIgnoreCase("no")){
System.exit(0);
}
}
}
}
You for loop doesn't have braces around it. Only the first line below it is part of the loop.
You need braces around the contents of your for loop.
I have tried to modified the attached code snippet. Hope this might help you.
package com.so.general;
import java.util.Scanner;
public class AddNumbers
{
private static final int SIZE_OF_ARRAY = 10;
public static void main(String[] args)
{
int counter = 0;
double sumOfTenDigits = 0.0;
double[] digit = new double[SIZE_OF_ARRAY];
int listOfElements = digit.length;
System.out.print("Please Enter Ten Numbers:"+"\n");
Scanner readInputFromUser = new Scanner(System.in);
try
{
for (counter=0; counter<listOfElements; counter++)
{
System.out.print("Numbers " + (counter+1) + ": ");
digit[counter] = Double.parseDouble(readInputFromUser.next());
if(digit[counter] == 0.0)
{
System.out.println("Zero is not allowed. Please try again.");
System.out.print("Numbers " + (counter+1) + ": ");
digit[counter] = Double.parseDouble(readInputFromUser.next());
}
sumOfTenDigits += digit[counter];
}
}
catch(NumberFormatException numberFormatExcep)
{
System.err.println(" You have entered other than numbers. Only numbers are allowed. Terminating the program.");
numberFormatExcep.printStackTrace();
System.exit(0);
}
System.out.println("Addition is: "+ sumOfTenDigits);
System.out.println("Would you like to divide the values? Press Y to continue, any other character to terminate the program.");
Scanner continueWithDivide = new Scanner(System.in);
String userInput = continueWithDivide.nextLine();
closeScanner(readInputFromUser);
closeScanner(continueWithDivide);
if(readInputFromUser != null)
{
readInputFromUser.close();
}
// Always use static string literals on the left hand side.
// This prevents Null pointer exception.
if("Y".equalsIgnoreCase(userInput))
{
double[] divisionResult = new double[listOfElements/2];
for(int i=0; i<listOfElements; i+=2)
{
double result = digit[i];
if (result > digit[i+1])
{
result = result/digit[i+1];
}
else
{
result = digit[i+1]/result;
}
divisionResult[i/2] = result;
System.out.println(result);
}
}
else
{
System.out.println("You have entered "+userInput+". Terminating the program.");
System.exit(0);
}
}
/**
* Closed the scanner
* #param scanner
*/
public static void closeScanner(Scanner scanner)
{
if(scanner != null)
{ try
{
scanner.close();
}
catch(IllegalStateException illegatStateExcep)
{
System.err.println("Scanner is already closed.");
illegatStateExcep.printStackTrace();
}
}
}
Please note the below points:
Always use proper indentation.
Always match { }
Even if your if or for is having only one statement, use { }.
For example:
for (int counter=1; i<digit.length; i++)
{
System.out.print("Numbers " + i + ": ");
}
Above three points will save a lot of your time if some thing goes wrong in your program.
Use proper name for the variables and method.
Always close the IO resources after the use.
For example:
if(scanner != null)
{
scanner.close();
}
So, I was looking for an efficient way, using Java's standard packages, to read an input integer... For example, I came across the class "Scanner", but I found two main difficulties:
if I don't insert an int, I'm not actually able to solve the exception;
this class works with tokens, but my aim is to load the string in its full length.
This is an example of execution I would like to realize:
Integer: eight
Input error - Invalid value for an int.
Reinsert: 8 secondtoken
Input error - Invalid value for an int.
Reinsert: 8
8 + 7 = 15
And this is the (incorrect) code I tried to implement:
import java.util.Scanner;
import java.util.InputMismatchException;
class ReadInt{
public static void main(String[] args){
Scanner in = new Scanner(System.in);
boolean check;
int i = 0;
System.out.print("Integer: ");
do{
check = true;
try{
i = in.nextInt();
} catch (InputMismatchException e){
System.err.println("Input error - Invalid value for an int.");
System.out.print("Reinsert: ");
check = false;
}
} while (!check);
System.out.print(i + " + 7 = " + (i+7));
}
}
Use a BufferedReader. Check NumberFormatException. Otherwise very similar to what you have. Like so ...
import java.io.*;
public class ReadInt{
public static void main(String[] args) throws Exception {
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
boolean check;
int i = 0;
System.out.print("Integer: ");
do{
check = true;
try{
i = Integer.parseInt(in.readLine());
} catch (NumberFormatException e){
System.err.println("Input error - Invalid value for an int.");
System.out.print("Reinsert: ");
check = false;
}
} while (!check);
System.out.print(i + " + 7 = " + (i+7));
}
}
To use with tokens:
int i = Integer.parseInt(in.next());
Then you could do:
int i;
while (true) {
System.out.print("Enter a number: ");
try {
i = Integer.parseInt(in.next());
break;
} catch (NumberFormatException e) {
System.out.println("Not a valid number");
}
}
//do stuff with i
That above code works with tokens.