collections

问题 Is there any rational for Option not being Traversable ? In Scala 2.9, Seq(Set(1,3,2),Seq(4),Option(5)).flatten doesn't compile and simply having it to implement the Traversable trait seams rational to me. If it's not the case, there must be something I don't see that don't allow it. What is it? PS: While trying to understand, I achieved awful things that compile, like: scala> Seq(Set(1,3,2),Seq(4),Map("one"->1, 2->"two")).flatten res1: Seq[Any] = List(1, 3, 2, 4, (one,1), (2,two)) PS2: I

问题 Is there any rational for Option not being Traversable ? In Scala 2.9, Seq(Set(1,3,2),Seq(4),Option(5)).flatten doesn't compile and simply having it to implement the Traversable trait seams rational to me. If it's not the case, there must be something I don't see that don't allow it. What is it? PS: While trying to understand, I achieved awful things that compile, like: scala> Seq(Set(1,3,2),Seq(4),Map("one"->1, 2->"two")).flatten res1: Seq[Any] = List(1, 3, 2, 4, (one,1), (2,two)) PS2: I

问题 I thought I understood the difference between ArrayList and LinkedList theoretically pretty well. However, its the first time, I put it to a little test, and the tests came out, well different to my expectations. Expectations : Arraylist will be slower than LinkedList when inserting at the beginning, since it has to "shift" the elements, for linkedlist, its just updating 2 references. Reality : came out to be same on most iterations. For a select few iterations, it was slower. Arraylist will

问题 I have 3 form types in symfony2 FaultType which is the parent of all next collections <?php namespace My\FaultBundle\Form; use Symfony\Component\Form\AbstractType; use Symfony\Component\Form\FormBuilder; class FaultType extends AbstractType { public function buildForm(FormBuilder $builder, array $options) { $builder ->add('title') ->add('steps', 'collection', array( 'type' => new StepType(), 'allow_add' => true, 'prototype' => true, 'by_reference' => false, )) ->add('created') ->add('updated'

问题 I have 3 form types in symfony2 FaultType which is the parent of all next collections <?php namespace My\FaultBundle\Form; use Symfony\Component\Form\AbstractType; use Symfony\Component\Form\FormBuilder; class FaultType extends AbstractType { public function buildForm(FormBuilder $builder, array $options) { $builder ->add('title') ->add('steps', 'collection', array( 'type' => new StepType(), 'allow_add' => true, 'prototype' => true, 'by_reference' => false, )) ->add('created') ->add('updated'

问题 I have 3 form types in symfony2 FaultType which is the parent of all next collections <?php namespace My\FaultBundle\Form; use Symfony\Component\Form\AbstractType; use Symfony\Component\Form\FormBuilder; class FaultType extends AbstractType { public function buildForm(FormBuilder $builder, array $options) { $builder ->add('title') ->add('steps', 'collection', array( 'type' => new StepType(), 'allow_add' => true, 'prototype' => true, 'by_reference' => false, )) ->add('created') ->add('updated'

问题 More specifically I want an interface to compare objects which can be only compared for equality [e.g. complex numbers] but don't have total order on them. It should have [Note that it only returns a boolean yes/no] boolean Equals(T object1, T object2); and a hashcode function. So that when I distribute them into buckets using objects say to collect "equal" objects, 2 "equal" objects don't end up in two different buckets. int getHashCode(T object); Does Java have one? I searched and couldn't

问题 More specifically I want an interface to compare objects which can be only compared for equality [e.g. complex numbers] but don't have total order on them. It should have [Note that it only returns a boolean yes/no] boolean Equals(T object1, T object2); and a hashcode function. So that when I distribute them into buckets using objects say to collect "equal" objects, 2 "equal" objects don't end up in two different buckets. int getHashCode(T object); Does Java have one? I searched and couldn't

问题 More specifically I want an interface to compare objects which can be only compared for equality [e.g. complex numbers] but don't have total order on them. It should have [Note that it only returns a boolean yes/no] boolean Equals(T object1, T object2); and a hashcode function. So that when I distribute them into buckets using objects say to collect "equal" objects, 2 "equal" objects don't end up in two different buckets. int getHashCode(T object); Does Java have one? I searched and couldn't

问题 More specifically I want an interface to compare objects which can be only compared for equality [e.g. complex numbers] but don't have total order on them. It should have [Note that it only returns a boolean yes/no] boolean Equals(T object1, T object2); and a hashcode function. So that when I distribute them into buckets using objects say to collect "equal" objects, 2 "equal" objects don't end up in two different buckets. int getHashCode(T object); Does Java have one? I searched and couldn't