PriorityQueue throwing class cast exception
PriorityQueue add method throws class cast exception (MyVertex cannot be cast to java.lang.Comparable) on executing.
Some Object of type MyVertex are inserted correctly, and some throws exception, couldn't manage to find the differences between them.
See the attached lines of code in java:
PriorityQueue<Vertex> pq = new PriorityQueue<>();
for (Edge edge : vertex.getEdges()) {
pq.add(edge.getTo());
}
expected: The method pq.add() should not throw an exception.
java priority-queue classcastexception comparable
asked Jan 2 at 14:40
Liran Siman TovLiran Siman Tov
215
|
show 5 more comments
PriorityQueue add method throws class cast exception (MyVertex cannot be cast to java.lang.Comparable) on executing.
Some Object of type MyVertex are inserted correctly, and some throws exception, couldn't manage to find the differences between them.
See the attached lines of code in java:
PriorityQueue<Vertex> pq = new PriorityQueue<>();
for (Edge edge : vertex.getEdges()) {
pq.add(edge.getTo());
}
expected: The method pq.add() should not throw an exception.
java priority-queue classcastexception comparable
asked Jan 2 at 14:40
Liran Siman TovLiran Siman Tov
215
3
is MyVertex implements Comparable?
– wardziniak
Jan 2 at 14:41
3
SeePriorityQueue.add(): "Throws: ClassCastException - if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering" - show us yourMyVertex.compareTo-implementation, seems you've got a bug in there.
– Hulk
Jan 2 at 14:44
Side note: you forgot the diamond innew PriorityQueue<>();- please don't use raw types.
– Hulk
Jan 2 at 14:59
1
@Hulk, First element will be added toPriorityQueueeven if it doesn't implementComparablesince there are no other elements to compare to.
– Ivan
Jan 2 at 15:12
1
@LiranSimanTov Please edit your question to include a Minimal, Complete, and Verifiable example including your classes, which can be compiled and tested by others, which throws an exception when you try to add a new entry to the queue.
– Progman
Jan 2 at 19:24
|
show 5 more comments
PriorityQueue add method throws class cast exception (MyVertex cannot be cast to java.lang.Comparable) on executing.
Some Object of type MyVertex are inserted correctly, and some throws exception, couldn't manage to find the differences between them.
See the attached lines of code in java:
PriorityQueue<Vertex> pq = new PriorityQueue<>();
for (Edge edge : vertex.getEdges()) {
pq.add(edge.getTo());
}
expected: The method pq.add() should not throw an exception.
java priority-queue classcastexception comparable
asked Jan 2 at 14:40
Liran Siman TovLiran Siman Tov
215
PriorityQueue add method throws class cast exception (MyVertex cannot be cast to java.lang.Comparable) on executing.
Some Object of type MyVertex are inserted correctly, and some throws exception, couldn't manage to find the differences between them.
See the attached lines of code in java:
PriorityQueue<Vertex> pq = new PriorityQueue<>();
for (Edge edge : vertex.getEdges()) {
pq.add(edge.getTo());
}
expected: The method pq.add() should not throw an exception.
java priority-queue classcastexception comparable
java priority-queue classcastexception comparable
asked Jan 2 at 14:40
Liran Siman TovLiran Siman Tov
215
asked Jan 2 at 14:40
Liran Siman TovLiran Siman Tov
215
edited Jan 2 at 16:43
Liran Siman Tov
asked Jan 2 at 14:40
Liran Siman TovLiran Siman Tov
215
asked Jan 2 at 14:40
Liran Siman TovLiran Siman Tov
215
asked Jan 2 at 14:40
Liran Siman TovLiran Siman Tov
215
215
3
is MyVertex implements Comparable?
– wardziniak
Jan 2 at 14:41
3
SeePriorityQueue.add(): "Throws: ClassCastException - if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering" - show us yourMyVertex.compareTo-implementation, seems you've got a bug in there.
– Hulk
Jan 2 at 14:44
Side note: you forgot the diamond innew PriorityQueue<>();- please don't use raw types.
– Hulk
Jan 2 at 14:59
1
@Hulk, First element will be added toPriorityQueueeven if it doesn't implementComparablesince there are no other elements to compare to.
– Ivan
Jan 2 at 15:12
1
@LiranSimanTov Please edit your question to include a Minimal, Complete, and Verifiable example including your classes, which can be compiled and tested by others, which throws an exception when you try to add a new entry to the queue.
– Progman
Jan 2 at 19:24
|
show 5 more comments
3
is MyVertex implements Comparable?
– wardziniak
Jan 2 at 14:41
3
SeePriorityQueue.add(): "Throws: ClassCastException - if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering" - show us yourMyVertex.compareTo-implementation, seems you've got a bug in there.
