Null pointer exception at line 14

Question

I am getting null pointer exception at line 9 of my code I am fairly new to java can someone tell me the concept and mistakes I am doing.

public static void main(String[] args) {
    Certificate certificate1= new Certificate(60,"cnexirk","cbnifms",77);
    Certificate certificate2= new Certificate(45,"gphspvq","pqjbhmz",62);
    Certificate certificate3= new Certificate(41,"nfpxsmp","vimiopu",89);
    Certificate certificate4= new Certificate(95,"ionouca","bsbknpx",38);
    Certificate certificate5= new Certificate(39,"yhzrafu","itnbskb",44);
    Certificate[] objArray={certificate1,certificate2,certificate3,certificate4,certificate5};
    Certificate[] objResultArray1=getEven(objArray);
    for(Certificate certificate:objResultArray1){
        System.out.println(certificate.getId()+" " + certificate.getTitle()+" " + certificate.getDate()+" " + certificate.getRank()+" ");
    }


public static Certificate[] getEven(Certificate[] cer)
{
    Certificate[] objresult=new Certificate[cer.length];
    for(int i=0;i<cer.length;i++)
    {
        if(cer[i].getRank()==77)
        {
            objresult[i]=cer[i];
        }
    }
return  objresult;
}

} `

Since you only copy references to certificate where rank is 77, all the other array positions will have null reference values, so why are you confused that if fails when you try `certificate.getId()` when `certificate` is one of those null values? — Andreas, Feb 28 '19 at 19:54

score 0 · Accepted Answer · answered Feb 28 '19 at 19:53

The problem is here

if (cer[i].getRank() == 77) {
   objresult[i]=cer[i];
}

What if the rank isn't exactly 77? The array element remains null.
Then, when looping the returned array objResultArray1

certificate.getId()

throws the NullPointerException.

Your objResultArray1 array will look like

[Certificate@132u323, null, null, null, null]

Null pointer exception at line 14

1 Answers1