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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: }