Noob here so bear with me..I was working on a Java program that takes the users input from the JoptionPane, and uses a set of if-else statements to verify the date while considering the leap years. The problem I seem to be having when it runs is that it validates dates that aren't possible. For example, 2/29/2014, it says it's a valid date, but in reality it isn't.
Insight on this issue would be highly appreciated.
import java.util.Arrays;
import javax.swing.JOptionPane;
public class vaildDate {
public static void main(String[] args) {
// TODO Auto-generated method stub
int month, day, year;
String userInput = JOptionPane.showInputDialog("Enter a valid date in mm/dd/yyyy format: ");
String [] date = userInput.split("/");
String mm = date[0];
String dd = date [1];
String yyyy = date [2];
month = Integer.parseInt(mm);
day = Integer.parseInt(dd);
year = Integer.parseInt(yyyy);
System.out.println(mm+dd+yyyy);
boolean validLeapYear;
boolean validDate;
if(month>=1 && month <=12&& day>=1 && day<=31)
{
if(month == 4 || month == 9 || month == 6 || month == 11 && day <= 30)
{
validDate = true;
}
if(( month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 11 || month == 12) && (day <= 31))
{
validDate = true;
}
else{
validDate =false;
}
if((year % 400 == 0 ) || (year % 4 == 0) && (year % 100 != 0))
{
validLeapYear = true;
}
if ((month == 2 && day == 29) && (validLeapYear = false ))
{
validDate = false;
}
if((month == 2 && day <= 29) && (validLeapYear = true ))
{
validDate = true;
}
if(validDate = true)
{
JOptionPane.showMessageDialog(null, month +"/"+day+"/"+year+" is a valid date");
}
else if(validDate = false) {
JOptionPane.showMessageDialog(null,"Your date is invalid");
}
}
}
}
Instead of equating booleans your are assigning the values which return the results of your assignment.
For example:
if (validDate = true)
The above statement would return true. Instead, in all your boolean checks just validate the boolean value as is.
if (validDate)
To remove the compiler errors, you can initialize your 2 boolean vars to false.
You changed code would look something like:
public static void main(String[] args) {
// TODO Auto-generated method stub
int month, day, year;
String userInput = JOptionPane
.showInputDialog("Enter a valid date in mm/dd/yyyy format: ");
String[] date = userInput.split("/");
String mm = date[0];
String dd = date[1];
String yyyy = date[2];
month = Integer.parseInt(mm);
day = Integer.parseInt(dd);
year = Integer.parseInt(yyyy);
System.out.println(mm + dd + yyyy);
boolean validLeapYear = false;
boolean validDate = false;
if (month >= 1 && month <= 12 && day >= 1 && day <= 31) {
if (month == 4 || month == 9 || month == 6 || month == 11
&& day <= 30) {
validDate = true;
}
if ((month == 1 || month == 3 || month == 5 || month == 7
|| month == 8 || month == 11 || month == 12)
&& (day <= 31)) {
validDate = true;
} else {
validDate = false;
}
if ((year % 400 == 0) || (year % 4 == 0) && (year % 100 != 0)) {
validLeapYear = true;
}
if ((month == 2 && day == 29) && (!validLeapYear)) {
validDate = false;
}
if ((month == 2 && day <= 29) && (validLeapYear)) {
validDate = true;
}
if (validDate) {
JOptionPane.showMessageDialog(null, month + "/" + day + "/"
+ year + " is a valid date");
}
else if (!validDate) {
JOptionPane.showMessageDialog(null, "Your date is invalid");
}
}
}
A quick search on Google shows there are easier ways to validate a date. Please see this one:
http://www.mkyong.com/java/how-to-check-if-date-is-valid-in-java/
It uses the date parse and catches the exception if the date is not valid (cannot be parsed).
If you want to stick with your algorithm, I suggest to use an IDE like Eclipse and debug set by step while keeping a look on the value of your variables. You clearly have an algorithm problem, which will become obvious while debugging.
Hope that helps.
Related
I am basically refining, completing and trying to compile my code for an exercise. The objective is to create a calendar.
Unable to figure the problem, have tried to find the inappropriate statements but no solution. I have tried to find other sources in order to gain a solution but I could not figure out the problem.
