We Keep Coding

How do i get my new value to go back through the if statements

I'm trying to get the amount of days until the meeting to go back and print out the day the new meeting is on but I keep getting an integer instead of the string.
import java.util.Scanner;
public class NextMeeting {
public static void main(String [] args) {
int day, daysToMeeting = 0;
Scanner scan = new Scanner(System.in);
System.out.println("Enter the day of the week 0-6: ");
day = scan.nextInt();
System.out.println("Enter the days to meeting: ");
daysToMeeting = scan.nextInt();
if (day == 0) {
System.out.println("Today is Sunday");
} else if (day == 1) {
System.out.println("Today is Monday");
}
else if (day == 2) {
System.out.println("Today is Tuesday");
}
else if (day == 3) {
System.out.println("Today is Wednesday");
}
else if (day == 4) {
System.out.println("Today is Thursday");
}
else if (day == 5) {
System.out.println("Today is Friday");
}
else if (day == 6) {
System.out.println("Today is Saturday");
}
System.out.println("Today is: " + day);
if( daysToMeeting >= 6) {
day = daysToMeeting - 7;
}
else {
day = day + 6;
}
System.out.println("Days to the meeting is " + daysToMeeting + " +days.");
System.out.println("Meeting day is : " + Integer.toString(day));
}
}
The output for days is still 3 but we need to get it to print out Wednesday. I don't know how to make that happen.

You can use DayOfWeek enum.
System.out.println("Meeting day is : " + DayOfWeek.of(day).toString());
You can also remove nested if-else statement and use DayOfWeek enum to display "Today is xyz-day".

You are printing out integers because day is an int. It may be inefficient but an easy fix is to create a String variable and in another if-statement block below the daysToMeeting if-else block, assign the String to each corresponding integer, such as
String meetingDay;
if(day == 1){
meetingDay = "Monday";
}
and then print out using the String variable.
System.out.println("Meeting day is : " + meetingDay);

Just create a method which will return the day of week String by passing the day int. Then print the result.
public String intToDayName(int day) {
if(day > 6) {
day = day % 7;
}
if (day == 0) {
return "Sunday";
} else if (day == 1) {
return "Monday";
}
else if (day == 2) {
return "Tuesday";
}
else if (day == 3) {
return "Wednesday";
}
else if (day == 4) {
return "Thursday";
}
else if (day == 5) {
return "Friday";
}
else if (day == 6) {
return "Saturday";
}
return "Error";
}
calling it in your prints:
System.out.println("Meeting day is : " + intToDayName(daysToMeeting));
System.out.println("Today is " + intToDayName(day));
If you actually want your code to go back and print the first if-else statements then I suggest looping.

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.

Validating date from user input

I'm writing a program where I am supposed to have the user input a date from the year 0 - 4000. I'm supposed to see if the date is valid, and if it was a leap year or not. I'm having problems in my code.
I'm getting an else without error on line 57.
I also am not sure how to how to say if the date is valid or not.
IE: this date is valid, is a leap year - or is not valid is not a leap year ...etc...
I'm still a beginner so I dont want the code written for me but I would like to know how to fix it! Thank you.
import java.util.*;
public class LegalDate //file name
{
public static void main (String [] args)
{
Scanner kb = new Scanner (System.in); //new scanner
//name the variables
int month, day, year;
int daysinMonth;
boolean month1, year1, day1;
boolean validDate;
boolean leapYear;
//ask the user for input
//I asked the MM/DD/YYYY in seperate lines to help me visually with the program
System.out.println("Please enter the month, day, and year in interger form: " );
kb.nextInt();
//now I'm checking to see if the month and years are valid
if (month <1 || month >12)
{ month1 = true;}
if (year <0 || year >4000)
{year1= true;}
//I'm using a switch here instead of an if-else statement, which can also be used
switch (month) {
case 1:
case 3:
case 5: //months with 31 days
case 7:
case 8:
case 10:
case 12:
numDays = 31;
break;
case 4:
case 6: //months with 30 days
case 9:
case 11:
numDays = 30;
break;
case 2:
if (((year % 4 == 0) && !(year % 100 == 0)) || (year % 400 == 0)) //formula for leapyear
numDays = 29;
{
system.out.println("is a leap year");
}
else
numDays = 28;
{
system.out.println("is not a leap year");
}
break;
default:
System.out.println("Invalid month.");
break;
if (month1 == true)
if (day1 == true)
if (year1 == true)
System.out.println ("date is valid ");
else
if (month1 == false)
System.out.println ("date is invalid");
else
if (day1 == false)
System.out.println ("date is invalid");
else
if (year1 == false)
System.out.println ("date is invalid");
}}
}

