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Why doesn't my date validation code work?

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.

No output is coming out after I input two values

I can't seem to get the season to appear when I input a month and a day via the Scanner entity. I have tried many diferent methods, though none of them seem to be working. The code is shown below.
public class Lab7Smalls {
public static void main(String[] args){
Scanner scan = new Scanner(System.in);
private int month = 0;
private int day = 0;
String season = "";
String winter = "winter";
String spring = "spring";
String summer = "summer";
String fall = "fall";
System.out.print("Enter a month: ");
month = scan.nextInt();
System.out.print("Enter a day: ");
day = scan.nextInt();
if (month < 0 || month > 12) System.out.println("Not correct");
if(month <= 3){
season = winter;
}
else if(month <= 6){
season = spring;
}
else if(month <= 9){
season = summer;
}
else if(month <= 12){
season = fall;
}
if(month % 3 == 0 && day >= 21){
if(season.equals(winter)){
season = spring;
}
else if(season.equals(spring)){
season = summer;
}
else if(season.equals(summer)){
season = fall;
}
else if(season.equals(winter)){
season = winter;
}
System.out.println("Season: " + season);
}
}
}
The example for the output:
Enter a month: 1
Enter a day: 28

Sorry but this was a little long for a comment,
The System.out.println command is inside if(month % 3 == 0 && day >= 21){....} block, you have entered 1 for the month and as 1%3=1 so of course that if block will not executed and you will see nothing in output, you'll see something if and only if your input data meets the condition of if statement

If the month % 3 != 0 and the day < 21, nothing happens, because there is no else statement. Your code will only print the season if the month % 3 == 0 and the day >=21. You have two options:
The easier option: Move println outside of the if statement.
public static void main(String[] args){
Scanner scan = new Scanner(System.in);
int month;
int day;
String season = "";
System.out.print("Enter a month: ");
month = scan.nextInt();
System.out.print("Enter a day: ");
day = scan.nextInt();
String winter = "winter";
String spring = "spring";
String summer = "summer";
String fall = "fall";
if(month <= 3){
season = winter;
}
else if(month <= 6){
season = spring;
}
else if(month <= 9){
season = summer;
}
else if(month <= 12){
season = fall;
}
if(month % 3 == 0 && day >= 21){
if(season.equals(winter)){
season = spring;
}
else if(season.equals(spring)){
season = summer;
}
else if(season.equals(summer)){
season = fall;
}
else if(season.equals(winter)){
season = winter;
}
}
System.out.println("Season: " + season);
}
Option two: Add an else statement. Don't know why you would want to do this, but I'll put it here anyways.
public static void main(String[] args){
Scanner scan = new Scanner(System.in);
int month;
int day;
String season = "";
System.out.print("Enter a month: ");
month = scan.nextInt();
System.out.print("Enter a day: ");
day = scan.nextInt();
String winter = "winter";
String spring = "spring";
String summer = "summer";
String fall = "fall";
if(month <= 3){
season = winter;
}
else if(month <= 6){
season = spring;
}
else if(month <= 9){
season = summer;
}
else if(month <= 12){
season = fall;
}
if(month % 3 == 0 && day >= 21){
if(season.equals(winter)){
season = spring;
}
else if(season.equals(spring)){
season = summer;
}
else if(season.equals(summer)){
season = fall;
}
else if(season.equals(winter)){
season = winter;
}
System.out.println("Season: " + season);
}else{
System.out.println("Season: " + season);
}
}

"error: variable might not have been initiailzed" [duplicate]

This question already has answers here:
Variables might not have been initialized
(3 answers)
Closed 8 years ago.
Doing some Java practice at home and I keep getting an error with this code.
I want to make a program which tells the season of a month that has been entered (in numerical form) but if the number is greater than 12, it should tell us that the month entered is invalid.
import java.util.Scanner;
class SeasonInput {
public static void main (String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter a month (in numbered form)");
String monthentered = input.nextLine();
int month = Integer.valueOf(monthentered);
String season;
if(month <13) {
if(month == 12 || month == 1 || month == 2)
season = "Winter";
else if(month == 3 || month == 4 || month == 5)
season = "Spring";
else if(month == 6 || month == 7 || month == 8)
season = "Summer";
else if(month == 9 || month == 10 || month == 11)
season = "Autumn";
System.out.println("The season that occurs during that month is " + season);
}
else
System.out.println("Enter a valid month");
}
}

It's a valid error, in your last else you don't set String season.
String season = null; // <-- give it a null. the error will go away.

You have cases where you don't initialize season.
This is what the compiler is complaining about.

Java Valid Dates and JOptionPane

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.

