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1: /* Set.java -- A collection that prohibits duplicates 2: Copyright (C) 1998, 2001, 2004, 2005 3: Free Software Foundation, Inc. 4: 5: This file is part of GNU Classpath. 6: 7: GNU Classpath is free software; you can redistribute it and/or modify 8: it under the terms of the GNU General Public License as published by 9: the Free Software Foundation; either version 2, or (at your option) 10: any later version. 11: 12: GNU Classpath is distributed in the hope that it will be useful, but 13: WITHOUT ANY WARRANTY; without even the implied warranty of 14: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15: General Public License for more details. 16: 17: You should have received a copy of the GNU General Public License 18: along with GNU Classpath; see the file COPYING. If not, write to the 19: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 20: 02110-1301 USA. 21: 22: Linking this library statically or dynamically with other modules is 23: making a combined work based on this library. Thus, the terms and 24: conditions of the GNU General Public License cover the whole 25: combination. 26: 27: As a special exception, the copyright holders of this library give you 28: permission to link this library with independent modules to produce an 29: executable, regardless of the license terms of these independent 30: modules, and to copy and distribute the resulting executable under 31: terms of your choice, provided that you also meet, for each linked 32: independent module, the terms and conditions of the license of that 33: module. An independent module is a module which is not derived from 34: or based on this library. If you modify this library, you may extend 35: this exception to your version of the library, but you are not 36: obligated to do so. If you do not wish to do so, delete this 37: exception statement from your version. */ 38: 39: 40: package java.util; 41: 42: /** 43: * A collection that contains no duplicates. In other words, for two set 44: * elements e1 and e2, <code>e1.equals(e2)</code> returns false. There 45: * are additional stipulations on <code>add</code>, <code>equals</code> 46: * and <code>hashCode</code>, as well as the requirements that constructors 47: * do not permit duplicate elements. The Set interface is incompatible with 48: * List; you cannot implement both simultaneously. 49: * <p> 50: * 51: * Note: Be careful about using mutable objects in sets. In particular, 52: * if a mutable object changes to become equal to another set element, you 53: * have violated the contract. As a special case of this, a Set is not 54: * allowed to be an element of itself, without risking undefined behavior. 55: * 56: * @author Original author unknown 57: * @author Eric Blake (ebb9@email.byu.edu) 58: * @see Collection 59: * @see List 60: * @see SortedSet 61: * @see HashSet 62: * @see TreeSet 63: * @see LinkedHashSet 64: * @see AbstractSet 65: * @see Collections#singleton(Object) 66: * @see Collections#EMPTY_SET 67: * @since 1.2 68: * @status updated to 1.4 69: */ 70: public interface Set<E> extends Collection<E> 71: { 72: /** 73: * Adds the specified element to the set if it is not already present 74: * (optional operation). In particular, the comparison algorithm is 75: * <code>o == null ? e == null : o.equals(e)</code>. Sets need not permit 76: * all values, and may document what exceptions will be thrown if 77: * a value is not permitted. 78: * 79: * @param o the object to add 80: * @return true if the object was not previously in the set 81: * @throws UnsupportedOperationException if this operation is not allowed 82: * @throws ClassCastException if the class of o prevents it from being added 83: * @throws IllegalArgumentException if some aspect of o prevents it from 84: * being added 85: * @throws NullPointerException if null is not permitted in this set 86: */ 87: boolean add(E o); 88: 89: /** 90: * Adds all of the elements of the given collection to this set (optional 91: * operation). If the argument is also a Set, this returns the mathematical 92: * <i>union</i> of the two. The behavior is unspecified if the set is 93: * modified while this is taking place. 94: * 95: * @param c the collection to add 96: * @return true if the set changed as a result 97: * @throws UnsupportedOperationException if this operation is not allowed 98: * @throws ClassCastException if the class of an element prevents it from 99: * being added 100: * @throws IllegalArgumentException if something about an element prevents 101: * it from being added 102: * @throws NullPointerException if null is not permitted in this set, or 103: * if the argument c is null 104: * @see #add(Object) 105: */ 106: boolean addAll(Collection<? extends E> c); 107: 108: /** 109: * Removes all elements from this set (optional operation). This set will 110: * be empty afterwords, unless an exception occurs. 111: * 112: * @throws UnsupportedOperationException if this operation is not allowed 113: */ 114: void clear(); 115: 116: /** 117: * Returns true if the set contains the specified element. In other words, 118: * this looks for <code>o == null ? e == null : o.equals(e)</code>. 119: * 120: * @param o the object to look for 121: * @return true if it is found in the set 122: * @throws ClassCastException if the type of o is not a valid type 123: * for this set. 124: * @throws NullPointerException if o is null and this set doesn't 125: * support null values. 