I wrote a simple program.it gets two Integer number from user and return odd numbers to user.i validate them to force the user to type just Integer numbers.
when user type other data type,program gives him my custom error.that is right up to now but when this happen user has to type inputs from the beginning.it means that program takes the user to the first home.
here is my main class :
package train;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Calculate cal = new Calculate();
Scanner input = new Scanner(System.in);
int number1 = 0;
int number2 = 0;
boolean isNumber;
do {
System.out.println("enter number1 please : ");
if (input.hasNextInt()) {
number1 = input.nextInt();
isNumber = true;
System.out.println("enter number2 please : ");
}
if (input.hasNextInt()) {
number2 = input.nextInt();
isNumber = true;
} else {
System.out.println("wrong number!");
isNumber = false;
input.next();
}
} while (!(isNumber));
cal.setNumbers(number1, number2);
cal.result();
input.close();
}
}
and here is my calculate class which return odd numbers :
public class Calculate {
private int minNumber;
private int MaxNumber;
public void setNumbers(int min, int max) {
this.minNumber = min;
this.MaxNumber = max;
}
public void result() {
int count = 0; // number of results
ArrayList<Integer> oddNumber = new ArrayList<Integer>(); // array of odd numbers
// get odd numbers
for (int i = minNumber; i < MaxNumber; i++) {
if ((i % 2) != 0) {
oddNumber.add(i);
count++;
}
}
int i = 0;// counter for printing array
while (i < oddNumber.size()) {
if(i != oddNumber.size()){
System.out.print(oddNumber.get(i) + ",");
}else{
System.out.println(oddNumber.get(i));
}
i++;
}
// print result numbers
System.out.println("\nResult number : " + count);
// print number range
System.out.println("You wanted us to search between " + minNumber
+ " and " + MaxNumber);
}
}
Create a method verifyAndGetNumber which will verify a number with regex \d+ which means match one or more digit. Throw Exception if it is not number. Catch the exception and print your custom message.
public static void main(String[] args) {
Calculate cal = new Calculate();
Scanner input = new Scanner(System.in);
int number1 = 0;
int number2 = 0;
boolean isNumber = false;
do {
try {
System.out.println("enter number1 please : ");
if (input.hasNextLine()) {
number1 = verifyAndGetNumber(input.nextLine());
}
System.out.println("enter number2 please : ");
if (input.hasNextLine()) {
number2 = verifyAndGetNumber(input.nextLine());
}
isNumber = true;
} catch (Exception e) {
System.out.println(e.getMessage());
}
} while (!isNumber);
cal.setNumbers(number1, number2);
cal.result();
input.close();
}
private static int verifyAndGetNumber(String line) throws Exception {
if (line.matches("\\d+")) {
return Integer.parseInt(line);
}
throw new Exception("wrong number!");
}
You can count the number of Integer inputs entered by the user and that way you can solve the problem.
So you can modify the code as:
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Calculate cal = new Calculate();
Scanner input = new Scanner(System.in);
int number1 = 0;
int number2 = 0;
boolean isNumber;
int totalEnteredNumbers=0;
int currNumber=1;
do {
System.out.println("enter number"+currNumber+" please : ");
if (totalEnteredNumbers==0 && input.hasNextInt()) {
number1 = input.nextInt();
isNumber = true;
currNumber++;
System.out.println("enter number"+currNumber+" please : ");
totalEnteredNumbers++;
}
if (totalEnteredNumbers==1 && input.hasNextInt()) {
number2 = input.nextInt();
isNumber = true;
} else {
System.out.println("wrong number!");
isNumber = false;
input.next();
}
} while (!(isNumber));
cal.setNumbers(number1, number2);
cal.result();
input.close();
}
}
Anyways here you can also remove the boolean variable isNumber from termination condition by replacing it with while(totalEnteredNumbers<2);.