On line 57, you open a new code block but nothing is able to access it. I believe you meant to type:
else{
numDays = 28;
system.out.println("is not a leap year");
}
As a small tip, you can change this:
if (month1 == true)
if (day1 == true)
if (year1 == true)
System.out.println ("date is valid ");
to this:
if (month1 && day1 && year1)
System.out.println ("date is valid ");
Since the boolean comparison operators return true or false, you can tell that the condition just needs to be boolean. Since month1, day1, and year1 are all boolean values, you dont need to compare them to anything.
What the condition means, in the event you don't know, is if month1 and day1 and year1 are all true, then print date is valid

Why don't you try Java 8 date time API
It validates date and do much more for you
Like
try {
LocalDate date =LocalDate.of(2016, 12, 31);
if(date.isLeapYear())
System.out.println("Leap year");
else
System.out.println("Not leap year");
}
catch(DateTimeException e) {
System.out.println(e.getMessage());
}

You don't appear to be placing the code between your 'if' and 'else' statements in curly brackets, which means that the statement will only apply to the next line. For example:
if (a)
b = true
c = true
else
d = true
is read as
if (a) {
b = true
}
c = true
else {
d = true
}
Hopefully, you can see how the compiler wouldn't understand this, as an 'else' statement must occur directly after its associated 'if' block.
I would suggest adding some methods to simplify your code. For example:
public static boolean isLeapYear(int year) {
return (((year % 4 == 0) && !(year % 100 == 0)) || (year % 400 == 0));
}
Also, if you use boolean variables to store information, you can print it all neatly at the end. For example, you could instantiate a variable 'isValid' to true at the top of your code, set it to false if you calculate that the date is invalid, and use an if statement at the end to print your result.
I know you said you didn't want it written for you, but that's the easiest way to demonstrate the importance of methods. Hopefully you can see how this is more readable than your version?
import java.util.Scanner;
public class LegalDate {
static final int maxYear = 4000;
public static void main (String [] args) {
int month, day, year;
boolean leapYear, validDate = false;
Scanner kb = new Scanner (System.in);
System.out.println("Please enter the month, day, and year in interger form.");
System.out.print("Month: ");
month = kb.nextInt();
System.out.print("Day: ");
day = kb.nextInt();
System.out.print("Year: ");
year = kb.nextInt();
leapYear = isLeapYear(year);
validDate = isValidDate(month, day, year);
System.out.printf("%nThe date is %svalid and is %sa leap year.%n", validDate ? "" : "not ", leapYear ? "" : "not ");
kb.close();
}
public static int numDaysInMonth(int month, boolean isLeapYear) {
switch (month) {
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
return 31;
case 4:
case 6:
case 9:
case 11:
return 30;
case 2:
if (isLeapYear) {
return 29;
} else {
return 28;
}
default:
return 0;
}
}
public static boolean isLeapYear(int year) {
return (((year % 4 == 0) && !(year % 100 == 0)) || (year % 400 == 0));
}
public static boolean isValidDate(int month, int day, int year) {
return (month >= 1 && month <= 12) && (day >= 1 && day <= numDaysInMonth(month, isLeapYear(year))) && (year >= 0 && year <= maxYear);
}
}
If you have any questions I'll try my best to answer them!

