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Java Array of Objects How to Access and Print

I am entering data into two classes (Date and Task) that are array of objects (I believe that is what they are officially called) and part of a Day class. I can add data to the Task class using the setter and I can add data to the Date class using the setter. The question I have is how do I access that data entered into the Date and Task classes through the Day class that contains those objects. I am using the Tester class to enter the data into these classes. I can access and print the data for each date/task(s) combo right after I add the data to the classes by using the "System.out.println(day1);". However, I can only print the last data I entered into the classes. When I try to access the objects' data through the Day class, it is not showing anything.
I would expect my results to be the following:
2022/2/23
Description: Write code Hours: 2.5
Description: Research Hours: 1.5
For a total of 4.0 hours.
2022/2/24
Description: Read code Hours: 5.0
For a total of 5.0 hours.
But instead I just get the following error when I try to compile it using JGrasp:
Tester.java:28: error: cannot find symbol
for (i=0; i < day1.length; i++) {
^
symbol: variable length
location: variable day1 of type Day
Tester.java:29: error: incompatible types: String cannot be converted to Task[]
array = day1.getDate();
^
2 errors
How do I print out/access the objects in the Day class? I'm confused about how to do this in this context. When I use "System.out.println(day1);" I was assuming it would print out both of the sets of data I entered into the classes, but only the most recent one printed. I can print off the first data set entered by putting "System.out.println(day1);" after the first data set, but that is the only way it will print. It almost seems like I am writing over the top of the first set of data I add with the second set of data. Add to that I'm pretty unsure about how objects embedded within objects work. Thanks for your help! Here is the code:
public class Day implements Comparable {
public static final int MAX=50;
private Task[] tasks;
private int numTasks;
Date myDate;
Day myDay;
public Day(int year, int month, int day) {
myDate = new Date(year, month, day);
tasks = new Task[MAX];
numTasks = 0;
}
public void addTask(Task newTask) {
tasks[numTasks] = newTask;
numTasks++;
}
public int getNumTasks() {
return numTasks;
}
public String getDate() {
return myDate.toString();
}
public double getTotalHours() {
int i;
double sum;
sum = 0;
for (i=0; i < numTasks; i++)
sum += tasks[i].getHours();
return sum;
}
public String toString() {
String result;
int i;
result = myDate.toString()+"\n";
for (i=0; i < numTasks; i++)
result += tasks[i].toString()+"\n";
result += "For a total of "+getTotalHours()+" hours.";
return result;
}
//other getters and setters in this class too
}
public class Date implements Comparable {
private int year, month, day;
public Date (int inYear, int inMonth, int inDay) {
year = inYear;
month = inMonth;
day = inDay;
if (day > getNumDaysMonth(month, year) ||
month < 1 || month > 12) {
year = -1;
month = -1;
day = -1;
}
//other getters and setters below this
}
}
public class Task implements Comparable{
// field variables
private String description;
private double hours;
// constructors -> initialize all field variables - specialized method
public Task(String desc, double hrs) {
description = desc;
hours = hrs;
}
//other getters and setters below this
}
import java.util.Arrays;
public class Tester {
public static void main(String[] args) {
Day day1;
Task task1;
Task array[];
Day array2[];
double totalHours;
int n, i;
day1 = new Day(2022, 2, 23);
task1 = new Task("Write code", 2.5);
day1.addTask(task1);
task1 = new Task("Research", 1.5);
day1.addTask(task1);
n = day1.getNumTasks();
System.out.println("Number of tasks = "+n);
day1 = new Day(2022, 2, 24);
task1 = new Task("Read code", 5.0);
day1.addTask(task1);
System.out.println(day1);
System.out.println();
for (i=0; i < day1.length; i++) {
array = day1.getDate();
System.out.println(array);
}
totalHours = day1.getTotalHours();
System.out.println("Total hours = "+totalHours);
}
}

You're assigning "day1.getDate()", which is a String, to "array", which is a task array. These are not compatible. All you need to do is System.out.println(day1.getDate()); That would only print the same date day1.length times though. I suppose you want something from the day1 tasks. You probably want to implement a Task Day.getTask(int index) method to access them. It would be bad practice to return the whole task array, since the caller could then modify it. If you did want to implement a Task[] Day.getTasks() method, it should return a copy of the task array.

