/usr/share/why/java_api/java/util/Collection.java is in why 2.34-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 | /*
* @(#)Collection.java 1.39 03/01/17
*
* Copyright 2003 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util;
/**
* The root interface in the <i>collection hierarchy</i>. A collection
* represents a group of objects, known as its <i>elements</i>. Some
* collections allow duplicate elements and others do not. Some are ordered
* and others unordered. The SDK does not provide any <i>direct</i>
* implementations of this interface: it provides implementations of more
* specific subinterfaces like <tt>Set</tt> and <tt>List</tt>. This interface
* is typically used to pass collections around and manipulate them where
* maximum generality is desired.
*
* <p><i>Bags</i> or <i>multisets</i> (unordered collections that may contain
* duplicate elements) should implement this interface directly.
*
* <p>All general-purpose <tt>Collection</tt> implementation classes (which
* typically implement <tt>Collection</tt> indirectly through one of its
* subinterfaces) should provide two "standard" constructors: a void (no
* arguments) constructor, which creates an empty collection, and a
* constructor with a single argument of type <tt>Collection</tt>, which
* creates a new collection with the same elements as its argument. In
* effect, the latter constructor allows the user to copy any collection,
* producing an equivalent collection of the desired implementation type.
* There is no way to enforce this convention (as interfaces cannot contain
* constructors) but all of the general-purpose <tt>Collection</tt>
* implementations in the Java platform libraries comply.
*
* <p>The "destructive" methods contained in this interface, that is, the
* methods that modify the collection on which they operate, are specified to
* throw <tt>UnsupportedOperationException</tt> if this collection does not
* support the operation. If this is the case, these methods may, but are not
* required to, throw an <tt>UnsupportedOperationException</tt> if the
* invocation would have no effect on the collection. For example, invoking
* the {@link #addAll(Collection)} method on an unmodifiable collection may,
* but is not required to, throw the exception if the collection to be added
* is empty.
*
* <p>Some collection implementations have restrictions on the elements that
* they may contain. For example, some implementations prohibit null elements,
* and some have restrictions on the types of their elements. Attempting to
* add an ineligible element throws an unchecked exception, typically
* <tt>NullPointerException</tt> or <tt>ClassCastException</tt>. Attempting
* to query the presence of an ineligible element may throw an exception,
* or it may simply return false; some implementations will exhibit the former
* behavior and some will exhibit the latter. More generally, attempting an
* operation on an ineligible element whose completion would not result in
* the insertion of an ineligible element into the collection may throw an
* exception or it may succeed, at the option of the implementation.
* Such exceptions are marked as "optional" in the specification for this
* interface.
*
* <p>This interface is a member of the
* <a href="{@docRoot}/../guide/collections/index.html">
* Java Collections Framework</a>.
*
* @author Josh Bloch
* @version 1.40, 01/23/03
* @see Set
* @see List
* @see Map
* @see SortedSet
* @see SortedMap
* @see HashSet
* @see TreeSet
* @see ArrayList
* @see LinkedList
* @see Vector
* @see Collections
* @see Arrays
* @see AbstractCollection
* @since 1.2
*/
public interface Collection {
// Query Operations
/**
* Returns the number of elements in this collection. If this collection
* contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
* <tt>Integer.MAX_VALUE</tt>.
*
* @return the number of elements in this collection
*/
int size();
/**
* Returns <tt>true</tt> if this collection contains no elements.
*
* @return <tt>true</tt> if this collection contains no elements
*/
boolean isEmpty();
/**
* Returns <tt>true</tt> if this collection contains the specified
* element. More formally, returns <tt>true</tt> if and only if this
* collection contains at least one element <tt>e</tt> such that
* <tt>(o==null ? e==null : o.equals(e))</tt>.
*
* @param o element whose presence in this collection is to be tested.
* @return <tt>true</tt> if this collection contains the specified
* element
* @throws ClassCastException if the type of the specified element
* is incompatible with this collection (optional).
* @throws NullPointerException if the specified element is null and this
* collection does not support null elements (optional).
*/
boolean contains(Object o);
/**
* Returns an iterator over the elements in this collection. There are no
* guarantees concerning the order in which the elements are returned
* (unless this collection is an instance of some class that provides a
* guarantee).
*
* @return an <tt>Iterator</tt> over the elements in this collection
*/
Iterator iterator();
/**
* Returns an array containing all of the elements in this collection. If
* the collection makes any guarantees as to what order its elements are
* returned by its iterator, this method must return the elements in the
* same order.<p>
*
* The returned array will be "safe" in that no references to it are
* maintained by this collection. (In other words, this method must
* allocate a new array even if this collection is backed by an array).
* The caller is thus free to modify the returned array.<p>
*
* This method acts as bridge between array-based and collection-based
* APIs.