– Hulk
Jan 2 at 14:44
Side note: you forgot the diamond innew PriorityQueue<>();- please don't use raw types.
– Hulk
Jan 2 at 14:59
1
@Hulk, First element will be added toPriorityQueueeven if it doesn't implementComparablesince there are no other elements to compare to.
– Ivan
Jan 2 at 15:12
1
@LiranSimanTov Please edit your question to include a Minimal, Complete, and Verifiable example including your classes, which can be compiled and tested by others, which throws an exception when you try to add a new entry to the queue.
– Progman
Jan 2 at 19:24
3
3
is MyVertex implements Comparable?
– wardziniak
Jan 2 at 14:41
is MyVertex implements Comparable?
– wardziniak
Jan 2 at 14:41
3
3
See
PriorityQueue.add(): "Throws: ClassCastException - if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering" - show us your MyVertex.compareTo-implementation, seems you've got a bug in there.– Hulk
Jan 2 at 14:44
See
PriorityQueue.add(): "Throws: ClassCastException - if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering" - show us your MyVertex.compareTo-implementation, seems you've got a bug in there.– Hulk
Jan 2 at 14:44
Side note: you forgot the diamond in
new PriorityQueue<>(); - please don't use raw types.– Hulk
Jan 2 at 14:59
Side note: you forgot the diamond in
new PriorityQueue<>(); - please don't use raw types.– Hulk
Jan 2 at 14:59
1
1
@Hulk, First element will be added to
PriorityQueue even if it doesn't implement Comparable since there are no other elements to compare to.– Ivan
Jan 2 at 15:12
@Hulk, First element will be added to
PriorityQueue even if it doesn't implement Comparable since there are no other elements to compare to.– Ivan
Jan 2 at 15:12
1
1
@LiranSimanTov Please edit your question to include a Minimal, Complete, and Verifiable example including your classes, which can be compiled and tested by others, which throws an exception when you try to add a new entry to the queue.
– Progman
Jan 2 at 19:24
@LiranSimanTov Please edit your question to include a Minimal, Complete, and Verifiable example including your classes, which can be compiled and tested by others, which throws an exception when you try to add a new entry to the queue.
– Progman
Jan 2 at 19:24
|
show 5 more comments
1 Answer
1
active
oldest
votes
Implement
Comparableinterface and overrideComapareToinsideVertexclass to satisfy the priority queue's ordering.
As the java doc says -
addthrows ClassCastException if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering.
As you say it was working before, its because the add call will not throw the ClassCastException when the priorityQueues's size is 0 (when first element is added). To test that, before the call to the for loop print the size of
vertex.getEdges().size(). If the size appears to be greater than 0, thats when theClassCastExceptionwill be thrown.
When size is not zero a sift-up operation is invoked as the underlying data_structure in the priority queue here is a heap.
The exception that you see is triggered from sift-up, as sift-up internally requires your elements to implement Comparable. And sift-up is called when the priority queue size is not 0, or a subsequent element is added.
Note:
Heap should satisfy the heap property: if P is a parent node of C,
then the key (the value) of P is either greater than or equal to (in
a max heap) or less than or equal to (in a min heap) the key of C.
sift-up: move a node up in the tree, as long as needed; used to
restore heap condition after insertion. Called "sift" because node
moves up the tree until it reaches the correct level, as in a sieve.
Heap_data_structure
answered Jan 3 at 15:00
CodeBusker_JEPCodeBusker_JEP
57027
add a comment |
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Implement
Comparableinterface and overrideComapareToinsideVertexclass to satisfy the priority queue's ordering.
As the java doc says -
addthrows ClassCastException if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering.
As you say it was working before, its because the add call will not throw the ClassCastException when the priorityQueues's size is 0 (when first element is added). To test that, before the call to the for loop print the size of
vertex.getEdges().size(). If the size appears to be greater than 0, thats when theClassCastExceptionwill be thrown.
When size is not zero a sift-up operation is invoked as the underlying data_structure in the priority queue here is a heap.
The exception that you see is triggered from sift-up, as sift-up internally requires your elements to implement Comparable. And sift-up is called when the priority queue size is not 0, or a subsequent element is added.
Note:
Heap should satisfy the heap property: if P is a parent node of C,
then the key (the value) of P is either greater than or equal to (in
a max heap) or less than or equal to (in a min heap) the key of C.
sift-up: move a node up in the tree, as long as needed; used to
restore heap condition after insertion. Called "sift" because node
moves up the tree until it reaches the correct level, as in a sieve.
Heap_data_structure
answered Jan 3 at 15:00
CodeBusker_JEPCodeBusker_JEP
57027
add a comment |
Implement
Comparableinterface and overrideComapareToinsideVertexclass to satisfy the priority queue's ordering.