126: */ 127: boolean contains(Object o); 128: 129: /** 130: * Returns true if this set contains all elements in the specified 131: * collection. If the argument is also a set, this is the <i>subset</i> 132: * relationship. 133: * 134: * @param c the collection to check membership in 135: * @return true if all elements in this set are in c 136: * @throws NullPointerException if c is null 137: * @throws ClassCastException if the type of any element in c is not 138: * a valid type for this set. 139: * @throws NullPointerException if some element of c is null and this 140: * set doesn't support null values. 141: * @see #contains(Object) 142: */ 143: boolean containsAll(Collection<?> c); 144: 145: /** 146: * Compares the specified object to this for equality. For sets, the object 147: * must be a set, the two must have the same size, and every element in 148: * one must be in the other. 149: * 150: * @param o the object to compare to 151: * @return true if it is an equal set 152: */ 153: boolean equals(Object o); 154: 155: /** 156: * Returns the hash code for this set. In order to satisfy the contract of 157: * equals, this is the sum of the hashcode of all elements in the set. 158: * 159: * @return the sum of the hashcodes of all set elements 160: * @see #equals(Object) 161: */ 162: int hashCode(); 163: 164: /** 165: * Returns true if the set contains no elements. 166: * 167: * @return true if the set is empty 168: */ 169: boolean isEmpty(); 170: 171: /** 172: * Returns an iterator over the set. The iterator has no specific order, 173: * unless further specified. 174: * 175: * @return a set iterator 176: */ 177: Iterator<E> iterator(); 178: 179: /** 180: * Removes the specified element from this set (optional operation). If 181: * an element e exists, <code>o == null ? e == null : o.equals(e)</code>, 182: * it is removed from the set. 183: * 184: * @param o the object to remove 185: * @return true if the set changed (an object was removed) 186: * @throws UnsupportedOperationException if this operation is not allowed 187: * @throws ClassCastException if the type of o is not a valid type 188: * for this set. 189: * @throws NullPointerException if o is null and this set doesn't allow 190: * the removal of a null value. 191: */ 192: boolean remove(Object o); 193: 194: /** 195: * Removes from this set all elements contained in the specified collection 196: * (optional operation). If the argument is a set, this returns the 197: * <i>asymmetric set difference</i> of the two sets. 198: * 199: * @param c the collection to remove from this set 200: * @return true if this set changed as a result 201: * @throws UnsupportedOperationException if this operation is not allowed 202: * @throws NullPointerException if c is null 203: * @throws ClassCastException if the type of any element in c is not 204: * a valid type for this set. 205: * @throws NullPointerException if some element of c is null and this 206: * set doesn't support removing null values. 207: * @see #remove(Object) 208: */ 209: boolean removeAll(Collection<?> c); 210: 211: /** 212: * Retains only the elements in this set that are also in the specified 213: * collection (optional operation). If the argument is also a set, this 214: * performs the <i>intersection</i> of the two sets. 215: * 216: * @param c the collection to keep 217: * @return true if this set was modified 218: * @throws UnsupportedOperationException if this operation is not allowed 219: * @throws NullPointerException if c is null 220: * @throws ClassCastException if the type of any element in c is not 221: * a valid type for this set. 222: * @throws NullPointerException if some element of c is null and this 223: * set doesn't support retaining null values. 224: * @see #remove(Object) 225: */ 226: boolean retainAll(Collection<?> c); 227: 228: /** 229: * Returns the number of elements in the set. If there are more 230: * than Integer.MAX_VALUE mappings, return Integer.MAX_VALUE. This is 231: * the <i>cardinality</i> of the set. 232: * 233: * @return the number of elements 234: */ 235: int size(); 236: 237: /** 238: * Returns an array containing the elements of this set. If the set 239: * makes a guarantee about iteration order, the array has the same 240: * order. The array is distinct from the set; modifying one does not 241: * affect the other. 242: * 243: * @return an array of this set's elements 244: * @see #toArray(Object[]) 245: */ 246: Object[] toArray(); 247: 248: /** 249: * Returns an array containing the elements of this set, of the same runtime 250: * type of the argument. If the given set is large enough, it is reused, 251: * and null is inserted in the first unused slot. Otherwise, reflection 252: * is used to build a new array. If the set makes a guarantee about iteration 253: * order, the array has the same order. The array is distinct from the set; 254: * modifying one does not affect the other. 255: * 256: * @param a the array to determine the return type; if it is big enough 257: * it is used and returned 258: * @return an array holding the elements of the set 259: * @throws ArrayStoreException if the runtime type of a is not a supertype 260: * of all elements in the set 261: * @throws NullPointerException if a is null 262: * @see #toArray() 263: */ 264: <T> T[] toArray(T[] a); 265: }