For the program mentioned above I am getting runtime error for one test case. All the remaining test cases are passed. Any suggestions

class Result {
public static String findDay(int month, int day, int year) {
String [] B = {"MONDAY","TUESDAY","WEDNESDAY","THURSDAY","FRIDAY","SATURDAY","SUNDAY"};
Calendar A = Calendar.getInstance();
A.set(Calendar.MONTH, month-1);
A.set(Calendar.YEAR, year);
A.set(Calendar.DAY_OF_MONTH,day);
return B[A.get(Calendar.DAY_OF_WEEK)-2];
}
}
I am getting run time error for the code mentioned above for one of the test cases. I don't understand why, can you please explain me how to resolve this kind of run time errors in the future.

I see 2 problems in this code, the both are about indexes.
I propose this version :
public static String findDay(int month, int day, int year) {
String [] B = {"MONDAY","TUESDAY","WEDNESDAY","THURSDAY","FRIDAY","SATURDAY","SUNDAY"};
Calendar A = Calendar.getInstance();
final int monthIndex = (month + 11) % 12;
A.set(Calendar.MONTH, monthIndex);
A.set(Calendar.YEAR, year);
A.set(Calendar.DAY_OF_MONTH,day);
final int dayIndex = (A.get(Calendar.DAY_OF_WEEK) + 5) % 7;
return B[dayIndex];
}
As you can see, I use the modulo to still in indexes range of your Array "B". I do the same for the "month index".

How can a User create dates in my Calender (java)?

I m currently trying to code a Calender with java.
I created 3 classes:
1. Date( includes year, month....)
2. Event(includes people, place, the class Date ... + an option to create dates )
3. Mainclass My mainclass that contains the menu.
My problem is that I don't know how the user is able to create his own date, because I have to create the object Termin myself... So, can somebody help me fix this? Thx in advance!
public class Event {
private String mDescription, mPlace, mNames;
private Date mStart, mEnd;
Termin(String description, String place, String names, Date start, Date end) {
mBetreff = description;
mOrt = place;
mNamen = names;
mBeginn = start;
mEnde = end;
}
public void create() {
Scanner read = new Scanner(System.in);
System.out.println("Enter 1. description 2. place 3. names 4. start 5. end ein");
mDescription = read.nextLine();
mPlace = read.nextLine();
mNames = read.nextLine();
}
public String toString() {
return "Description : " + mDescription + "\nPlace: " + mPlace + "\nNames: " + mNames + "\nIts starts at " + mStart
+ " and ends at " + mEnd;
}
}
public class Date {
private int year, day, month, hours, minutes;
Datum(int year, int month, int day, int hours, int minutes) {
this.day= day;
this.year= year;
this.month= month;
this.hours= hours;
this.minutes= minutes;
}
public String toString() {
return "\n" + day + "." + month + "." + year + " um " + hours+ ":" + minutes;
}
public void enterDate() {
}
}
EDIT:
I asked this question 2 years ago, back when I just started coding and had no idea of oop and encapsulation ...
To answer my own question, for every newbie that also tries to create a terminal calender:
Date needs the following methos:
public setDate() {
this.year = read.nextLine();
...
}
for every member.
Event takes the resulting object Date, either in the constructor or in a setter like method.

