Source for java.util.Set

   1: /* Set.java -- A collection that prohibits duplicates
   2:    Copyright (C) 1998, 2001, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package java.util;
  40: 
  41: /**
  42:  * A collection that contains no duplicates. In other words, for two set
  43:  * elements e1 and e2, <code>e1.equals(e2)</code> returns false. There
  44:  * are additional stipulations on <code>add</code>, <code>equals</code>
  45:  * and <code>hashCode</code>, as well as the requirements that constructors
  46:  * do not permit duplicate elements. The Set interface is incompatible with
  47:  * List; you cannot implement both simultaneously.
  48:  * <p>
  49:  *
  50:  * Note: Be careful about using mutable objects in sets.  In particular,
  51:  * if a mutable object changes to become equal to another set element, you
  52:  * have violated the contract.  As a special case of this, a Set is not
  53:  * allowed to be an element of itself, without risking undefined behavior.
  54:  *
  55:  * @author Original author unknown
  56:  * @author Eric Blake (ebb9@email.byu.edu)
  57:  * @see Collection
  58:  * @see List
  59:  * @see SortedSet
  60:  * @see HashSet
  61:  * @see TreeSet
  62:  * @see LinkedHashSet
  63:  * @see AbstractSet
  64:  * @see Collections#singleton(Object)
  65:  * @see Collections#EMPTY_SET
  66:  * @since 1.2
  67:  * @status updated to 1.4
  68:  */
  69: public interface Set extends Collection
  70: {
  71:   /**
  72:    * Adds the specified element to the set if it is not already present
  73:    * (optional operation). In particular, the comparison algorithm is
  74:    * <code>o == null ? e == null : o.equals(e)</code>. Sets need not permit
  75:    * all values, and may document what exceptions will be thrown if
  76:    * a value is not permitted.
  77:    *
  78:    * @param o the object to add
  79:    * @return true if the object was not previously in the set
  80:    * @throws UnsupportedOperationException if this operation is not allowed
  81:    * @throws ClassCastException if the class of o prevents it from being added
  82:    * @throws IllegalArgumentException if some aspect of o prevents it from
  83:    *         being added
  84:    * @throws NullPointerException if null is not permitted in this set
  85:    */
  86:   boolean add(Object o);
  87: 
  88:   /**
  89:    * Adds all of the elements of the given collection to this set (optional
  90:    * operation). If the argument is also a Set, this returns the mathematical
  91:    * <i>union</i> of the two. The behavior is unspecified if the set is
  92:    * modified while this is taking place.
  93:    *
  94:    * @param c the collection to add
  95:    * @return true if the set changed as a result
  96:    * @throws UnsupportedOperationException if this operation is not allowed
  97:    * @throws ClassCastException if the class of an element prevents it from
  98:    *         being added
  99:    * @throws IllegalArgumentException if something about an element prevents
 100:    *         it from being added
 101:    * @throws NullPointerException if null is not permitted in this set, or
 102:    *         if the argument c is null
 103:    * @see #add(Object)
 104:    */
 105:   boolean addAll(Collection c);
 106: 
 107:   /**
 108:    * Removes all elements from this set (optional operation). This set will
 109:    * be empty afterwords, unless an exception occurs.
 110:    *
 111:    * @throws UnsupportedOperationException if this operation is not allowed
 112:    */
 113:   void clear();
 114: 
 115:   /**
 116:    * Returns true if the set contains the specified element. In other words,
 117:    * this looks for <code>o == null ? e == null : o.equals(e)</code>.
 118:    *
 119:    * @param o the object to look for
 120:    * @return true if it is found in the set
 121:    * @throws ClassCastException if the type of o is not a valid type
 122:    *         for this set.
 123:    * @throws NullPointerException if o is null and this set doesn't
 124:    *         support null values.
 125:    */
 126:   boolean contains(Object o);
 127: 
 128:   /**
 129:    * Returns true if this set contains all elements in the specified
 130:    * collection. If the argument is also a set, this is the <i>subset</i>
 131:    * relationship.
 132:    *
 133:    * @param c the collection to check membership in
 134:    * @return true if all elements in this set are in c
 135:    * @throws NullPointerException if c is null
 136:    * @throws ClassCastException if the type of any element in c is not
 137:    *         a valid type for this set.
 138:    * @throws NullPointerException if some element of c is null and this
 139:    *         set doesn't support null values.
 140:    * @see #contains(Object)
 141:    */
 142:   boolean containsAll(Collection c);
 143: 
 144:   /**
 145:    * Compares the specified object to this for equality. For sets, the object
 146:    * must be a set, the two must have the same size, and every element in
 147:    * one must be in the other.
