java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object referenc

Question

When I want to chat with any user in my application, I get this error, what do you think is the reason?

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
        at com.hiddy.katana.user.ChatActivity$11.onDataChange(ChatActivity.java:441)

My code

if (Objects.requireNonNull(modelChat).getReceiver().equals(myId) && modelChat.getSender().equals(hisUid)) {
                        HashMap<String, Object> hashMap = new HashMap<>();
                        hashMap.put("isSeen", true);
                        snapshot.getRef().updateChildren(hashMap);

Why do you assume `Objects.requireNonNull(modelChat).getReceiver()` doesn't return null? — Scott Hunter, May 25 '22 at 19:36

score 1 · Answer 1 · edited May 26 '22 at 05:55

According to your code either this returns null

Objects.requireNonNull(modelChat).getReceiver()

or this

modelChat.getSender()

You can check whether they return null or not before using:

String receiver = Objects.requireNonNull(modelChat).getReceiver();
String sender = Objects.requireNonNull(modelChat).getSender();

if (receiver != null && receiver.equals(myId) && sender != null && sender.equals(hisUid)) {
    HashMap<String, Object> hashMap = new HashMap<>();
    hashMap.put("isSeen", true);
    snapshot.getRef().updateChildren(hashMap);
}

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object referenc

1 Answers1