*
* @return an array containing all of the elements in this collection
*/
Object[] toArray();
/**
* Returns an array containing all of the elements in this collection;
* the runtime type of the returned array is that of the specified array.
* If the collection fits in the specified array, it is returned therein.
* Otherwise, a new array is allocated with the runtime type of the
* specified array and the size of this collection.<p>
*
* If this collection fits in the specified array with room to spare
* (i.e., the array has more elements than this collection), the element
* in the array immediately following the end of the collection is set to
* <tt>null</tt>. This is useful in determining the length of this
* collection <i>only</i> if the caller knows that this collection does
* not contain any <tt>null</tt> elements.)<p>
*
* If this collection makes any guarantees as to what order its elements
* are returned by its iterator, this method must return the elements in
* the same order.<p>
*
* Like the <tt>toArray</tt> method, this method acts as bridge between
* array-based and collection-based APIs. Further, this method allows
* precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs<p>
*
* Suppose <tt>l</tt> is a <tt>List</tt> known to contain only strings.
* The following code can be used to dump the list into a newly allocated
* array of <tt>String</tt>:
*
* <pre>
* String[] x = (String[]) v.toArray(new String[0]);
* </pre><p>
*
* Note that <tt>toArray(new Object[0])</tt> is identical in function to
* <tt>toArray()</tt>.
*
* @param a the array into which the elements of this collection are to be
* stored, if it is big enough; otherwise, a new array of the same
* runtime type is allocated for this purpose.
* @return an array containing the elements of this collection
*
* @throws ArrayStoreException the runtime type of the specified array is
* not a supertype of the runtime type of every element in this
* collection.
* @throws NullPointerException if the specified array is <tt>null</tt>.
*/
Object[] toArray(Object a[]);
// Modification Operations
/**
* Ensures that this collection contains the specified element (optional
* operation). Returns <tt>true</tt> if this collection changed as a
* result of the call. (Returns <tt>false</tt> if this collection does
* not permit duplicates and already contains the specified element.)<p>
*
* Collections that support this operation may place limitations on what
* elements may be added to this collection. In particular, some
* collections will refuse to add <tt>null</tt> elements, and others will
* impose restrictions on the type of elements that may be added.
* Collection classes should clearly specify in their documentation any
* restrictions on what elements may be added.<p>
*
* If a collection refuses to add a particular element for any reason
* other than that it already contains the element, it <i>must</i> throw
* an exception (rather than returning <tt>false</tt>). This preserves
* the invariant that a collection always contains the specified element
* after this call returns.
*
* @param o element whose presence in this collection is to be ensured.
* @return <tt>true</tt> if this collection changed as a result of the
* call
*
* @throws UnsupportedOperationException <tt>add</tt> is not supported by
* this collection.
* @throws ClassCastException class of the specified element prevents it
* from being added to this collection.
* @throws NullPointerException if the specified element is null and this
* collection does not support null elements.
* @throws IllegalArgumentException some aspect of this element prevents
* it from being added to this collection.
*/
boolean add(Object o);
/**
* Removes a single instance of the specified element from this
* collection, if it is present (optional operation). More formally,
* removes an element <tt>e</tt> such that <tt>(o==null ? e==null :
* o.equals(e))</tt>, if this collection contains one or more such
* elements. Returns true if this collection contained the specified
* element (or equivalently, if this collection changed as a result of the
* call).
*
* @param o element to be removed from this collection, if present.
* @return <tt>true</tt> if this collection changed as a result of the
* call
*
* @throws ClassCastException if the type of the specified element
* is incompatible with this collection (optional).
* @throws NullPointerException if the specified element is null and this
* collection does not support null elements (optional).
* @throws UnsupportedOperationException remove is not supported by this
* collection.
*/
boolean remove(Object o);
// Bulk Operations
/**
* Returns <tt>true</tt> if this collection contains all of the elements
* in the specified collection.
*
* @param c collection to be checked for containment in this collection.
* @return <tt>true</tt> if this collection contains all of the elements
* in the specified collection
* @throws ClassCastException if the types of one or more elements
* in the specified collection are incompatible with this
* collection (optional).
* @throws NullPointerException if the specified collection contains one
* or more null elements and this collection does not support null
* elements (optional).
* @throws NullPointerException if the specified collection is
* <tt>null</tt>.
* @see #contains(Object)
*/
boolean containsAll(Collection c);
/**
* Adds all of the elements in the specified collection to this collection
* (optional operation). The behavior of this operation is undefined if
* the specified collection is modified while the operation is in progress.
* (This implies that the behavior of this call is undefined if the
* specified collection is this collection, and this collection is
* nonempty.)
*
* @param c elements to be inserted into this collection.
