Java check if array[] item exists

Question

I am downloading some data into a String array. Let's say ImageLinks. How do I check if a item in array exist?

I am trying

if(ImageLinks[5] != null){}

but it gives me ArrayIndexOutOfBoundsException. (Because there are really no 5 link in the array)

if (ImageLinks.length > 5) ??

Peter Lawrey
– Peter Lawrey

2012-10-15 14:20:08 +00:00
Commented Oct 15, 2012 at 14:20 — Peter Lawrey
– Peter Lawrey, Commented Oct 15, 2012 at 14:20

Baz · Accepted Answer · 2012-10-15 14:33:25Z

38

To prevent the ArrayIndexOutOfBoundsException, you can use the following:

if(ImageLinks.length > 5 && ImageLinks[5] != null)
{
    // do something
}

As the statements in the if are checked from left to right, you won't reach the null check if the array doesn't have the correct size.

It's quite easy to generalise for any scenario.

edited Oct 15, 2012 at 14:33

answered Oct 15, 2012 at 14:19

Baz

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3 Comments

sdlins Over a year ago

What about an array where you set the indexes? Like in a[0] = 20; a[5] = 30;. If I check if(a.length > 4 && a[4] != null) it throws a null exception, doesn't?

Baz Over a year ago

@sdlins To be able to set index 5, the array has to have a length of at least 6 before you get to the if statement. At that point it'll check if the index exists and whatever it is null. There won't be any exception.

sdlins Over a year ago

Yeah! Sorry, you are right! I tried by code it and it works fine. I was probably mixing different languages concepts. Thanx!

Vivek · Accepted Answer · 2018-07-06 08:21:03Z

8

Write a static function

public static boolean indexInBound(String[] data, int index){
    return data != null && index >= 0 && index < data.length;
}

Now, give it a call in your code

if(indexInBound(ImageLinks, 5) && ImageLinks[5] != null){
   //Your Code
}

edited Jul 6, 2018 at 8:21

answered Oct 15, 2012 at 14:25

Vivek

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7 Comments

Baz Over a year ago

This will not take care of the null case.

Vivek Over a year ago

@Baz This is addressing the ArrayIndexOutOfBoundsException, if we want to handle Null Condition we can anytime add one more catch block for NullPointerException

Baz Over a year ago

Just saying that OP wants to achieve both.

Vivek Over a year ago

That is also right, there isn't any statement in the code throwing a NPE.

CosmicGiant Over a year ago

I got a few issues with this answer... 1) Exceptions should be used for exceptional behavior; using exceptions to handle expected behavior, such as in a true or false check, is very bad. 2) is...Exists is bad naming.

|

kosa · Accepted Answer · 2012-10-15 14:19:35Z

6

Make sure array is of that length before doing lookup

if(ImageLinks.length > 5 && ImageLinks[5] != null){}

answered Oct 15, 2012 at 14:19

kosa

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Comments

Raja Jawahar · Accepted Answer · 2018-07-05 05:15:55Z

1

The reason its fails is the array has less than 6 elements.

Check first the array has correct number of elements, and then check the element exists in array.

 if (ImageLinks.length > 5 && ImageLinks[5] != null) {
     // do something
 }

edited Jul 5, 2018 at 5:15

Raja Jawahar

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answered Jan 13, 2017 at 22:17

Edward Vaghela

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3 Comments

Jarrod Sears Over a year ago

Your answer is not correct. Refer to the "short-circuiting" logic on the following Java documentation page: docs.oracle.com/javase/tutorial/java/nutsandbolts/op2.html

Jarrod Sears Over a year ago

if the first boolean statement is false and there is an && operator after it, there is no reason to continue evaluation as the entire statement must at that point be false regardless of whether or not the 2nd operand is true or false

Neil Over a year ago

Corrected the answer

Alexis Gamarra · Accepted Answer · 2020-05-24 07:23:28Z

0

if (ImageLinks != null && Stream.of(ImageLinks).anyMatch(imageLink-> imageLink != null)) {
//An item in array exist
}

answered May 24, 2020 at 7:23

Alexis Gamarra

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Comments

banjara · Accepted Answer · 2012-10-15 14:19:47Z

-1

yes there are less than 6 elements ImageLinks[5] refers to 6th element as array index in java starts from 0

answered Oct 15, 2012 at 14:19

banjara

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