 148:    *
 149:    * @param o the object to compare to
 150:    * @return true if it is an equal set
 151:    */
 152:   boolean equals(Object o);
 153: 
 154:   /**
 155:    * Returns the hash code for this set. In order to satisfy the contract of
 156:    * equals, this is the sum of the hashcode of all elements in the set.
 157:    *
 158:    * @return the sum of the hashcodes of all set elements
 159:    * @see #equals(Object)
 160:    */
 161:   int hashCode();
 162: 
 163:   /**
 164:    * Returns true if the set contains no elements.
 165:    *
 166:    * @return true if the set is empty
 167:    */
 168:   boolean isEmpty();
 169: 
 170:   /**
 171:    * Returns an iterator over the set.  The iterator has no specific order,
 172:    * unless further specified.
 173:    *
 174:    * @return a set iterator
 175:    */
 176:   Iterator iterator();
 177: 
 178:   /**
 179:    * Removes the specified element from this set (optional operation). If
 180:    * an element e exists, <code>o == null ? e == null : o.equals(e)</code>,
 181:    * it is removed from the set.
 182:    *
 183:    * @param o the object to remove
 184:    * @return true if the set changed (an object was removed)
 185:    * @throws UnsupportedOperationException if this operation is not allowed
 186:    * @throws ClassCastException if the type of o is not a valid type
 187:    *         for this set.
 188:    * @throws NullPointerException if o is null and this set doesn't allow
 189:    *         the removal of a null value.
 190:    */
 191:   boolean remove(Object o);
 192: 
 193:   /**
 194:    * Removes from this set all elements contained in the specified collection
 195:    * (optional operation). If the argument is a set, this returns the
 196:    * <i>asymmetric set difference</i> of the two sets.
 197:    *
 198:    * @param c the collection to remove from this set
 199:    * @return true if this set changed as a result
 200:    * @throws UnsupportedOperationException if this operation is not allowed
 201:    * @throws NullPointerException if c is null
 202:    * @throws ClassCastException if the type of any element in c is not
 203:    *         a valid type for this set.
 204:    * @throws NullPointerException if some element of c is null and this
 205:    *         set doesn't support removing null values.
 206:    * @see #remove(Object)
 207:    */
 208:   boolean removeAll(Collection c);
 209: 
 210:   /**
 211:    * Retains only the elements in this set that are also in the specified
 212:    * collection (optional operation). If the argument is also a set, this
 213:    * performs the <i>intersection</i> of the two sets.
 214:    *
 215:    * @param c the collection to keep
 216:    * @return true if this set was modified
 217:    * @throws UnsupportedOperationException if this operation is not allowed
 218:    * @throws NullPointerException if c is null
 219:    * @throws ClassCastException if the type of any element in c is not
 220:    *         a valid type for this set.
 221:    * @throws NullPointerException if some element of c is null and this
 222:    *         set doesn't support retaining null values.
 223:    * @see #remove(Object)
 224:    */
 225:   boolean retainAll(Collection c);
 226: 
 227:   /**
 228:    * Returns the number of elements in the set. If there are more
 229:    * than Integer.MAX_VALUE mappings, return Integer.MAX_VALUE. This is
 230:    * the <i>cardinality</i> of the set.
 231:    *
 232:    * @return the number of elements
 233:    */
 234:   int size();
 235: 
 236:   /**
 237:    * Returns an array containing the elements of this set. If the set
 238:    * makes a guarantee about iteration order, the array has the same
 239:    * order. The array is distinct from the set; modifying one does not
 240:    * affect the other.
 241:    *
 242:    * @return an array of this set's elements
 243:    * @see #toArray(Object[])
 244:    */
 245:   Object[] toArray();
 246: 
 247:   /**
 248:    * Returns an array containing the elements of this set, of the same runtime
 249:    * type of the argument. If the given set is large enough, it is reused,
 250:    * and null is inserted in the first unused slot. Otherwise, reflection
 251:    * is used to build a new array. If the set makes a guarantee about iteration
 252:    * order, the array has the same order. The array is distinct from the set;
 253:    * modifying one does not affect the other.
 254:    *
 255:    * @param a the array to determine the return type; if it is big enough
 256:    *        it is used and returned
 257:    * @return an array holding the elements of the set
 258:    * @throws ArrayStoreException if the runtime type of a is not a supertype
 259:    *         of all elements in the set
 260:    * @throws NullPointerException if a is null
 261:    * @see #toArray()
 262:    */
 263:   Object[] toArray(Object[] a);
 264: }