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1: /* 2: * Written by Doug Lea with assistance from members of JCP JSR-166 3: * Expert Group and released to the public domain, as explained at 4: * http://creativecommons.org/licenses/publicdomain 5: */ 6: 7: package java.util.concurrent; 8: import java.util.Map; 9: 10: /** 11: * A {@link java.util.Map} providing additional atomic 12: * <tt>putIfAbsent</tt>, <tt>remove</tt>, and <tt>replace</tt> methods. 13: * 14: * <p>Memory consistency effects: As with other concurrent 15: * collections, actions in a thread prior to placing an object into a 16: * {@code ConcurrentMap} as a key or value 17: * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> 18: * actions subsequent to the access or removal of that object from 19: * the {@code ConcurrentMap} in another thread. 20: * 21: * <p>This interface is a member of the 22: * <a href="{@docRoot}/../technotes/guides/collections/index.html"> 23: * Java Collections Framework</a>. 24: * 25: * @since 1.5 26: * @author Doug Lea 27: * @param <K> the type of keys maintained by this map 28: * @param <V> the type of mapped values 29: */ 30: public interface ConcurrentMap<K, V> extends Map<K, V> { 31: /** 32: * If the specified key is not already associated 33: * with a value, associate it with the given value. 34: * This is equivalent to 35: * <pre> 36: * if (!map.containsKey(key)) 37: * return map.put(key, value); 38: * else 39: * return map.get(key);</pre> 40: * except that the action is performed atomically. 41: * 42: * @param key key with which the specified value is to be associated 43: * @param value value to be associated with the specified key 44: * @return the previous value associated with the specified key, or 45: * <tt>null</tt> if there was no mapping for the key. 46: * (A <tt>null</tt> return can also indicate that the map 47: * previously associated <tt>null</tt> with the key, 48: * if the implementation supports null values.) 49: * @throws UnsupportedOperationException if the <tt>put</tt> operation 50: * is not supported by this map 51: * @throws ClassCastException if the class of the specified key or value 52: * prevents it from being stored in this map 53: * @throws NullPointerException if the specified key or value is null, 54: * and this map does not permit null keys or values 55: * @throws IllegalArgumentException if some property of the specified key 56: * or value prevents it from being stored in this map 57: * 58: */ 59: V putIfAbsent(K key, V value); 60: 61: /** 62: * Removes the entry for a key only if currently mapped to a given value. 63: * This is equivalent to 64: * <pre> 65: * if (map.containsKey(key) && map.get(key).equals(value)) { 66: * map.remove(key); 67: * return true; 68: * } else return false;</pre> 69: * except that the action is performed atomically. 70: * 71: * @param key key with which the specified value is associated 72: * @param value value expected to be associated with the specified key 73: * @return <tt>true</tt> if the value was removed 74: * @throws UnsupportedOperationException if the <tt>remove</tt> operation 75: * is not supported by this map 76: * @throws ClassCastException if the key or value is of an inappropriate 77: * type for this map (optional) 78: * @throws NullPointerException if the specified key or value is null, 79: * and this map does not permit null keys or values (optional) 80: */ 81: boolean remove(Object key, Object value); 82: 83: /** 84: * Replaces the entry for a key only if currently mapped to a given value. 85: * This is equivalent to 86: * <pre> 87: * if (map.containsKey(key) && map.get(key).equals(oldValue)) { 88: * map.put(key, newValue); 89: * return true; 90: * } else return false;</pre> 91: * except that the action is performed atomically. 92: * 93: * @param key key with which the specified value is associated 94: * @param oldValue value expected to be associated with the specified key 95: * @param newValue value to be associated with the specified key 96: * @return <tt>true</tt> if the value was replaced 97: * @throws UnsupportedOperationException if the <tt>put</tt> operation 98: * is not supported by this map 99: * @throws ClassCastException if the class of a specified key or value 100: * prevents it from being stored in this map 101: * @throws NullPointerException if a specified key or value is null, 102: * and this map does not permit null keys or values 103: * @throws IllegalArgumentException if some property of a specified key 104: * or value prevents it from being stored in this map 105: */ 106: boolean replace(K key, V oldValue, V newValue); 107: 108: /** 109: * Replaces the entry for a key only if currently mapped to some value. 110: * This is equivalent to 111: * <pre> 112: * if (map.containsKey(key)) { 113: * return map.put(key, value); 114: * } else return null;</pre> 115: * except that the action is performed atomically. 116: * 117: * @param key key with which the specified value is associated 118: * @param value value to be associated with the specified key 119: * @return the previous value associated with the specified key, or 120: * <tt>null</tt> if there was no mapping for the key. 121: * (A <tt>null</tt> return can also indicate that the map 122: * previously associated <tt>null</tt> with the key, 123: * if the implementation supports null values.) 124: * @throws UnsupportedOperationException if the <tt>put</tt> operation 125: * is not supported by this map 126: * @throws ClassCastException if the class of the specified key or value 127: * prevents it from being stored in this map 128: * @throws NullPointerException if the specified key or value is null, 129: * and this map does not permit null keys or values 130: * @throws IllegalArgumentException if some property of the specified key 131: * or value prevents it from being stored in this map 132: */ 133: V replace(K key, V value); 134: }
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