However this can also be solved with the following code:
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Calculate cal = new Calculate();
Scanner input = new Scanner(System.in);
int number1 = 0;
int number2 = 0;
boolean numberTaken=false;
while(!numberTaken)
{
System.out.print("Enter number1 : ");
String ip=input.next();
try
{
number1=Integer.parseInt(ip); //If it is not valid number, It will throw an Exception
numberTaken=true;
}
catch(Exception e)
{
System.out.println("Wrong Number!");
}
}
numberTaken=false; //For second input
while(!numberTaken)
{
System.out.print("Enter number2 : ");
String ip=input.next();
try
{
number2=Integer.parseInt(ip); //If it is not valid number, It will throw an Exception
numberTaken=true;
}
catch(Exception e)
{
System.out.println("Wrong Number!");
}
}
cal.setNumbers(number1, number2);
cal.result();
input.close();
}
}
Related
So basically I am trying to figure out how to stop this program using Integer.valueOf(String s) or Integer.parseInt(String s) by typing "end" for the user input
import java.util.Scanner;
public class monkey1{
public static void main(String[] args){
Scanner s = new Scanner(System.in);
int sum = 0;
int lol = 1;
do {
System.out.print("Enter a number: ");
lol = s.nextInt();
sum += lol;
if (lol > 0) {
System.out.println("Sum is now: " + sum);
}
} while (lol>0);
}
}
First - you need to change lol=sc.nextInt() to String tmp = s.nextLine()
Second - do
try {
if (tmp.equals("END")) {
break; // This will exit do-while loop
}
lol = Integer.parseInt(tmp);
} catch (NumberFormatException e) {
e.printStackTrace();
// Here you can also exit loop by adding break. Or just ask user to enter new text.
}
you should learn how to use try/catch.
Here we go:
String text = "";
int lol = 1;
do {
System.out.print("Enter a number: ");
text = s.nextLine();
try {
lol = Integer.valueOf(text);
}catch (Exception e){
System.out.println("Exit");
System.exit(0);
}
Here is your code
package Phone;
import java.util.Scanner;
public class monkey1{
public static void main(String[] args){
Scanner s = new Scanner(System.in);
int sum = 0;
int hi = 1;
do {
System.out.print("Enter a number: ");
String lol = s.nextLine();
if(lol.equals("end")) {
break;
}
hi = Integer.parseInt(lol);
sum += hi;
if (hi > 0) {
System.out.println("Sum is now: " + sum);
}
} while (hi > 0);
}
What I did here is I changed lol to hi for adding and took String input so that you can input end...
I would suggest checking if s.equals("end") before converting to int so something like this:
do {
System.out.print("Enter a number: ");
String userValue = s.nextLine();
if(userValue.equals("end")
break;
lol = Integer.parseInt(userValue);
sum += lol;
if (lol > 0){
System.out.println("Sum is now: " + sum);
}
}while (lol>0);
so I am trying to do my homework, this being the question:
Write a program that prompts the user to read two integers and displays their sum. If anything but an integer is passed as input, your program should catch the InputMismatchException that is thrown and prompt the user to input another number by printing "Please enter an integer."
Below is the sample run and what I am supposed to test.
SAMPLE RUN #1: java InputMismatch
Enter an integer: 2.5↵
Please enter an integer↵
Enter an integer: 4.6↵
Please enter an integer↵
Enter an integer: hello!↵
Please enter an integer↵
Enter an integer:7↵
Enter an integer:5.6↵
Please enter an integer↵
Enter an integer:9.4↵
Please enter an integer ↵
Enter an integer:10↵
17↵
When I am testing my code and putting in the integers, it works as it is supposed to, however, I am stuck on getting the integers to add together when both inputs are entered correctly. What am I doing wrong?
import java.util.InputMismatchException;
import java.util.Scanner;
public class TestInputMismatch {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int num1 = 0;
int num2 = 0;
boolean isValid = false;
while (!isValid) {
try {
System.out.print("Enter an integer: ");
int number = input.nextInt();
System.out.println("The number entered is " + number);
boolean continueInput = false;
}
catch (InputMismatchException ex) {
System.out.println("Try again. (" + "Incorrect input: an integer is required)");
input.nextLine();
}
}
System.out.println((num1 + num2));
}
}
try adding another condition to your while and putting the numbers in an array.
int[] numbers = new int[2];
and change this in your while loop:
int count = 0;
while (!isValid && count <2) {
try {
System.out.print("Enter an integer: ");
numbers[count] = input.nextInt();
count++;
System.out.println("The number entered is " + number);
boolean continueInput = false;
}
catch (InputMismatchException ex) {
System.out.println("Try again. (" + "Incorrect input: an integer is required)");
input.nextLine();
}
}
Hope that helped.