The error:
MyCalendar.java:60: illegal start of expression
else if(year%4!==0)
^
The code:
public class MyCalender {
int day, month, year;
boolean isDateValid = true;
public MyCalender(int day, int month, int year) {
this.day = day;
this.month = month;
this.year = year;
if (month > 12) //Day and Month validation
{
isDateValid = false;
} else if (month == 1 || month == 3 || month == 5 || month == 7 || month == 9 || month == 12) {
if (day <= 31) {
isDateValid = true;
} else if (day >= 31) {
isDateValid = false;
}
} else if (month == 2 || month == 4 || month == 6 || month == 8 || month = 10 || month == 12) {
if (day <= 30) {
isDateValid = true;
} else if (day >= 30) {
isDateValid = false;
}
} else if (month == 2) //Consideration of February month and leap year validation
{
if (year % 4 == 0) {
if (day <= 29) {
isDateValid = true;
} else if (day >= 29) {
isDateValid = false;
}
} else if (year % 4 != = 0) {
if (day <= 28) {
isDateValid = true;
} else if (day >= 28) {
isDateValid = false;
}
}
}
}
boolean isDateValid() {
if (isDateValid) {
System.out.println("is a Valid Date");
return true;
}
if (!isDateValid) {
System.out.println("is not a Valid Date,please re-input Date");
return false;
}
return isDateValid;
}
public int getDay() {
return day;
}
public int getMonth() {
return month;
}
public int getYear() {
return year;
}
public static void main(String[] args) {
MyCalender d = new MyCalender(29, 02, 2019);
System.out.println("Date" + d.getDay() + "/" + d.getMonth() + "/" + d.getYear());
d.isDateValid();
MyCalender d1 = new MyCalender(25, 02, 2019);
System.out.println("Date" + d1.getDay() + "/" + d1.getMonth() + "/" + d1.getYear());
d1.isDateValid();
}
}
The output is expected to be:
java MyCalendar 29/02/2019
29/02/2019 in not a valid date, please re-input a valid date: 25/05/2019
25/05/2019 is a Saturday and located in the fourth week of May 2019
The calendar of May 2019 is:
SUN MON TUE WED THU FRI SAT
1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31
You have to use != rather than !==.
Adding parentheses helps too.
else if( (year%4) != 0 )
…instead of:
else if(year%4 !== 0)
I'm trying to make it so the user has 3 chances to enter correct input, and after the 3rd try the program should close and I'll give a custom String. If at any point they enter valid data the program should execute. I would like to add error handling to the code:
import java.util.Scanner;
{
public static void main(String[] args){
Scanner in = new Scanner(System.in);
int month, day; String season = null;
System.out.print("Enter Month & Day: ");
month = in.nextInt(); day = in.nextInt();
if(1 <= month && month <= 3){
season = "Winter";
if((month == 3) && (21 <= day))
season = "Spring";
} else if (4 <= month && month <=6){
season = "Spring";
if((month == 6) && (21 <= day))
season = "Summer";
} else if (7 <=month && month <=9){
season = "Summer";
if((month == 9) && (21 <= day))
season = "Fall";
} else if (10 <= month && month <= 12){
season = "Fall";
if((month == 12) && (21 <= day))
season = "Winter";
}
System.out.println(season);
}
}
Something like this might help you. Code is self explanatory.
private static final int RETRY_COUNT = 3
retryCount = 0
boolean invalid = true;
while(invalid && retryCount++ < RETRY_COUNT){
try{
invalid = false;
Scanner sc = new Scanner(System.in)
.
.
.
}catch(Exception e){
invalid = true;
}
}
my code doesn't return any value and i have no idea why. My assignment requires me to write a code that accepts date in mm/dd/yyyy format and im required to put leap year in. The problem is, i dont get back any input. Im an amateur ad i dont know what is wrong. Im also allowed to use Case statment but I'm not sure how to implement case.
import java.util.Scanner;
public class Question1 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in).useDelimiter("/");
System.out.println("Please enter a date in mm/dd/yyyy format: ");
String mm = sc.next();
String dd = sc.next();
String yyyy = sc.next();
int month = Integer.parseInt(mm);
int day = Integer.parseInt(dd);
int year = Integer.parseInt(yyyy);
if (month <= 0 || month>12)
{
System.out.println("invalid month ");
}
if (year%4 != 0 || month == 02 || day >= 29)
{
System.out.println("invalid date");
}
if (month == 4 || month == 6 || month == 9 || month == 11 || day >= 31)
{
System.out.println("Invalid day");
}
if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12 || day >=32 )
{
System.out.println("Invalid day");
}
else
{
System.out.println("Valid date");
}
}
}
The code sets the delimiter to /. Then you enter something like 12/25/2016. The first sc.next() call gets the 12. The second one gets the 25. The third... waits, because it doesn't see another / so it doesn't know you're done. If you typed 12/25/2016/ with your current code, it would at least give output, even if that output isn't correct yet.
you want to use switch case then go through the below code:
import java.util.Scanner;
public class Question1 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in).useDelimiter("/");
System.out.println("Please enter a date in mm/dd/yyyy/ format: ");
String mm = sc.next();
String dd = sc.next();
String yyyy = sc.next();
int month = Integer.parseInt(mm);
int day = Integer.parseInt(dd);
int year = Integer.parseInt(yyyy);
boolean valid = isValidDate(day,month,year);
if (valid == true)
{
System.out.println("Date is Valid");
}
else
{
System.out.println("Date is InValid");
}
}
public static boolean isValidDate(int day, int month ,int year)
{
boolean monthOk = (month >= 1) && (month <= 12);
boolean dayOk = (day >= 1) && (day <= daysInMonth(year, month));
return (monthOk && dayOk);
}
private static int daysInMonth(int year, int month) {
int daysInMonth;
switch (month) {
case 1:
case 3:
case 5:
case 7:
case 8:
case 10: // go through
case 12:
daysInMonth = 31;
break;
case 2:
if (((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0)) {
daysInMonth = 29;
} else {
daysInMonth = 28;
}
break;
default:
// returns 30 even for nonexistant months
daysInMonth = 30;
}
return daysInMonth;
}
}
take input as 12/25/2016/, not this 12/25/2016.
