CODEWITHSUNDEEP
javaandroidjsongson
I wrestled a bear once.
I wrestled a bear once.

Reputation: 23379

Checking for null values in Java

I'm trying to modify an Android app that is pulling some JSON from a server..

JSONObject mResult = new JSONObject((String) result);

Then using that to construct an object from my Sponsor class..

Gson mGson = new Gson();
mSponsor = mGson.fromJson(mResult.getJSONObject("data").getJSONObject("sponsor").toString(), Sponsor.class);

Sponsor class is just a shell with setters and getters, no logic done. Something like this:

public class Sponsor {

    @SerializedName("address1")
    private String Address1;
    @SerializedName("address2")
    private String Address2;

    public Sponsor(String address1, String address2) {
        Address1 = address1;
        Address2 = address2;
    }

    public Sponsor() {
        Address1 = "";
        Address2 = "";
    }

    public String getAddress1() {
        return Address1;
    }

    public void setAddress1(String address1) {
        Address1 = address1;
    }

    public String getAddress2() {
        return Address2;
    }

    public void setAddress2(String address2) {
        Address2 = address2;
    }
}

The app puts the address in a TextView like so:

txtAddress = (TextView) view.findViewById(R.id.txt_sponsor_address);
txtAddress.setText(mSponsor.getAddress1() + "\n" + mSponsor.getAddress2());

This all works, except when the server returns null for address2, in which case the literal text "null" is printed in the TextView where address2 should be.

My question is how can i get rid of the "null"?

I've tried a few different things, started with a simple ternary statement and got more and more verbose and nothing has worked so for.

Here is the latest and most ridiculous-looking thing I've tried so far:

String addr2 = ((String) mSponsor.getAddress2()).trim();
String a2;
if((addr2 == "null") || (addr2 == "")) a2 = (String) "";
else a2 = (String) addr2;

txtAddress.setText(mSponsor.getAddress1() + "\n" + a2);

This causes the app to crash when I open that Activity.

I'm a noob at Java so please provide references if you can.

Upvotes: 1

Views: 137

Answers (6)

tale852150
tale852150

Reputation: 1628

Try this for your getter code:

 public String getAddress2() {
    if (Address2.equals("null")) {
        Address2="";
    }
    return Address2;
 }

Of course, you can do the same with your other getter for Address1. Also, if you want to check for an empty string, use Address2.length() == 0 as opposed to Address2 == "".

Upvotes: 0

Udayaditya Barua
Udayaditya Barua

Reputation: 1162

String addr2 = mSponsor.getAddress2();
if(!TextUtils.isEmpty(addr2) || !addr2.equalsIgnoreCase("null")
     txtAddress.setText(mSponsor.getAddress1() + "\n" + addr2);
else
     txtAddress.setText(mSponsor.getAddress1());

Upvotes: 1

tkhm
tkhm

Reputation: 880

How about this? 

// if null, addr2="", if not null, addr = getAddress2()'s result 
String addr2 = mSponsor.getAddress2() == null ? "" : ((String) mSponsor.getAddress2()).trim();

txtAddress.setText(mSponsor.getAddress1() + "\n" + addr2);

Upvotes: 1

DeeV
DeeV

Reputation: 36035

"getAddress2()" isn't returning the literal string "null". It's returning a null reference and the StringBuilder is converting it to a "null" String when you print it in the concatenation. That's why it crashes when you try to trim the word.

A simple way to fix it is to put the ternary operator in the getter itself like so:

public String getAddress2() {
  return (Address2 == null) ? "" : Address2;
}

Now you'll never return a null reference and you can safely use it without any checks.

Upvotes: 3

Chol
Chol

Reputation: 2117

You should not use :

if((addr2 == "null")

For string comparaison use:

if (addr2.equalsIgnoreCase("null"))

Upvotes: 1

NSimon
NSimon

Reputation: 5287

You could create another getter in your Sponsor class, where you'd put your logic to get a formatted address : 

public String getFormattedAddress() {
    if (!TextUtils.isEmpty(Address1) && !TextUtils.isEmpty(Address2)
        && !Address1.equalsIgnoreCase("null") && !Address2.equalsIgnoreCase("null")) {
      return (Address1 + "\n" + Address2);
    }
    if (!TextUtils.isEmpty(Address1) && !Address1.equalsIgnoreCase("null")) {
      return (Address1);
    }
    if (!TextUtils.isEmpty(Address2) && !Address2.equalsIgnoreCase("null")) {
      return (Address2);
    }
    return ("");
}

And then simply setText with :

txtAddress.setText(mSponsor.getFormattedAddress());

Upvotes: 3

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