CODEWITHSUNDEEP
javalinked-list
mkuk
mkuk

Reputation: 300

LinkedList temp.next and temp?

So I was practicing some linked list problems and I keep getting mixed up with let say we do // this is a head only singly linked list

// what is the difference between 

ListNode temp = head;
while( temp != null ) {
    temp = temp.next ; 
} 

while( temp.next != null ) {
    temp = temp.next ; 
}

again what is the difference between the two ? If you can please explain to me this it would be greatly appreciated.

Upvotes: 1

Views: 2701

Answers (4)

Matt Lacey
Matt Lacey

Reputation: 8255

The first example terminates when temp == null, meaning that temp will have the value null after the loop and not be of much use to you, though for processing the items in the list this is a perfectly valid approach.

The second example will stop when temp.next == null but temp itself actually has a value, in this case it will be a reference to the tail of the list, which is far more useful if you want to add something else on to the list as well.

As some others have indicated, the second will cause a null dereference exception if temp is null, but this would only be an issue if temp was null before processing the loop, so this can be averted with a conditional.

Upvotes: 2

Ishant Goyal
Ishant Goyal

Reputation: 1

The second loop will generate a nullPointerException while executing the condition so it is not an efficient way.

Upvotes: 0

LeleDumbo
LeleDumbo

Reputation: 9340

The second has a potential of getting NullPointerException if temp itself is null when checking the while condition for the first time. The first is safe from such exception.

The second would end up in the last element in the linked list, while the first would end up in null.

Upvotes: 0

hackartist
hackartist

Reputation: 5264

the first will stop one link later than the second one so if you want to process every node then use the first.

Upvotes: 1

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