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In C this concept becomes beautifully clear with pointers but im having trouble understanding what exactly is going on here in java.

Can someone please explain to me how come when i traverse the list in removeNode(), it doesnt change any thing on the original object BUT when i do front.next = front.next.next it actually changes the object. Its driving me crazy cause in C i can just use pointers to edit w/e i want. What exactly is going on here with the references?

Note: I know this code doesnt handle edge cases. like null nodes, etc...

public class LLnode
 int value;
 LLnode next;

 public LLnode(int x)
 this.value = x;
 this.next = NULL;
 


/*
 * This fn removes the node with the specified value n from the linked list
 */
public void removeNode(LLnode head, int n)
 LLnode front = head;
 while (front.next.value != n)
 front = front.next; //why DOESN'T this physically change the LL?
 
 front.next = front.next.next; //why DOES this physically change the LL ?

public static void main(String[] args)
 //node creation
 LLnode a = new LLnode(10);
 LLnode b = new LLnode(20);
 LLnode c = new LLnode(30);
 LLnode d = new LLnode(40);

 //assignments
 c.next = d;
 b.next = c;
 a.next = b;

 removeNode(a,30);

Thanks.

java linked-list

share|improve this question

asked Mar 28 at 20:07

shockwave88shockwave88

822 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  front = front.next; - that's just changing a local variable front so that the value is the current value of value.next. Compare that with front.next = front.next.next; which modifies the object referred to by the current value of front. You might find this question useful: stackoverflow.com/questions/32010172/…
  
  – Jon Skeet
  Mar 28 at 20:10
  

  
  
  
  

add a comment
 | 

0

In C this concept becomes beautifully clear with pointers but im having trouble understanding what exactly is going on here in java.

Can someone please explain to me how come when i traverse the list in removeNode(), it doesnt change any thing on the original object BUT when i do front.next = front.next.next it actually changes the object. Its driving me crazy cause in C i can just use pointers to edit w/e i want. What exactly is going on here with the references?

Note: I know this code doesnt handle edge cases. like null nodes, etc...

public class LLnode
 int value;
 LLnode next;

 public LLnode(int x)
 this.value = x;
 this.next = NULL;
 


/*
 * This fn removes the node with the specified value n from the linked list
 */
public void removeNode(LLnode head, int n)
 LLnode front = head;
 while (front.next.value != n)
 front = front.next; //why DOESN'T this physically change the LL?
 
 front.next = front.next.next; //why DOES this physically change the LL ?

public static void main(String[] args)
 //node creation
 LLnode a = new LLnode(10);
 LLnode b = new LLnode(20);
 LLnode c = new LLnode(30);
 LLnode d = new LLnode(40);

 //assignments
 c.next = d;
 b.next = c;
 a.next = b;

 removeNode(a,30);

Thanks.

java linked-list

share|improve this question

asked Mar 28 at 20:07

shockwave88shockwave88

822 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  front = front.next; - that's just changing a local variable front so that the value is the current value of value.next. Compare that with front.next = front.next.next; which modifies the object referred to by the current value of front. You might find this question useful: stackoverflow.com/questions/32010172/…
  
  – Jon Skeet
  Mar 28 at 20:10
  

  
  
  
  

add a comment
 | 

In C this concept becomes beautifully clear with pointers but im having trouble understanding what exactly is going on here in java.

Can someone please explain to me how come when i traverse the list in removeNode(), it doesnt change any thing on the original object BUT when i do front.next = front.next.next it actually changes the object. Its driving me crazy cause in C i can just use pointers to edit w/e i want. What exactly is going on here with the references?