Here is something to get you started:
final String DELIMITER = "/";
Scanner sc = new Scanner(System.in);
System.out.println("Please enter a date in mm/dd/yyyy format:\n ");
String date = sc.next();
sc.close();
String[] dateParts = date.split(DELIMITER);
//check : if dateParts size is not 3 ....something is wrong
String mm = dateParts[0];
String dd = dateParts[1];
String yyyy = dateParts[2];
System.out.println(mm+" "+ dd +" "+ yyyy);
It seems you have put else in wrong place. Suppose you second condition is getting correct and all other false, then also your program will show it as valid date and same on the opposite side.
For example, say day is 30 for any date, then it will satisfy second condition and it will show you "Invalid date".
You should write if else as follows.
If{
If{
If{
}
}
}else{
}
All if must be in a nested if and then else. Your if else sequence is wrong.
I'm supposed to make code that shows the next day, and this works except for the months that end in 31. For example, when I enter 3/31/2000, it gives me 4/2/2000 and skips the first day? I'm not sure why?
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package lab53;
import java.util.Scanner;
/**
*
* #author Owner
*/
public class Lab53 {
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
Scanner keyboardInput = new Scanner(System.in);
int year, month, day;
System.out.println("Enter year/month/day");
year = keyboardInput.nextInt();
month = keyboardInput.nextInt();
day = keyboardInput.nextInt();
if ((month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12))
{
day=thirtyOneDaysMonth(day);
if(day==1 && month==12){
++year;
month=1;
}
else if(day==1 && month!=12)
++month;
}
if ((month==2 || month == 4 || month == 6 || month == 9 || month == 11))
{
day=thirtyDaysMonth(day);
if(month==2 && isLeapYear(year))
{
if(day>29)
{
++month;
day=1;
}
}
else if( day>28 && month==2)
{
++month;
day=1;
}
else
{
if(day==1)
{
++month;
day=1;
}
}
}
System.out.println("The next date is:"+ month + "/" + day + "/" + year);
}
public static int thirtyOneDaysMonth(int day)
{
if(day==31)
day=1;
else
++day;
return day;
}
public static int thirtyDaysMonth(int day)
{
if(day==30)
day=1;
else
++day;
return day;
}
public static boolean isLeapYear(int year)
{
if((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0)))
return true;
else
return false;
}
}
Change if ((month==2 || month == 4 || month == 6 || month == 9 || month == 11)) to else if ((month==2 || month == 4 || month == 6 || month == 9 || month == 11)).
On a day = 31 you're updating the month in your if statement. Then you leave the if but then enter your next if statement that handles months with 30 days. Your code then increments the day again.
Because after the first if has increased 3/31/2000 to 4/1/2000 the second if is evaluated which will again increase the day. Make the second if an else if instead.
In the case of month==3 and day==31, day is bumped back to 1 by
day=thirtyOneDaysMonth(day);
then the month is bumped up by
else if(day==1 && month!=12)
++month;
then the next if statement is true because now month == 4
if ((month==2 || month == 4 || month == 6 || month == 9 || month == 11))
connecting it to the previous if statement with an else if will fix the issue
else if ((month==2 || month == 4 || month == 6 || month == 9 || month == 11))
I am trying to write a method that takes a single int parameter that is the numeric month and returns the number of days in the given month. So, a parameter of 1 would return 31 since there are 31 days in January and a parameter of 2 would return 28 since there are 28 days in February.
Here's what I have so far:
public static void daysInMonth(int month) {
if (month == 1||3||5||7||8||10||12)
System.out.println("31");
else if (month == 4||6||9||11)
System.out.println("30");
else if (month == 2)
System.out.println("28");
I keep getting the error message "operator || cannot be applied to boolean,int." Can anyone help me figure out what to do?
You want something like this:
if ( (month == 1) || (month == 3) || (month == 5) || (month == 7)
|| (month == 8) || (month == 10)
You can avoid any switch or if/else statements with the new Java 1.8 time API using java.time.Month:
public static int daysInMonth(int month) {
return Month.of(month).minLength();
}
You can use the || operator on a boolean expression :
if (month == 1 || month == 3 || month == 5) {
// do something ...
}
|| will result into boolean and then boolean || int is not valid action
what you need is
month == 1 || month == 3 || ...
or a Map<Integer, Integer> monthNumberToMaxDaysMap
also this way you don't have leap year scenario covered, it is suitable to re-use already solved problem
public static void daysInMonth(int month) {
Calendar cal = Calendar.getInstance();
cal.set(Calendar.MONTH, month -1);
return cal.getActualMaximum(Calendar.DAY_OF_MONTH)
}
above method only considers current year, you could leverage it to pass year as well