Java tutorial
/* * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.script; import java.util.Map; import java.util.HashMap; import java.util.Collection; import java.util.Set; /** * A simple implementation of Bindings backed by * a {@code HashMap} or some other specified {@code Map}. * * @author Mike Grogan * @since 1.6 */ public class SimpleBindings implements Bindings { /** * The {@code Map} field stores the attributes. */ private Map<String, Object> map; /** * Constructor uses an existing {@code Map} to store the values. * @param m The {@code Map} backing this {@code SimpleBindings}. * @throws NullPointerException if m is null */ public SimpleBindings(Map<String, Object> m) { if (m == null) { throw new NullPointerException(); } this.map = m; } /** * Default constructor uses a {@code HashMap}. */ public SimpleBindings() { this(new HashMap<String, Object>()); } /** * Sets the specified key/value in the underlying {@code map} field. * * @param name Name of value * @param value Value to set. * * @return Previous value for the specified key. Returns null if key was previously * unset. * * @throws NullPointerException if the name is null. * @throws IllegalArgumentException if the name is empty. */ public Object put(String name, Object value) { checkKey(name); return map.put(name, value); } /** * {@code putAll} is implemented using {@code Map.putAll}. * * @param toMerge The {@code Map} of values to add. * * @throws NullPointerException * if toMerge map is null or if some key in the map is null. * @throws IllegalArgumentException * if some key in the map is an empty String. */ public void putAll(Map<? extends String, ? extends Object> toMerge) { if (toMerge == null) { throw new NullPointerException("toMerge map is null"); } for (Map.Entry<? extends String, ? extends Object> entry : toMerge.entrySet()) { String key = entry.getKey(); checkKey(key); put(key, entry.getValue()); } } /** {@inheritDoc} */ public void clear() { map.clear(); } /** * Returns {@code true} if this map contains a mapping for the specified * key. More formally, returns {@code true} if and only if * this map contains a mapping for a key {@code k} such that * {@code (key==null ? k==null : key.equals(k))}. (There can be * at most one such mapping.) * * @param key key whose presence in this map is to be tested. * @return {@code true} if this map contains a mapping for the specified * key. * * @throws NullPointerException if key is null * @throws ClassCastException if key is not String * @throws IllegalArgumentException if key is empty String */ public boolean containsKey(Object key) { checkKey(key); return map.containsKey(key); } /** {@inheritDoc} */ public boolean containsValue(Object value) { return map.containsValue(value); } /** {@inheritDoc} */ public Set<Map.Entry<String, Object>> entrySet() { return map.entrySet(); } /** * Returns the value to which this map maps the specified key. Returns * {@code null} if the map contains no mapping for this key. A return * value of {@code null} does not <i>necessarily</i> indicate that the * map contains no mapping for the key; it's also possible that the map * explicitly maps the key to {@code null}. The {@code containsKey} * operation may be used to distinguish these two cases. * * <p>More formally, if this map contains a mapping from a key * {@code k} to a value {@code v} such that * {@code (key==null ? k==null : key.equals(k))}, * then this method returns {@code v}; otherwise * it returns {@code null}. (There can be at most one such mapping.) * * @param key key whose associated value is to be returned. * @return the value to which this map maps the specified key, or * {@code null} if the map contains no mapping for this key. * * @throws NullPointerException if key is null * @throws ClassCastException if key is not String * @throws IllegalArgumentException if key is empty String */ public Object get(Object key) { checkKey(key); return map.get(key); } /** {@inheritDoc} */ public boolean isEmpty() { return map.isEmpty(); } /** {@inheritDoc} */ public Set<String> keySet() { return map.keySet(); } /** * Removes the mapping for this key from this map if it is present * (optional operation). More formally, if this map contains a mapping * from key {@code k} to value {@code v} such that * {@code (key==null ? k==null : key.equals(k))}, that mapping * is removed. (The map can contain at most one such mapping.) * * <p>Returns the value to which the map previously associated the key, or * {@code null} if the map contained no mapping for this key. (A * {@code null} return can also indicate that the map previously * associated {@code null} with the specified key if the implementation * supports {@code null} values.) The map will not contain a mapping for * the specified key once the call returns. * * @param key key whose mapping is to be removed from the map. * @return previous value associated with specified key, or {@code null} * if there was no mapping for key. * * @throws NullPointerException if key is null * @throws ClassCastException if key is not String * @throws IllegalArgumentException if key is empty String */ public Object remove(Object key) { checkKey(key); return map.remove(key); } /** {@inheritDoc} */ public int size() { return map.size(); } /** {@inheritDoc} */ public Collection<Object> values() { return map.values(); } private void checkKey(Object key) { if (key == null) { throw new NullPointerException("key can not be null"); } if (!(key instanceof String)) { throw new ClassCastException("key should be a String"); } if (key.equals("")) { throw new IllegalArgumentException("key can not be empty"); } } }