Check with this approach:
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int[] numArray = new int[2];
int count = 0;
while (count <= 1) {
try {
System.out.print("Enter an integer: ");
int number = input.nextInt();
System.out.println("The number entered is " + number);
numArray[count] = number;
count++;
} catch (InputMismatchException ex) {
System.out.println("Try again. (" + "Incorrect input: an integer is required)");
input.nextLine();
}
}
int num1 = numArray[0];
int num2 = numArray[1];
System.out.println((num1 + num2));
}
You need to stitch together the logic. As you are taking 2 numbers 2 flags will ensure you got correct input for both variables. Also both flags ensure you are taking input correctly for num1 or num2 when an exception occurs.
If you need to input n arbitrary integers, then you may want to use dynamic collections and add numbers to collection.
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int num1 = 0;
int num2 = 0;
boolean num1Valid = false;
boolean num2Valid = false;
while (num1Valid==false || num2Valid==false) {
try {
if(num1Valid == false) {
System.out.print("Enter an integer for num1: ");
num1 = input.nextInt();
System.out.println("The number entered for num1 is " + num1);
num1Valid = true;
}
if(num2Valid == false) {
System.out.print("Enter an integer for num2: ");
num2 = input.nextInt();
System.out.println("The number entered for num2 is " + num2);
num2Valid = true;
}
}
catch (InputMismatchException ex) {
System.out.println("Try again. (" + "Incorrect input: an integer is required)");
input.nextLine();
}
}
input.close()
System.out.println((num1 + num2));
}
You need capture the exception, in this case you can using e.getMessage()
public class TestInputMismatch {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int num1=0, number=0;
boolean isValid = false;
while (!isValid) {
try {
System.out.print("Enter an integer: ");
number = input.nextInt();
if(number > 0) {
System.out.println("The number entered is " + number);
}
num1 += number;
System.out.println("are would you like continue the program? Y or
N ");
String condition = input.next();
if(condition.equalsIgnoreCase("Y")) {
isValid = false;
} else {
isValid = true;
}
}
catch (InputMismatchException ex) {
System.out.println(ex.getMessage());
System.out.println("You cannot type words");
isValid = true;
}
}
System.out.println("Result = " + num1);
input.close();
}
}
in another case do you can use the method matches using expression language
saw example below:
if(valor.matches("[0-9]*"))
You can add the two numbers inside the try block
import java.util.InputMismatchException;
import java.util.Scanner;
public class TestInputMismatch {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int num1 = 0;
int num2 = 0;
boolean isValid = false;
while (!isValid) {
try {
System.out.print("Enter an integer: ");
num1 = input.nextInt();
System.out.print("Enter an integer: ");
num2 = input.nextInt();
System.out.println("The numbers you entered are " + num1 + ","+num2);
int sum = num1+num2;
System.out.println("The sum Of the numbers you entered is: "+ sum);
boolean continueInput = false;
}
catch (InputMismatchException ex) {
System.out.println("Try again. (" + "Incorrect input: an integer is required)");
input.nextLine();
}
}
System.out.println((num1 + num2));
}
}
import java.util.Scanner;
import java.util.InputMismatchException;
public class InputMismatch {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int[] numArray = new int[2];
int count = 0;
while (count <= 1) {
try {
System.out.print("Enter an integer:");
int number = input.nextInt();
numArray[count] = number;
count++;
} catch (InputMismatchException e) {
System.out.println("Please enter an integer.");
input.nextLine();
}
}
System.out.println(numArray[0] + numArray[1]);
}
}
I am writing a program to take the input for a sequence
import java.util.Scanner;
public class FibonacciCode {
public static void main(String[] args) {
System.out.println("Enter a number");
int count, number0 = 0, number1 = 1, loop = 0;
Scanner userInput = new Scanner(System.in);
count = userInput.nextInt();
while(loop > count)
{
System.out.print(number0 + ", ");
int sum = number0 + number1;
number0 = number1;
number1 = sum;
loop++;
}
}
}