The syntax of if-else statement on line 50 of your program is not correct.
It's a dangling else. Enclosing the body of if and else statement within braces should resolve this.
if (((year % 4 == 0) && !(year % 100 == 0)) || (year % 400 == 0))
{
numDays = 29;
system.out.println("is a leap year");
}
else
{
numDays = 28;
system.out.println("is not a leap year");
}
you can make use of IDE or give attention to compiler error message to resolve such errors.

asking user for another prompt after wrong input in java

so i'm asking the user for a month and a year. month has to be one of the twelve months and year has to be a number and no letters. i'm trying to figure out the best way to make the program say "wrong input, try again" and prompt them for input again. here's the section of code i'm working with for the month section.
public class MonthLength {
public static void main(String[] args) {
int month = 0;
// Prompt the user to enter a month
SimpleIO.prompt("Enter a month name: ");
String userInput = SimpleIO.readLine();
if (userInput.trim().toLowerCase().equals("january")) {
month = 1;
} else if (userInput.trim().toLowerCase().equals("february")) {
month = 2;
} else if (userInput.trim().toLowerCase().equals("march")) {
month = 3;
} else if (userInput.trim().toLowerCase().equals("april")) {
month = 4;
} else if (userInput.trim().toLowerCase().equals("may")) {
month = 5;
} else if (userInput.trim().toLowerCase().equals("june")) {
month = 6;
} else if (userInput.trim().toLowerCase().equals("july")) {
month = 7;
} else if (userInput.trim().toLowerCase().equals("august")) {
month = 8;
} else if (userInput.trim().toLowerCase().equals("september")) {
month = 9;
} else if (userInput.trim().toLowerCase().equals("october")) {
month = 10;
} else if (userInput.trim().toLowerCase().equals("november")) {
month = 11;
} else if (userInput.trim().toLowerCase().equals("december")) {
month = 12;
}
// Terminate program if month is not a proper month name
if (month < 1 || month > 12) {
System.out.println("Illegal month name; try again");
return;
}
and here's what i'm working with for the year section:
// Prompt the user to enter a year
SimpleIO.prompt("Enter a year: ");
userInput = SimpleIO.readLine();
int year = Integer.parseInt(userInput);
//Here, trying to use hasNextInt to make sure input is an integer
//If it's not, need to give an error message and prompt input again
// public boolean hasNextInt()
//Prompt input again if year is negative
if (year < 0) {
System.out.println("Year cannot be negative; try again");
return;
}
// Determine the number of days in the month
int numberOfDays;
switch (month) {
case 2: // February
numberOfDays = 28;
if (year % 4 == 0) {
numberOfDays = 29;
if (year % 100 == 0 && year % 400 != 0)
numberOfDays = 28;
}
break;
case 4: // April
case 6: // June
case 9: // September
case 11: // November
numberOfDays = 30;
break;
default: numberOfDays = 31;
break;
}
// Display the number of days in the month
System.out.println("There are " + numberOfDays +
" days in this month");
}
}
after seeing the code i'm sure it will be more clear what i'm asking. if they enter a word that isn't a month, prompt them and ask for input again. same thing if they enter a year that isn't integers. thanks in advance!

Running it in a loop, will do:
String userInput;
int month;
do{
SimpleIO.prompt("Enter a month name: ");
userInput = SimpleIO.readLine();
try{
month = Integer.parseInt(userInput);
} catch(NumberFormatException e){
continue;
}
}while(month <= 0 || month > 12);

You should create a loop that keeps prompting the user until the month is correctly inserted. Something in the following lines:
boolean correct_month = false; // Control variable
while(!correct_month)
{
int month = 0;
// Prompt the user to enter a month
SimpleIO.prompt("Enter a month name: ");
String userInput = SimpleIO.readLine();
...
// If the month is indeed correct
// then correct_month = true;
}
Then you apply the same idea to the years.
Instead of having all of those conditions on the month, I think it is better to add all the month strings into an ArrayList:
ArrayList <String> all_months = new ArrayList <String> ();
and then you just have to use all_months.indexOf with the string insert by the user. If it returns -1 the string is not a valid month, otherwise, it will give you the position where the month is on the list. For example
month = all_months.indexOf(userInput);
if(month != -1){
correct_month = true;
}
Thus, the complete solution would be something like:
ArrayList <String> all_months = new ArrayList <String> ();
all_months.add("january");
... // and so one
int month = 0; // Control variable
while(month <= 0)
{
// Prompt the user to enter a month
SimpleIO.prompt("Enter a month name: ");
String userInput = SimpleIO.readLine();
month = all_months.indexOf(userInput.trim().toLowerCase()) + 1;
}

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);