How to check if array element is null to avoid NullPointerException in Java

Question

I have a partially nfilled array of objects, and when I iterate through them I tried to check to see whether the selected object is null before I do other stuff

Answer 1

Fighting whether the code is compiling or not I would say create a array of sixe 5 add 2 values and print them , you will get the two values and others are null. The question is although the size is 5 but there are 2 objects in the array . How to find how many objects are present in the array

Answer 2

You can do it on one line of code (without array declaration):

object[] someArray = new object[] 
{
    "aaaa",
    3,
    null
};
bool containsSomeNull = someArray.Any(x => x == null);

Answer 3

The example code does not throw an NPE. (there also should not be a ';' behind the i++)

Answer 4

String labels[] = { "MH", null, "AP", "KL", "CH", "MP", "GJ", "OR" }; 

if(Arrays.toString(labels).indexOf("null") > -1)  {
    System.out.println("Array Element Must not be null");
                     (or)
    throw new Exception("Array Element Must not be null");
}        
------------------------------------------------------------------------------------------         

For two Dimensional array

String labels2[][] = {{ "MH", null, "AP", "KL", "CH", "MP", "GJ", "OR" },{ "MH", "FG", "AP", "KL", "CH", "MP", "GJ", "OR" };    

if(Arrays.deepToString(labels2).indexOf("null") > -1)  {
    System.out.println("Array Element Must not be null");
                 (or)
    throw new Exception("Array Element Must not be null");
}    
------------------------------------------------------------------------------------------

same for Object Array    

String ObjectArray[][] = {{ "MH", null, "AP", "KL", "CH", "MP", "GJ", "OR" },{ "MH", "FG", "AP", "KL", "CH", "MP", "GJ", "OR" };    

if(Arrays.deepToString(ObjectArray).indexOf("null") > -1)  {
    System.out.println("Array Element Must not be null");
              (or)
    throw new Exception("Array Element Must not be null");
  }

If you want to find a particular null element, you should use for loop as above said .

Answer 5

You have more going on than you said. I ran the following expanded test from your example:

public class test {

    public static void main(String[] args) {
        Object[][] someArray = new Object[5][];
        someArray[0] = new Object[10];
        someArray[1] = null;
        someArray[2] = new Object[1];
        someArray[3] = null;
        someArray[4] = new Object[5];

        for (int i=0; i<=someArray.length-1; i++) {
            if (someArray[i] != null) {
                System.out.println("not null");
            } else {
                System.out.println("null");
            }
        }
    }
}

and got the expected output:

$ /cygdrive/c/Program\ Files/Java/jdk1.6.0_03/bin/java -cp . test
not null
null
not null
null
not null

Are you possibly trying to check the lengths of someArray[index]?

Answer 6

It does not.

See below. The program you posted runs as supposed.

C:\oreyes\samples\java\arrays>type ArrayNullTest.java
public class ArrayNullTest {
    public static void main( String [] args ) {
        Object[][] someArray = new Object[5][];
            for (int i=0; i<=someArray.length-1; i++) {
                 if (someArray[i]!=null ) {
                     System.out.println("It wasn't null");
                 } else {
                     System.out.printf("Element at %d was null \n", i );
                 }
             }
     }
}


C:\oreyes\samples\java\arrays>javac ArrayNullTest.java

C:\oreyes\samples\java\arrays>java ArrayNullTest
Element at 0 was null
Element at 1 was null
Element at 2 was null
Element at 3 was null
Element at 4 was null

C:\oreyes\samples\java\arrays>