This should be a usable implementation:
public class Menu {
public static void main(String[] args) {
Scanner a = new Scanner(System.in);
boolean orderCompleted = false;
while(!orderCompleted) {
printMenu();
String orderString = a.nextLine();
int order = Integer.parseInt(orderString);
int total = 0;
if(order == 1) {
} else if(order == 2) {
} else if(order == 3) {
} else if(order == 4) {
} else if(order == 5) {
}
System.out.println("Would you like to order more? Press 'y' to continue or 'n' to finish order.");
orderString = a.nextLine();
if(orderString.equals("n")){
orderCompleted = true;
}
}
}
private static void printMenu() {
System.out.println("Welcome to Hess Burgers");
System.out.println("1- Cheeseburger.............$7");
System.out.println("2- Barbeque Burger..........$8");
System.out.println("3- Southwestern Burger......$9");
System.out.println("4- Bacon Cheeseburger.......$10");
System.out.println("5- Double Stack Burger......$11");
System.out.println("");
System.out.print("Please enter your order selection:");
}
}
I pulled the menu printing to a separate method, and re-used scanner a as well as re-using the orderString. The while loop checks a completedOrder boolean flag, so that it can be used to do completion tasks prior to exiting the order loop if need be.
import java.util.Scanner;
public class FibonacciCode {
public static void main(String[] args) {
System.out.println("Enter a number");
int count, number0 = 0, number1 = 1, loop = 0;
Scanner userInput = new Scanner(System.in);
count = userInput.nextInt();
while(loop > count)
{
System.out.print(number0 + ", ");
int sum = number0 + number1;
number0 = number1;
number1 = sum;
loop++;
}
}
}
A while loop does whatever is in the block as long as the condition is true, in your case, you are simply repeating order = b.nextInt() until something other than 'y' is given as input
while (continuePlay= b.nextLine().equalsIgnoreCase ("y")) {
order = b.nextInt(); // This is inside the block
}
you should use a do while loop instead, like so:
do{
System.out.println("Welcome to Hess Burgers");
System.out.println("1- Cheeseburger.............$7");
System.out.println("2- Barbeque Burger..........$8");
System.out.println("3- Southwestern Burger......$9");
System.out.println("4- Bacon Cheeseburger.......$10");
System.out.println("5- Double Stack Burger......$11");
System.out.println(" ");
System.out.print("Please enter your order selection:");
Scanner a = new Scanner(System.in);
int order = a.nextInt();
int total = 0;
boolean continuePlay = true;
if (order == 1 ) {
} else if (order == 2) {
} else if (order == 3) {
} else if (order == 4) {
} else if (order == 5) {
}
Scanner b = new Scanner(System.in);
System.out.println("Would you like to order more? Press 'y' to continue or 'n' to finish order.");
} while (continuePlay= b.nextLine().equalsIgnoreCase ("y"));
Also I'd recommend reading some basic programming books or tutorials instead of going directly to Stack Overflow.
When I use for loop for subtraction, i don't get a correct output.
What logic should i apply in my code to get my subtraction correctly using for loop?
Please help me as i am new in JAVA.
My code is as Follow:
import java.io.*;
import java.util.*;
class Sub
{
public static void main(String args[])
{
Scanner s=new Scanner(System.in);
int a,n,i;
String yn;
boolean loop=true;
while(loop)
{
try
{
do
{
loop=true;
System.out.println("Enter how many numbers to Subtract?: ");
n=s.nextInt();
int sum=0;
for(i=1;i<=n;)
{
try
{
System.out.println("Enter number "+i+" : ");
a=s.nextInt();
sum=a-sum;
i++;
}
catch(Exception e)
{
System.out.println("Invalid Entry. Try again!!");
}
}
System.out.println("Answer is:"+sum);
System.out.println("Do you want to continue?(Y/N): ");
yn=s.next();
loop=yn.equals("Y")||yn.equals("y");
}while(loop);
}
catch(Exception e)
{
System.out.println("Re-enter the Limit");
}
}
}
}
You should start with sum as the first number (not zero) and subtract the rest of the numbers from it:
loop=true;
System.out.println("Enter how many numbers to Subtract?");
n=s.nextInt();
int sum=0;
for(i=1;i<=n;)
{
try
{
System.out.println("Enter number "+i+" : ");
a=s.nextInt();
sum=a-sum;
i++;
}
catch(Exception e)
{
System.out.println("Invalid Entry. Try again!!");
}
}
to:
...