Creating an instance-method to create an appointment is kind of... strange since one needs to create an appointment (called Termin in your case) to create an appointment. One possibility would be the builder pattern. By having a public static inner builder class, you can set the constructor(s) private and enforce the use of that builder:
public class Main {
private int value;
private Main(int value) {
this.value = value;
}
public int getValue() {
return (this.value);
}
public static class MainBuilder {
boolean valueWasSet;
int value;
public MainBuilder() {
this.valueWasSet = false;
this.value = -1;
}
public void setValue(int value) {
this.value = value;
this.valueWasSet = true;
}
public Main build() {
if (!this.valueWasSet) {
throw new IllegalStateException("value must be set before a Main can be build.");
}
return (new Main(this.value));
}
}
}
(this is a simplified sketch to show the core mechanism on how to assert that certain values are set before constructing a Main through MainBuilder.
The process of constructing a Main would be:
MainBuilder builder = new MainBuilder();
builder.setValue(100);
// all following Main's will have a value of 100
Main mainOne = builder.build();
Main mainTwo = builder.build();
builder.setValue(200);
// all following Main's will have a value of 200
Main mainThree = builder.build();
Main mainFour = builder.build();

Confusion about java dates comparison

Pre-notes:
Yes, this is homework.
Our school's tutor is out for the day
My book is useless
I'm not exactly sure what to search for on google for help with my confusion...
Question:
Anyway - The question / confusion that I have involves the first bit of code that I have in my program to test the compareTo method.
Would I use the variables at the top of the code as my variables in the static void main area, or assign new variables, like I do have?
The values in public Date()... <-- Is that the date that my code in static void main is comparing to? (If so, I have a piece of code that I want to use that uses the current date, rather than what's in Date()).
I may have more questions later on, but I hope that someone can clear up my confusion better than my book or google has proven thus far.
Code:
package date;
import java.util.*;
public class Date implements Comparable
{
static Scanner console = new Scanner(System.in);
private int dMonth; //Part a of confusion 1
private int dDay;
private int dYear;
public Date()
{
dMonth = 1; //Confusion 2
dDay = 1;
dYear = 1900;
}
public Date(int month, int day, int year)
{
dMonth = month;
dDay = day;
dYear = year;
}
public void setDate(int month, int day, int year)
{
dMonth = month;
dDay = day;
dYear = year;
}
public int getMonth()
{
return dMonth;
}
public int getDay()
{
return dDay;
}
public int getYear()
{
return dYear;
}
public String toString()
{
return (dMonth + "." + dDay + "." + dYear);
}
public boolean equals(Object otherDate)
{
Date temp = (Date) otherDate;
return (dYear == temp.dYear
&& dMonth == temp.dMonth
&& dDay == temp.dDay);
}
public int compareTo(Object otherDate)
{
Date temp = (Date) otherDate;
int yrDiff = dYear - temp.dYear;
if (yrDiff !=0)
return yrDiff;
int monthDiff = dMonth - temp.dMonth;
if (monthDiff !=0)
return monthDiff;
return dDay - temp.dDay;
}
public static void main(String[] args) //Part b of confusion 1
{
int month;
int day;
int year;
Date temp;
System.out.print("Enter date in the form of month day year");
month = console.nextInt();
day = console.nextInt();
year = console.nextInt();
System.out.println();
}
}

As mentioned in the comments, I think you need to read about the difference between static methods/attributes and the ones in instances. I think this is what you should be doing in the main method:
System.out.print("Enter date in the form of month day year");
Date date1 = new Date(console.nextInt(), console.nextInt(), console.nextInt());
System.out.print("Enter second date in the form of month day year");
Date date2 = new Date(console.nextInt(), console.nextInt(), console.nextInt());
System.out.println("Comparison result:");
System.out.println(date1.compareTo(date2));
Regarding your confusion points:
Class attributes
private int dMonth; //Part a of confusion 1
private int dDay;
private int dYear;
These are special variables. Each instance (that is, every object created with new Date) has its own value for dMonth, dDay and dYear. It is not accessible from the main because main is a static method, and thus doesn't have access to instance variables.
If you didn't understand, at least you know the names to search further.
Default constructor
public Date()
{
dMonth = 1; //Confusion 2
dDay = 1;
dYear = 1900;
}
Those values are used when you create a new Date object without specifying which month/day/year you want. So new Date(2, 3, 2013) means 2/3/2013, while new Date() means 1/1/1900.

