Checking for int in int array

Question

I'm trying to find an integer inside of an int[] array and return true or false depending on whether or not it's present anywhere, however my code, which I've taken from numerous websites.

My array is as follows:

private static final int[] thirtyOneDays = {1, 3, 5, 7, 8, 10, 12};

And I'm searching it like so:

Arrays.asList(thirtyOneDays).contains(month)

Where month is an integer.

When debugging the program all the variables and fields are set correctly as expected, it just always returns false. Does anyone know why this is?

As for month, it originates from a JTextField on my GUI:

new Validate(txtDay.getText(), txtMonth.getText(), txtYear.getText());

Here's the Validate constructor:

public Validate(String day, String month, String year)
{
    instance = this;

    if(this.isYearValid(year))
    {
        if(this.isMonthValid(month, year))
        {
            if(this.isDayValid(day, month, year))
            {
                isAllValid = true;
            }
        }
    }
}

And here's the very top of isDayValid():

private boolean isDayValid(String dayS, String monthS, String yearS)
{
    int year = Integer.parseInt(yearS);
    int month = Integer.parseInt(monthS);
    int day = Integer.parseInt(dayS);

~~~~~~~ P.S. What's the difference between:

int[] intArray = {1, 2, 3}
int[] intArray = new int{1, 2, 3, 4}
Integer[] intArray = new Integer{1, 2, 3, 4}

@SirRichie it's inputted by the user and then fed to the constructor of another class where it's fed to this method and converted from string to integer (successfully) — Jake Stanger, Nov 18 '14 at 17:46
have a look here http://stackoverflow.com/questions/1073919/how-to-convert-int-into-listinteger-in-java — user902383, Nov 18 '14 at 17:50

Reimeus · Answer 1 · 2014-11-18T20:43:43.573

3

Arrays.asList(thirtyOneDays) returns a List containing a single entry of type int[] which is different from any of the integers in the original List.

edited Nov 18 '14 at 20:43

answered Nov 18 '14 at 17:42

Reimeus

158,255
15
216
276

Could you explain this in more depth please? My knowledge around arrays is pretty weak. – Jake Stanger Nov 18 '14 at 17:47
maybe you should add for clarification, that return type of `asList` will be `List` an not `List` in this case – JohnnyAW Nov 18 '14 at 17:48
Wow, I never noticed this subtle detail - definitely deserves an upvote. – SirRichie Nov 18 '14 at 17:57

James Hutchinson · Accepted Answer · 2014-11-18T17:57:18.093

Try this instead:

    for(int x:thirtyOneDays) {
        if (x == month) {
            return;
        }
    }

You are trying to compare an array of integers with a single integer. So it's a bit like saying is this pen like this group of ten pens. The answer is always going to be no.

Regarding this bit:

int[] intArray = {1, 2, 3}
int[] intArray = new int{1, 2, 3, 4}
Integer[] intArray = new Integer{1, 2, 3, 4}

int is a base type that you can't call methods on, whereas Integer is a wrapper class that allows you to essentially call methods.

I'm not sure what the difference between the first two lines is, but I suspect it concerns how Java allocates memory.

Thanks. This answer is quite simple and easy to understand and worked straight away. — Jake Stanger, Nov 18 '14 at 18:01

score 0 · Answer 3 · answered Nov 18 '14 at 17:50

0

int[] is an array of primitvs. Where Integer[] is an array of Integer objects. Thus it size is different. It is not the same type at all.

answered Nov 18 '14 at 17:50

Jörg Bächtiger

120
1
4

score 0 · Answer 4 · answered Nov 18 '14 at 17:58

Or try this. With a while-loop and a boolean expression you don't have to iterate thru the whole array.

boolean match = false;
int index = 0;
while(!match && index < thirtyOneDays.length) {
    if(thirtyOneDays[index] == month) {
        match = true;

        //do what u want with the matching int
    }
index++;
}

Checking for int in int array

4 Answers4