loop = true;
System.out.println("Enter how many numbers to Subtract?: ");
n = s.nextInt();
System.out.println("Enter number 1 : ");
int sum = s.nextInt();
for (int i=2; i <= n; i++) {
try {
System.out.println("Enter number " + i + " : ");
a = s.nextInt();
sum -= a;
} catch (Exception e) {
System.out.println("Invalid Entry. Try again!!");
}
}
...
Further, instead of doing:
yn.equals("Y") || yn.equals("y")
you can use equalsIgnoreCase():
yn.equalsIgnoreCase("Y")
And last, you should use meaningful names for variables (it's recommended to develop good habits even if it's such a small program), so instead of:
int a, n, i; // you can define and use i inside the for-loop - no need to define it outside
String yn;
consider using more expressive names, such as:
int inputNumber, numberOfVariables;
String continueLooping;
The following version could be improved (refactored even further):
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while (true) {
int numOfArguments = getNumberOfArguments(scanner);
int sum = getNextNumberFromUser(scanner, 1);
for (int i = 2; i <= numOfArguments; i++) {
sum -= getNextNumberFromUser(scanner, i);
}
System.out.println("Answer is: " + sum + "\n\nDo you want to continue?(Y/N): ");
String runAgain = scanner.next();
if (runAgain.equalsIgnoreCase("N")) {
break;
}
}
}
private static int getNextNumberFromUser(Scanner scanner, int i) {
while (true) {
try {
System.out.println("Enter number " + i + " : ");
return scanner.nextInt();
} catch (InputMismatchException e) {
System.out.println("Invalid Entry. Try again!!");
scanner.nextLine();
}
}
}
private static int getNumberOfArguments(Scanner scanner) {
int numberOfArguments = -1;
System.out.println("Enter how many numbers to Subtract?: ");
while (numberOfArguments == -1) {
try {
numberOfArguments = scanner.nextInt();
if (numberOfArguments <= 0) {
numberOfArguments = -1;
}
} catch (InputMismatchException e) {
System.out.println("Illegal number of arguments to subtract, please try again: ");
scanner.nextLine();
}
}
return numberOfArguments;
}
I am an absolute beginner, no experience in any programming language.
I wrote a program as an exercise for converting Arabic numbers to Roman numbers. It works. However I want to add a part for dealing with problem if a string is entered instead of integer. And don't know how to do this. I tried to use try/catch, but I don't know how to use it correctly. Now the program asks me twice to enter a number. What to do?
Here is he main method:
public static void main(String[] args) {
int numArabic;
boolean validEntry;
try {
System.out.println("Enter an integer number between 1 and 3999!");
Scanner scan = new Scanner(System.in);
numArabic = scan.nextInt();
validEntry = true;
} catch (InputMismatchException e) {
System.out.println("Entered value is not an integer!");
}
System.out.println("Enter an integer number between 1 and 3999!");
Scanner scan = new Scanner(System.in);
numArabic = scan.nextInt();
if ((numArabic < 1) || (numArabic > 3999)) {
System.out.println();
System.out.print("Wrong number. ");
System.out.print("Enter an integer number between 1 and 3999!");
System.out.println();
}
else {
String numRoman1 = toRomanOne(numArabic % 10);
String numRoman2 = toRomanTwo(((numArabic / 10) % 10));
String numRoman3 = toRomanThree(((numArabic / 100) % 10));
String numRoman4 = toRomanFour(numArabic / 1000);
System.out.print("The number " + numArabic + " is equal to: ");
System.out.print(numRoman4+numRoman3+numRoman2+numRoman1 + ".");
}
}
Your control mechanism is true but only works once. You have to put it inside a loop so that it can allow user to enter an integer at last.
