Check if element in object is null

Question

I have a simple dataset class similar to:

class DataSet {
    private String value;
    private String additionalValue;

    public DataSet(String value, String additionalValue) {
        this.value = value;
        this.additionalValue = additionalValue;
    }

    public String getAdditionalValue() {
        return this.additionalValue;
    }
}

Then I have created an ArrayList<DataSet> and added a new element DataSet("Value1", null).

Now at some point I need to check if the entry with value "Value1" has additionalValue and if it does, what it is.

I do a simple loop checking if value.equals("Value1") == true, then I do:

if (element.getAdditionalValue() != null) {
    return element.getAdditionalValue();
}

However, as soon as it gets to the if statement, it throws an error saying that the value is null. How can I make it so that it doesn't throw an error and just skips the return statement if additionalValue is null?

EDIT:

But the thing is that the element cannot be null at the point where it checks additionalValue as it passed through the element.getValue.equals("Value1") condition.

for (DataSet element : dataSet) {
    if (element.getValue.equals("Value1")) {
        if (element.getAdditionalValue() != null) {
            return element.getAdditionalValue();
        }
     }
}

if ( element != null && element.getAdditionalValue() != null) { your code here} ... — Dave Richardson, Jul 13 '12 at 12:59
`if(value.equals("Value1") == true)` can be written as `if(value.equals("Value1"))` — ant, Jul 13 '12 at 13:00
If value is null, calling .equals on it will throw. Instead call .equals on the string and check against value. — Dave Newton, Jul 13 '12 at 13:00
Based on the above, it seems to me you could get NullPointerException when checking with equals. Try to substitute it with `"Value1".equals(value)`. Also, `== true` is needless. — Andrew Logvinov, Jul 13 '12 at 13:01
Or, if it's the other if statement... if("Value1".equals(value)) {} avoids the need to check for null — Dave Richardson, Jul 13 '12 at 13:02

score 21 · Accepted Answer · answered Jul 13 '12 at 13:00

21

I think the problem is that your element object is null, so you have to check it before checking additionalValue.

if (element != null && element.getAdditionalValue() != null){
   return element.getAdditionalValue();
}

answered Jul 13 '12 at 13:00

davioooh

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score 3 · Answer 2 · answered Jul 13 '12 at 13:01

3

This will sort you out:

if (element != null && element.getAdditionalValue() != null) {
    return element.getAdditionalValue();
}

answered Jul 13 '12 at 13:01

duffymo

305,152
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If `element == null` can `element.anythingElse()` be anything but null? – Mob Jul 13 '12 at 13:04
4

@Mob no, and thats why shortcircuit compare is used – NimChimpsky Jul 13 '12 at 13:05

Check if element in object is null

2 Answers2