* @return <tt>true</tt> if this collection changed as a result of the
* call
*
* @throws UnsupportedOperationException if this collection does not
* support the <tt>addAll</tt> method.
* @throws ClassCastException if the class of an element of the specified
* collection prevents it from being added to this collection.
* @throws NullPointerException if the specified collection contains one
* or more null elements and this collection does not support null
* elements, or if the specified collection is <tt>null</tt>.
* @throws IllegalArgumentException some aspect of an element of the
* specified collection prevents it from being added to this
* collection.
* @see #add(Object)
*/
boolean addAll(Collection c);
/**
*
* Removes all this collection's elements that are also contained in the
* specified collection (optional operation). After this call returns,
* this collection will contain no elements in common with the specified
* collection.
*
* @param c elements to be removed from this collection.
* @return <tt>true</tt> if this collection changed as a result of the
* call
*
* @throws UnsupportedOperationException if the <tt>removeAll</tt> method
* is not supported by this collection.
* @throws ClassCastException if the types of one or more elements
* in this collection are incompatible with the specified
* collection (optional).
* @throws NullPointerException if this collection contains one or more
* null elements and the specified collection does not support
* null elements (optional).
* @throws NullPointerException if the specified collection is
* <tt>null</tt>.
* @see #remove(Object)
* @see #contains(Object)
*/
boolean removeAll(Collection c);
/**
* Retains only the elements in this collection that are contained in the
* specified collection (optional operation). In other words, removes from
* this collection all of its elements that are not contained in the
* specified collection.
*
* @param c elements to be retained in this collection.
* @return <tt>true</tt> if this collection changed as a result of the
* call
*
* @throws UnsupportedOperationException if the <tt>retainAll</tt> method
* is not supported by this Collection.
* @throws ClassCastException if the types of one or more elements
* in this collection are incompatible with the specified
* collection (optional).
* @throws NullPointerException if this collection contains one or more
* null elements and the specified collection does not support null
* elements (optional).
* @throws NullPointerException if the specified collection is
* <tt>null</tt>.
* @see #remove(Object)
* @see #contains(Object)
*/
boolean retainAll(Collection c);
/**
* Removes all of the elements from this collection (optional operation).
* This collection will be empty after this method returns unless it
* throws an exception.
*
* @throws UnsupportedOperationException if the <tt>clear</tt> method is
* not supported by this collection.
*/
void clear();
// Comparison and hashing
/**
* Compares the specified object with this collection for equality. <p>
*
* While the <tt>Collection</tt> interface adds no stipulations to the
* general contract for the <tt>Object.equals</tt>, programmers who
* implement the <tt>Collection</tt> interface "directly" (in other words,
* create a class that is a <tt>Collection</tt> but is not a <tt>Set</tt>
* or a <tt>List</tt>) must exercise care if they choose to override the
* <tt>Object.equals</tt>. It is not necessary to do so, and the simplest
* course of action is to rely on <tt>Object</tt>'s implementation, but
* the implementer may wish to implement a "value comparison" in place of
* the default "reference comparison." (The <tt>List</tt> and
* <tt>Set</tt> interfaces mandate such value comparisons.)<p>
*
* The general contract for the <tt>Object.equals</tt> method states that
* equals must be symmetric (in other words, <tt>a.equals(b)</tt> if and
* only if <tt>b.equals(a)</tt>). The contracts for <tt>List.equals</tt>
* and <tt>Set.equals</tt> state that lists are only equal to other lists,
* and sets to other sets. Thus, a custom <tt>equals</tt> method for a
* collection class that implements neither the <tt>List</tt> nor
* <tt>Set</tt> interface must return <tt>false</tt> when this collection
* is compared to any list or set. (By the same logic, it is not possible
* to write a class that correctly implements both the <tt>Set</tt> and
* <tt>List</tt> interfaces.)
*
* @param o Object to be compared for equality with this collection.
* @return <tt>true</tt> if the specified object is equal to this
* collection
*
* @see Object#equals(Object)
* @see Set#equals(Object)
* @see List#equals(Object)
*/
boolean equals(Object o);
/**
* Returns the hash code value for this collection. While the
* <tt>Collection</tt> interface adds no stipulations to the general
* contract for the <tt>Object.hashCode</tt> method, programmers should
* take note that any class that overrides the <tt>Object.equals</tt>
* method must also override the <tt>Object.hashCode</tt> method in order
* to satisfy the general contract for the <tt>Object.hashCode</tt>method.
* In particular, <tt>c1.equals(c2)</tt> implies that
* <tt>c1.hashCode()==c2.hashCode()</tt>.
*
* @return the hash code value for this collection
*
* @see Object#hashCode()
* @see Object#equals(Object)
*/
int hashCode();
}
|