boolean validEntry;
do {
try {
System.out.println("Enter an integer number between 1 and 3999!");
Scanner scan = new Scanner(System.in);
numArabic = scan.nextInt();
validEntry = true;
}
catch (InputMismatchException e) {
validEntry = false;
System.out.println("Entered value is not an integer!");
}
}
while(!validEntry);
You can use Scanner#hasNextInt() method to check that.
This method returns true if the next token in this scanner's input can be interpreted as an int value.
if (scan.hasNextInt()) {
// Do the process with Integer.
} else {
// Do the process if it is not an Integer.
}
Note that, this will cover all the Inputs which are not Integer, not only String.
public static void main(String[] args) {
int numArabic;
boolean validEntry = false;
while (validEntry = false){
try {
System.out.println("Enter an integer number between 1 and 3999!");
Scanner scan = new Scanner(System.in);
numArabic = scan.nextInt();
validEntry = true;
}
catch (InputMismatchException e) {
System.out.println("Entered value is not an integer!");
validEntry = false;
}
}
if ((numArabic < 1) || (numArabic > 3999)) {
System.out.println();
System.out.print("Wrong number. ");
System.out.print("Enter an integer number between 1 and 3999!");
System.out.println();
}
else {
String numRoman1 = toRomanOne(numArabic % 10);
String numRoman2 = toRomanTwo(((numArabic / 10) % 10));
String numRoman3 = toRomanThree(((numArabic / 100) % 10));
String numRoman4 = toRomanFour(numArabic / 1000);
System.out.print("The number " + numArabic + " is equal to: ");
System.out.print(numRoman4+numRoman3+numRoman2+numRoman1 + ".");
}
}
Try This :
boolean b=true;
while(b)
{
try
{
System.out.println("Enter an integer number between 1 and 3999!");
Scanner scan = new Scanner(System.in);
numArabic = scan.nextInt();
validEntry = true;
}
catch (InputMismatchException e)
{
System.out.println("Entered value is not an integer!");
}
if(validEntry)
{
if ((numArabic < 1) || (numArabic > 3999))
{
System.out.println();
System.out.print("Wrong number. ");
System.out.print("Enter an integer number between 1 and 3999!");
System.out.println();
}
else
{
String numRoman1 = toRomanOne(numArabic % 10);
String numRoman2 = toRomanTwo(((numArabic / 10) % 10));
String numRoman3 = toRomanThree(((numArabic / 100) % 10));
String numRoman4 = toRomanFour(numArabic / 1000);
System.out.print("The number " + numArabic + " is equal to: ");
System.out.print(numRoman4+numRoman3+numRoman2+numRoman1 + ".");
}
b=false;
}//end of if
}//end of while
Try this,
you need to initialize numArabic to some value first.
public static void main(String[] args) {
int numArabic = 0;
boolean validEntry;
try {
System.out.println("Enter an integer number between 1 and 3999!");
Scanner scan = new Scanner(System.in);
numArabic = scan.nextInt();
validEntry = true;
}
catch (InputMismatchException e) {
System.out.println("Entered value is not an integer!");
}
if ((numArabic < 1) || (numArabic > 3999)) {
} else {
}
}
The Program what you entered is free from syntax errors and logical errors.But for asking only one time to enter the integer value just rewrite the code as following.We are attaching second sop function in catch block.So if the input is mismatch it will ask for again re-enter.
public static void main(String[] args) {
int numArabic;
boolean validEntry;
try {
System.out.println("Enter an integer number between 1 and 3999!");
Scanner scan = new Scanner(System.in);
numArabic = scan.nextInt();
validEntry = true;
} catch (InputMismatchException e) {
System.out.println("Entered value is not an integer!");
System.out.println("Enter an integer number between 1 and 3999!");
Scanner scan = new Scanner(System.in);
numArabic = scan.nextInt();
}