How do I convert from int to Long in Java?

Question

I keep finding both on here and Google people having troubles going from long to int and not the other way around. Yet I'm sure I'm not the only one that has run into this scenario before going from int to Long.

The only other answers I've found were "Just set it as Long in the first place" which really doesn't address the question.

I initially tried casting but I get a "Cannot cast from int to Long"

for (int i = 0; i < myArrayList.size(); ++i ) {
    content = new Content();
    content.setDescription(myArrayList.get(i));
    content.setSequence((Long) i);
    session.save(content);
}

As you can imagine I'm a little perplexed, I'm stuck using int since some content is coming in as an ArrayList and the entity for which I'm storing this info requires the sequence number as a Long.

Solution 1

Note that there is a difference between a cast to long and a cast to Long. If you cast to long (a primitive value) then it should be automatically boxed to a Long (the reference type that wraps it).

You could alternatively use new to create an instance of Long, initializing it with the int value.

Solution 2

Use the following: Long.valueOf(int);.

Solution 3

If you already have the int typed as an Integer you can do this:

Integer y = 1;
long x = y.longValue();

Solution 4

use

new Long(your_integer);

or

Long.valueOf(your_integer);

Solution 5

 1,new Long(intValue);
 2,Long.valueOf(intValue);

View more solutions

Comments

[Instantsoup]

for (long i = 0; i < myList.size(); ++i) works too

[Ghosty]

@Instantsoup Yes that will work for the loop, but as I specified at the bottom of my question the ArrayList I'm working with requires the primitive int when specifying what index position to get

[Daniel Jipa]

long longValue = intValue | 0L;

[Eric]

What I did is: cast int to long first, then assign long to Long. e.g int x = 2; Long y = (long)x;

[Grundlefleck]

To demonstrate what Earwicker said you could call Long.valueOf(i), which takes a long but will widen an int and give you back a Long object.

[palantus]

Autoboxing is preferable, because it doesn't necessarily have to create a new Long object every time.

[Grundlefleck]

(Warning: the rest of this comment is guesswork and conjecture) If the values given to Long.valueOf() fall between 0 and 128, which is very common, and it returns a cached instance, will that be preferable over autoboxing? (I may ask a new question if you think it's worth it...)

[Daniel Earwicker]

Autoboxing does the same thing as that. By the way, it's between -127 and 128.

[palantus]

@Grundlefleck: Autoboxing uses Long.valueOf() (if I remember correctly), so there wouldn't be a difference at all. My comment was in reply to the answer, not to your comment.

[Grundlefleck]

@mmyers: ah I see, cheers. @Earwicker: may I be so bold to suggest there's some information in these comments that would earn your answer at least another +1 were it to be included? :-)

[Daniel Earwicker]

@Grundlefleck - thanks, but would probably make more sense on a question about what autoboxing is equivalent to, e.g. you could upvote this answer: stackoverflow.com/questions/766468/…

[will824]

Look out, as this will generate a NullPointerException if you are receiving a Integer object which is null.

[Daniel Earwicker]

if jPaidCountSpinner.getValue() returns an Object that is in fact a Long, you definitely only need to put a (Long) cast in front. Also try putting a breakpoint on your check for int.class or long.class etc. Does it ever hit it? And if you have a number-like object, it will support java.util.Number, so cast it to that and call the longValue method. No need to go via a string in that case. So this function could be simplified quite a bit, even if you also need to deal with strings. (Part of the problem here is the bad reference documentation for JSpinner).

[shareef]

correct if am wron i thought may be the answer is old becuse i cant find the method Long.valueOf(int) !!

[Rondo]

@will824 - a primitive 'int' variable cannot be null.

[Rondo]

@shareef - see serg's comment - but I think this method casts the int to a long which autoboxes with a Long... so seems redundant

[Salem]

@Rondo an Integer can, which is what he said.

[Rondo]

@1blustone either way, it is a red herring: if an Integer was received then a nullpointer would not be generated by this call but by the attempt to get the number into the required primitive: long (Long.valueOf(int) doesn't exists)

[Profiterole]

I too ended up doing something like this. I wasn't sure what kind of number I would receive and was willing to convert it to Long with little concern for efficiency but wanting to avoid boilerplate.

[Martin Schröder]

longValue is just a (long), so the only thing you "gain" here is Integer's internal cache.

[Farid]

There is no such method in Java, you mistook it for Long.valueOf(long)

[syd]

yeah. how about just (long) intValue ?