As the java doc says -
addthrows ClassCastException if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering.
As you say it was working before, its because the add call will not throw the ClassCastException when the priorityQueues's size is 0 (when first element is added). To test that, before the call to the for loop print the size of
vertex.getEdges().size(). If the size appears to be greater than 0, thats when theClassCastExceptionwill be thrown.
When size is not zero a sift-up operation is invoked as the underlying data_structure in the priority queue here is a heap.
The exception that you see is triggered from sift-up, as sift-up internally requires your elements to implement Comparable. And sift-up is called when the priority queue size is not 0, or a subsequent element is added.
Note:
Heap should satisfy the heap property: if P is a parent node of C,
then the key (the value) of P is either greater than or equal to (in
a max heap) or less than or equal to (in a min heap) the key of C.
sift-up: move a node up in the tree, as long as needed; used to
restore heap condition after insertion. Called "sift" because node
moves up the tree until it reaches the correct level, as in a sieve.
Heap_data_structure
answered Jan 3 at 15:00
CodeBusker_JEPCodeBusker_JEP
57027
add a comment |
Implement
Comparableinterface and overrideComapareToinsideVertexclass to satisfy the priority queue's ordering.
As the java doc says -
addthrows ClassCastException if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering.
As you say it was working before, its because the add call will not throw the ClassCastException when the priorityQueues's size is 0 (when first element is added). To test that, before the call to the for loop print the size of
vertex.getEdges().size(). If the size appears to be greater than 0, thats when theClassCastExceptionwill be thrown.
When size is not zero a sift-up operation is invoked as the underlying data_structure in the priority queue here is a heap.
The exception that you see is triggered from sift-up, as sift-up internally requires your elements to implement Comparable. And sift-up is called when the priority queue size is not 0, or a subsequent element is added.
Note:
Heap should satisfy the heap property: if P is a parent node of C,
then the key (the value) of P is either greater than or equal to (in
a max heap) or less than or equal to (in a min heap) the key of C.
sift-up: move a node up in the tree, as long as needed; used to
restore heap condition after insertion. Called "sift" because node
moves up the tree until it reaches the correct level, as in a sieve.
Heap_data_structure
answered Jan 3 at 15:00
CodeBusker_JEPCodeBusker_JEP
57027
Implement
Comparableinterface and overrideComapareToinsideVertexclass to satisfy the priority queue's ordering.
As the java doc says -
addthrows ClassCastException if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering.
As you say it was working before, its because the add call will not throw the ClassCastException when the priorityQueues's size is 0 (when first element is added). To test that, before the call to the for loop print the size of
vertex.getEdges().size(). If the size appears to be greater than 0, thats when theClassCastExceptionwill be thrown.
When size is not zero a sift-up operation is invoked as the underlying data_structure in the priority queue here is a heap.
The exception that you see is triggered from sift-up, as sift-up internally requires your elements to implement Comparable. And sift-up is called when the priority queue size is not 0, or a subsequent element is added.
Note:
Heap should satisfy the heap property: if P is a parent node of C,
then the key (the value) of P is either greater than or equal to (in
a max heap) or less than or equal to (in a min heap) the key of C.
sift-up: move a node up in the tree, as long as needed; used to
restore heap condition after insertion. Called "sift" because node
moves up the tree until it reaches the correct level, as in a sieve.
Heap_data_structure
answered Jan 3 at 15:00
CodeBusker_JEPCodeBusker_JEP
57027
answered Jan 3 at 15:00
CodeBusker_JEPCodeBusker_JEP
57027
answered Jan 3 at 15:00
CodeBusker_JEPCodeBusker_JEP
57027
answered Jan 3 at 15:00
CodeBusker_JEPCodeBusker_JEP
57027
57027
add a comment |
add a comment |
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3
is MyVertex implements Comparable?
– wardziniak
Jan 2 at 14:41
3
See
PriorityQueue.add(): "Throws: ClassCastException - if the specified element cannot be compared with elements currently in this priority queue according to the priority queue's ordering" - show us yourMyVertex.compareTo-implementation, seems you've got a bug in there.– Hulk
Jan 2 at 14:44
Side note: you forgot the diamond in
new PriorityQueue<>();- please don't use raw types.– Hulk
Jan 2 at 14:59
1
@Hulk, First element will be added to
PriorityQueueeven if it doesn't implementComparablesince there are no other elements to compare to.– Ivan
Jan 2 at 15:12
1
@LiranSimanTov Please edit your question to include a Minimal, Complete, and Verifiable example including your classes, which can be compiled and tested by others, which throws an exception when you try to add a new entry to the queue.
– Progman
Jan 2 at 19:24