Attempt to invoke interface method 'boolean java.util.Set.addAll(java.util.Collection)' on a null object reference
49
What is a NullPointerException, and how do I fix it?
73034
StringBuilder append() and null values
36524
How can elements be added to a wildcard generic collection?
120566
Compare two objects in Java with possible null values
101146
Why can't I write Nullable>?
33103
How come invoking a (static) method on a null reference doesn't throw NullPointerException?
42612
Generics, arrays, and the ClassCastException
73120
Nullpointerexception when trying to send data from activity to class
99385
How to list all collections and their objects?
140738
Does setting Java objects to null do anything anymore?
106257
What are the possible problems caused by adding elements to unsynchronized ArrayList's object by multiple threads simultaneously?
137692
NullPointerException when working with arrays
59951
Why does list.append evaluate to false in a boolean context?
13711
java.lang.NullPointerException at org.glassfish.hk2.classmodel.reflect.impl.TypesImpl.getType
90115
How can I list the nodes for which a Boolean value is FALSE or NULL?
17784
Java if ternary operator and Collections.emptyList()
131552
new ArrayList() failing in Java