jsimple.util

Class Set<E>

java.lang.Object

jsimple.lang.Iterable<E>

jsimple.util.Collection<E>

jsimple.util.Set<E>

All Implemented Interfaces:

java.lang.Iterable<E>

Direct Known Subclasses:

HashSet

public abstract class Set<E>
extends Collection<E>

An AbstractSet is an abstract implementation of the Set interface. This implementation does not support adding. A subclass must implement the abstract methods iterator() and size().

Since:

1.2

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Set() Constructs a new instance of this AbstractSet.

Method Summary

Modifier and Type	Method and Description
boolean	equals(java.lang.Object object) By default, equals isn't supported for sets or other collections, though subclasses can choose to override this behavior if they want.
int	hashCode() Returns the hash code for this set.
boolean	removeAll(Collection<E> collection) Removes all occurrences in this collection which are contained in the specified collection.

Methods inherited from class jsimple.util.Collection

add, addAll, clear, contains, containsAll, isEmpty, iterator, remove, retainAll, size, toArray, toArray, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

Set

protected Set()

Constructs a new instance of this AbstractSet.

Method Detail

equals

public boolean equals(java.lang.Object object)

By default, equals isn't supported for sets or other collections, though subclasses can choose to override this behavior if they want. Instead developers should call some other, more specific, method, checking for the exact kind of equality they want.

As background: This behavior differs from the standard java.util.AbstractSet.equals method, where two sets are considered equal if the have the same number of elements and those elements are equals, according to equals. That's so-called deep equality. Whereas C#, on the other hand, just does reference equality by default for sets, saying two are equal if their references are equals.

There are two main reasons we differ from standard Java and don't support equals here for collection classes:

(a) The desired semantics are ambiguous (deep, shallow, or reference equality? set type matter?). Different semantics are appropriate in different cases. (b) It's hard to implement the Java semantics and support generics, with covariance, properly and have it work with Java to C#/Swift translation. Limited C# and Swift support for covariance, especially when casting from an Object, makes it all the harder. So best to just avoid all those issues & make the developer do explicitly what they want, calling some other method.

Overrides:

equals in class java.lang.Object

Parameters:

object - the object to compare to this object.

Returns:

true if the specified object is equal to this set, false otherwise; though by default this method throws an exception and developers generally shouldn't use equals on collections

hashCode

public int hashCode()

Returns the hash code for this set. Two set which are equal must return the same value.

The default implementation calculates the hash code by adding each element's hash code.

Overrides:

hashCode in class java.lang.Object

Returns:

the hash code of this set.

See Also:

equals(java.lang.Object)

removeAll

public boolean removeAll(Collection<E> collection)

Removes all occurrences in this collection which are contained in the specified collection.

Overrides:

removeAll in class Collection<E>

Parameters:

collection - the collection of objects to remove.

Returns:

true if this collection was modified, false otherwise.