Note: I know this code doesnt handle edge cases. like null nodes, etc...

public class LLnode
 int value;
 LLnode next;

 public LLnode(int x)
 this.value = x;
 this.next = NULL;
 


/*
 * This fn removes the node with the specified value n from the linked list
 */
public void removeNode(LLnode head, int n)
 LLnode front = head;
 while (front.next.value != n)
 front = front.next; //why DOESN'T this physically change the LL?
 
 front.next = front.next.next; //why DOES this physically change the LL ?

public static void main(String[] args)
 //node creation
 LLnode a = new LLnode(10);
 LLnode b = new LLnode(20);
 LLnode c = new LLnode(30);
 LLnode d = new LLnode(40);

 //assignments
 c.next = d;
 b.next = c;
 a.next = b;

 removeNode(a,30);

Thanks.

java linked-list

share|improve this question

asked Mar 28 at 20:07

shockwave88shockwave88

822 bronze badges

public class LLnode
 int value;
 LLnode next;

 public LLnode(int x)
 this.value = x;
 this.next = NULL;
 


/*
 * This fn removes the node with the specified value n from the linked list
 */
public void removeNode(LLnode head, int n)
 LLnode front = head;
 while (front.next.value != n)
 front = front.next; //why DOESN'T this physically change the LL?
 
 front.next = front.next.next; //why DOES this physically change the LL ?

public static void main(String[] args)
 //node creation
 LLnode a = new LLnode(10);
 LLnode b = new LLnode(20);
 LLnode c = new LLnode(30);
 LLnode d = new LLnode(40);

 //assignments
 c.next = d;
 b.next = c;
 a.next = b;

 removeNode(a,30);

share|improve this question

asked Mar 28 at 20:07

shockwave88shockwave88

822 bronze badges

share|improve this question

asked Mar 28 at 20:07

shockwave88shockwave88

822 bronze badges

asked Mar 28 at 20:07

shockwave88shockwave88

822 bronze badges

asked Mar 28 at 20:07

shockwave88shockwave88

822 bronze badges

1 Answer
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Java is pass-by-value. front = head copies the reference value from head into front. Because of that front = front.next has no effect on the head. In the loop front is created only to point into current element, it's not used to maintain the list.

However front.next = front.next.next changes the next field in an object referenced by front. There is no reference copy for next field here, like previously front was a copy of head.

share|improve this answer

answered Mar 28 at 20:21

Karol DowbeckiKarol Dowbecki

30.3k99 gold badges4343 silver badges6363 bronze badges

add a comment
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0

Java is pass-by-value. front = head copies the reference value from head into front. Because of that front = front.next has no effect on the head. In the loop front is created only to point into current element, it's not used to maintain the list.

However front.next = front.next.next changes the next field in an object referenced by front. There is no reference copy for next field here, like previously front was a copy of head.

share|improve this answer

answered Mar 28 at 20:21

Karol DowbeckiKarol Dowbecki

30.3k99 gold badges4343 silver badges6363 bronze badges

add a comment
 | 

0

Java is pass-by-value. front = head copies the reference value from head into front. Because of that front = front.next has no effect on the head. In the loop front is created only to point into current element, it's not used to maintain the list.

However front.next = front.next.next changes the next field in an object referenced by front. There is no reference copy for next field here, like previously front was a copy of head.

share|improve this answer

answered Mar 28 at 20:21

Karol DowbeckiKarol Dowbecki

30.3k99 gold badges4343 silver badges6363 bronze badges

add a comment
 | 

Java is pass-by-value. front = head copies the reference value from head into front. Because of that front = front.next has no effect on the head. In the loop front is created only to point into current element, it's not used to maintain the list.

However front.next = front.next.next changes the next field in an object referenced by front. There is no reference copy for next field here, like previously front was a copy of head.

share|improve this answer

answered Mar 28 at 20:21

Karol DowbeckiKarol Dowbecki

30.3k99 gold badges4343 silver badges6363 bronze badges

share|improve this answer

answered Mar 28 at 20:21

Karol DowbeckiKarol Dowbecki

30.3k99 gold badges4343 silver badges6363 bronze badges

answered Mar 28 at 20:21

Karol DowbeckiKarol Dowbecki

30.3k99 gold badges4343 silver badges6363 bronze badges

answered Mar 28 at 20:21

Karol DowbeckiKarol Dowbecki

30.3k99 gold badges4343 silver badges6363 bronze badges