No you can't, dMonth, dDay and dYear are member variables. If you want to use them directly inside your main method you will have to use the keyword static so that they become class variables. But no, that is not what you want.
Your main method is doing nothing useful really. Your confusion point 2 is a constructor:
Date d = new Date(); // Data Instance -> First constructor
d.getMonth(); // 1
d.getDay(); // 1
d.getYear(); // 1900
Date d2 = new Date(2, 2, 1901);
d2.getMonth(); // 2
d2.getDay(); // 2
d2.getYear(); // 1901
d2.setDate(3, 3, 1902);
d2.getMonth(); // 3
d2.getDay(); // 3
d2.getYear(); // 1902
d.getMonth(); // Still 1 since member variables of d are independent of d2
d.compareTo(d2); // -2 -> (1900 - 1902)
You can create date instances inside your main method and use code like the one above to access member variables (probably the whole point of your exercise).

Compare two objects, and return string. But one object doesn't take parameters?

This is homework.
GOAL: I want to compare the date of two objects to decide whether my person object is an adult or not and store this in a string.
The strange thing is, all my values of date d1 are 0;
public class Date {
public int day, month, year;
public String child
Date(date d1, date d2) {
if ((d1.year - d2.year > 18) ||
((d1.year - d2.year == 18) && (d2.year> d1.year)) ||
((d1.year - d2.year == 18) && (d2.year == d1.maand) && (d2.day > d1.day))) {
child = adult;
} else {
child = child;
}
Date(int a, int b, int c) {
a = year;
b = month;
c = day;
}
Date (String birthdate) {
String pattern = "\\d{2}-\\d{2}-\\d{4}";
boolean b = birthdate.matches(pattern);
if (b) {
String[] str = birthdate.split("-");
for (String s: str)
this.day = Integer.parseInt(str[0]);
this.month = Integer.parseInt(str[1]);
this.year = Integer.parseInt(str[2]);
this.child = false;
} else {
System.out.println("Wrong format");
}
}
When I make a test, this happens:
System.out.println("D1 year = " + d1.year);
System.out.println("D1 day = " + d1.day);
System.out.println("D1 month = " + d1.month);
Result:
D1 year = 0
D1 day = 0
D1 month = 0
Why does this happen? Lets look at my other class.
My other class, where my method infoPerson is located is as following:
public static Person infoPerson() {
String name, lastname, birthdate;
Datum birthday, today;
System.out.println("Firstname:");
name = userInput();
System.out.println("Lastname:");
lastname = userInput();
System.out.println("Birthdate?:");
birthdate = userInput();
//here I send the string birthdate to my Date class
birthday = new Date(birthdate);
today = new Date(3, 7, 2013);
//Here I want to compare my two Date objects, today and birthday. This is were I got stuck, how do I do this correctly?
dateChild = new Date(today, birthday);
// here i send the new date to my Person class what consists of two strings and Data birthday
return new Gast(name, lastname, dateChild);
}

The assignment in the constructor is reversed:
Date(int a, int b, int c) {
a = year; // should be year = a;
b = month; // month = b;
c = day; // day = c;
}
Please don't use the class name same as the one defined in Java API. Date is already a class in java.util package.
Apart from that there are many compiler errors in your code:
public string child - isn't going to compile. Should be String not string.
void compareTo(date d1, date d2) - I don't know what you're trying to do here. But this too won't compile. Undefined type - date
You've declared the Datum birthday and initializing it using new Date(...). That too wouldn't work.
For some reason, I feel like you don't have any method in your class, but just a bunch of constructors. My suggestion would be - throw that code away, and start afresh.
And please don't use a bunch of integer fields to store birthdays. Use a Calendar instance instead.