Use of Java Ternary Operator with ==

You cannot use a ternary operator in a statement context. It is only allowed as an expression. You have two options:

1. Use an if statement:

   if (numArray[i] % 2 == 1) {
       oddList.add(numArray[i]);
   } else {
       evenList.add(numArray[i]);
   }
   

2. Restructure the ternary operator (does not work in general, but removes some duplication in this case):

   (numArray[i] % 2 == 1 ? oddList : evenList).add(numArray[i]);
   

In addition to previous comment. Java program consists of statements. In you case numArray[i] % 2 == 1 ? oddList.add(numArray[i]) : evenList.add(numArray[i]); is part of ConditionalExpression. ConditionalExpression must be part same statement for example Assigment or ReturnStatement.

Thus you can use this, because List.add() returns boolean value:

1. Assigment boolean b = numArray[i] % 2 == 1 ? oddList.add(numArray[i]) : evenList.add(numArray[i]);

2. Return

   return numArray[i] % 2 == 1 ? oddList.add(numArray[i]) : evenList.add(numArray[i]);

3. Another statement with boolean value...