How to enter a LocalDate value into BlueJ “Create

问题:

I'm not trying to format the date in YYYY-MM-DD or dd/MM/YYYY. I'm asking about the literal format of LocalDate.

I just started learning Java and I am using this IDE called BlueJ. and I want to create a test method.

The screenshot will show what I am trying to do

Now since from the constructor we know that it requires a int, LocalDate and a double. I've searched online and found that

https://www.javabrahman.com/java-8/java-8-working-with-localdate-localtime-localdatetime-tutorial-with-examples/

java.time.LocalDate: A LocalDate instance holds a date without a time zone, in ISO-86011 calendar system. LocalDate has the default format ‘YYYY-MM-DD’ as in ‘2016-12-12’.

So I would put a normal number in 10001 for the testID and double would be something like 50.5 I also know that for it to register a string (if it was needed) I would need to enclose it within "string"

But I've tried all sorts of way to put in the date and I would be left with an error

2018-05-30,30-05-2018,30/05/2018 would give me

Error: incompatible types: Int cannot be converted to java.time.LocalDate

"30/05/2018" on the other hand would give me

Error: Incompatible types: java.lang.String cannot be converted to java.time.LocalDate

If I try 30.05.2018 it would say

Error: ';' expected

If I try '2018-05-30' it would say

Error: unclosed character literal

I ran out of ways to try it. So if you could tell me how I should put it in there, that would be great.

I just really need to know how BlueJ wants me to input it. Cause the resources for BlueJ is so sparse online.

---

Code:

import java.time.LocalDate;
import java.util.ArrayList;
/**
 * Write a description of class TestPaper here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class TestPaper
{
    // instance variables - replace the example below with your own
    private int testID;
    private LocalDate testDate;
    private double testMarks;
    private ArrayList<MCQ> MCQDetails;

    /**
     * Constructor for objects of class TestPaper
     */
    public TestPaper(int testID, LocalDate testDate, double testMarks)
    {
        this.testID = testID;
        this.testDate = testDate;
        this.testMarks = testMarks;
        MCQDetails = new ArrayList<MCQ>() ; 
    }

/**
 * Accessor Method getTestID to get the testID
 *
 * @return int value of the choice ID
 */
public int getTestID(){
    return testID;
}

/**
 * Mutator Method to set the testID
 * 
 *  @param int format of the testID to set
 */
public void setTestID(int testID){
    this.testID = testID;
}

/**
 * Accessor Method getTestMarks to get the Test Marks
 *
 * @return double value of the test marks 
 */
public double getTestMarks(){
    return testMarks;
}

/**
 * Mutator Method to set the testMarks
 * 
 *  @param String format of the choice Description to be set
 */
public void setTestMarks(double testMarks){
    this.testMarks = testMarks;
}

    /**
 * Accessor Method getTestDate to get the testDate
 *
 * @return LocalDate value of the testDate
 */
public LocalDate getTestDate(){
    return testDate;
}

/**
 * Mutator Method to set the testDate
 * 
 *  @param LocalDate format of the testDate to set
 */
public void setTestDate(LocalDate testDate){
    this.testDate = testDate;
}

/**
 * Method addMCQ will allow users to add a MCQ Object to the list of MCQ
 *
 * @param addMCQ a MCQ Object
 * @return boolean will return true if it is successfully added or false if not
 */
public boolean addMCQ(MCQ MCQName)
{
    return MCQDetails.add(MCQName);
}

/**
 * Method removeMCQ to remove an MCQ object from the Arraylist
 *
 * @param MCQName A parameter of type MCQ 
 */
public void removeMCQ(MCQ MCQName)
{
    MCQDetails.remove(MCQName);
}

/**
 * Method listMCQ to return a list of MCQ arraylist
 *
 * @return The return value of MCQDetails (MCQ Arraylist)
 */
public ArrayList<MCQ> listMCQ()
{
    return MCQDetails;
}

    public MCQ findMCQ(int MCQID)
{
    for(MCQ m : MCQDetails)
    {
        if(m.getQuestionID() == MCQID)
        {
            return m;
        }
    }
    return null;
}

回答1:

Include package

As discussed in the comments, the solution is to add the code that creates the LocaDate, but bluej needs the fully qualified class name with the package prefix “java.time.”:

java.time.LocalDate.of(2018, 5, 30)

Not sure why it doesn't work with just LocalDate.of(...) (even with the class correclty imported), but at least this works.

---

Just another detail: a date has no format. Classes like LocalDate just holds values (in this case, it has year, month and day values), but a date itself has no format at all. The same date can be represented in many different formats: May 30th 2018, 2018-05-30, 30/05/18 are different formats, but all represent the same date. A date object just holds the values, and you can choose whatever format you want to represent it.

When you print a LocalDate, it implicity calls toString(), which by default chooses yyyy-MM-dd format, which is a ISO 8601 format, but as I said, that's just one of the many possible ways to format a date (although the value always stays the same). Telling that "a date has a format" is wrong and misleading.

回答2:

Try converting the LocalDate in the call, such as:

TestPaper (2018-05-30, LocalDate.parse("2018/05/30"), 30/05/2018);

There are other static methods within LocalDate you can use. See here for more examples.

From your comment above, don't forget your import:

import java.time.LocalDate;