Calculate current Age ; using Java

I am trying to calculate the current age of a user .. but using the format i would like to use has caused some issues for me .
I could just ask separately for the year , month and day but much rather prefer (mm/dd/yyyy)
//Need help turning (mm/dd/yyyy) that the user inputs into:
//yyyy;
//mm;
// dd;
package org.joda.time;
import java.util.Calendar;
import java.util.GregorianCalendar;//needed for leap year
import java.util.Scanner;
import java.io.*;
public class AgeCalculation{
public static void main(String[] args) throws IOException{
int day = 1, month = 0, year = 1, ageYears, ageMonths, ageDays;
Scanner myScanner = new Scanner(System.in);
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
Calendar cd = Calendar.getInstance();
try{
System.out.print("Enter your Date of Birth.(mm/dd/yyyy): ");
Dob = myScanner.nextLine() ;
// how to get year , month and date from (mm/dd/yyyy) format?
year = ;
if(year > cd.get(Calendar.YEAR)){
System.out.print("Invalid date of birth.");
System.exit(0);
}
month =
if(month < 1 || month > 12){
System.out.print("Please enter monthe between 1 to 12.");
System.exit(0);
}
else{
month--;
if(year == cd.get(Calendar.YEAR)){
if(month > cd.get(Calendar.MONTH)){
System.out.print("Invalid month!");
System.exit(0);
}
}
}
if(month == 0 || month == 2 || month == 4 || month == 6 || month == 7 ||
month == 9 || month == 11){
if(day > 31 || day < 1){
//leap year data below
System.out.print("Please enter day between 1 to 31.");
System.exit(0);
}
}
else if(month == 3 || month == 5 || month == 8 || month == 10){
if(day > 30 || day < 1){
System.out.print("Please enter day between 1 to 30.");
System.exit(0);
}
}
else{
if(new GregorianCalendar().isLeapYear(year)){
if(day < 1 || day > 29){
System.out.print("Please enter day between 1 to 29.");
System.exit(0);
}
}
else if(day < 1 || day > 28){
System.out.print("Please enter day between 1 to 28.");
System.exit(0);
}
}
if(year == cd.get(Calendar.YEAR)){
if(month == cd.get(Calendar.MONTH)){
if(day > cd.get(Calendar.DAY_OF_MONTH)){
System.out.print("Invalid date!");
System.exit(0);
}
}
}
}
catch(NumberFormatException ne){
System.out.print(ne.getMessage() + " is not a legal entry!");
System.out.print("Please enter number.");
System.exit(0);
}
Calendar bd = new GregorianCalendar(year, month, day);
ageYears = cd.get(Calendar.YEAR) - bd.get(Calendar.YEAR);
if(cd.before(new GregorianCalendar(cd.get(Calendar.YEAR), month, day))){
ageYears--;
ageMonths = (12 - (bd.get(Calendar.MONTH) + 1)) + (bd.get(Calendar.MONTH));
if(day > cd.get(Calendar.DAY_OF_MONTH)){
ageDays = day - cd.get(Calendar.DAY_OF_MONTH);
}
else if(day < cd.get(Calendar.DAY_OF_MONTH)){
ageDays = cd.get(Calendar.DAY_OF_MONTH) - day;
}
else{
ageDays = 0;
}
}
else if(cd.after(new GregorianCalendar(cd.get(Calendar.YEAR), month, day))){
ageMonths = (cd.get(Calendar.MONTH) - (bd.get(Calendar.MONTH)));
if(day > cd.get(Calendar.DAY_OF_MONTH))
ageDays = day - cd.get(Calendar.DAY_OF_MONTH) - day;
else if(day < cd.get(Calendar.DAY_OF_MONTH)){
ageDays = cd.get(Calendar.DAY_OF_MONTH) - day;
}
else
ageDays = 0;
}
else{
ageYears = cd.get(Calendar.YEAR) - bd.get(Calendar.YEAR);
ageMonths = 0;
ageDays = 0;
}
System.out.print("Age of the person : " + ageYears + " year, " + ageMonths +
" months and " + ageDays + " days.");
}
}

Here's a hint as how you could read in and parse the entered date:
SimpleDateFormat f = new SimpleDateFormat("MM/dd/yyyy"); //note that mm is minutes, so you need MM here
Scanner s = new Scanner( System.in );
String dateLine = s.nextLine();
try
{
Date d = f.parse( dateLine );
System.out.println(d);
}
catch( ParseException e )
{
System.out.println("please enter a valid date in format mm/dd/yyyy");
}
That's just an example and should get you started with reading the date correctly.
For getting the years, days and months in between two dates I'd still recommend using JodaTime since that makes life much easier.
Using standard Java facilities, this could help you:
Calendar c = Calendar.getInstance();
c.setTimeInMillis( System.currentTimeMillis() - d.getTime() );
System.out.println( c.get( Calendar.YEAR ) - 1970 ); //since year is based on 1970, subtract that
System.out.println( c.get( Calendar.MONTH ) );
System.out.println( c.get( Calendar.DAY_OF_MONTH ) );
Note that you need to subtract the smaller date from the bigger, i.e. the difference must be positive (which should be true when subtracting birth dates from the current time).
This would give a difference of 0 years, 9 full months and 26 days between Jan 1st 2011 and Oct 26th 2011, and a difference of 21 years and 1 day (since we already started this day) between Oct 26th 1990 and Oct 26th 2011.

If you want to use JodaTime:
String dob = myScanner.nextLine();
DateTimeFormatter format = DateTimeFormatter.forPattern("MM/dd/yyyy");
DateTime dateTimeOfBirth = DateTime.parse(dob, format);
year = dateTimeOfBirth.getYear();
// Etc

try this, it out puts the age into a form field called age in a form called "form", assumes you called your textbox(where DOB is entered) "dob"
var d =document.getElementById('dob').value.split('/');
var today = new Date();
var bday = new Date(d[2],d[1],d[0]);
var age = today.getFullYear() - bday.getFullYear();
if(today.getMonth() < bday.getMonth() || (today.getMonth() == bday.getMonth() && today.getDate() < bday.getDate()))
{
t = age--;
}
else {
t = age
}
form.age.value = t;
}

You'll pobably need something like that:
SimpleDateFormat sdf = new SimpleDateFormat("dd/mm/yyyy", Locale.US);
Date date = sdf.parse(timestamp);
Calendar cd = Calendar.getInstance();
cd.setTime(date);