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ba[0] = ba[1]; //3
ba[1] = ba[2]; //4
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Buddy[] ba = new Buddy[3]
4. At //4, ba[2] is set to ba[3] but ba[3] is null. Therefore, ba[1] is also null after this line.
Fixed.
1. new Buddy[3] creates an empty array of length 3. No Buddy object is created here and each element of the array points to null.
2. One Buddy object is created at each of the lines //1 and //2.
3. At //3, ba[0] is made to point to the same object as the one pointed to by ba[1]. Therefore, nobody is now pointing to the original Buddy object pointed to by ba[0]. It is therefore eligible for GC now. However, there are two references to the second Buddy object (i.e. ba[0] as well as ba[1] are now pointing to the same Buddy object).
4. At //4, ba[1] is set to ba[2] but ba[2] is null. Therefore, ba[1] is also null after this line.
Therefore, at the end of the initBuddies method, only one Buddy object is eligible for GC.