Java tutorial
/* * Copyright 2007 Google Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); you may not * use this file except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. */ package com.google.gwt.coreext.client; import com.google.gwt.core.client.JavaScriptObject; import java.util.AbstractMap; import java.util.AbstractSet; import java.util.ArrayList; import java.util.Collection; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Set; /** * Special-case Map implementation which imposes limits on the types of keys * that can be used in return for much faster speed. In specific, only strings * that could be added to a JavaScript object as keys are valid. * @param <T> generic type */ public class IterableFastStringMap<T> extends AbstractMap<String, T> { /** * interface that allows for iteration through Object Map. * @param <T> */ public interface IterationCallBack<T> { void onIteration(String key, T obj); } private static class ImplMapEntry<T> implements Map.Entry<String, T> { private String key; private T value; ImplMapEntry(String key, T value) { this.key = key; this.value = value; } @Override public boolean equals(Object a) { if (a instanceof Map.Entry<?, ?>) { Map.Entry<?, ?> s = (Map.Entry<?, ?>) a; if (equalsWithNullCheck(key, s.getKey()) && equalsWithNullCheck(value, s.getValue())) { return true; } } return false; } // strip prefix from key public String getKey() { return key; } public T getValue() { return value; } @Override public int hashCode() { int keyHash = 0; int valueHash = 0; if (key != null) { keyHash = key.hashCode(); } if (value != null) { valueHash = value.hashCode(); } return keyHash ^ valueHash; } public T setValue(T object) { T old = value; value = object; return old; } private boolean equalsWithNullCheck(Object a, Object b) { if (a == b) { return true; } else if (a == null) { return false; } else { return a.equals(b); } } } /* * Accesses need to be prefixed with ':' to prevent conflict with built-in * JavaScript properties. */ private JavaScriptObject map; public IterableFastStringMap() { init(); } @Override public void clear() { init(); } @Override public boolean containsKey(Object key) { return containsKey(keyMustBeString(key), map); } @Override public boolean containsValue(Object arg0) { return values().contains(arg0); } @Override public Set<Map.Entry<String, T>> entrySet() { return new AbstractSet<Map.Entry<String, T>>() { @Override public boolean contains(Object key) { Map.Entry<?, ?> s = (Map.Entry<?, ?>) key; Object value = get(s.getKey()); if (value == null) { return value == s.getValue(); } else { return value.equals(s.getValue()); } } @Override public Iterator<Map.Entry<String, T>> iterator() { Iterator<Map.Entry<String, T>> custom = new Iterator<Map.Entry<String, T>>() { Iterator<String> keys = keySet().iterator(); public boolean hasNext() { return keys.hasNext(); } public Map.Entry<String, T> next() { String key = keys.next(); return new ImplMapEntry<T>(key, get(key)); } public void remove() { keys.remove(); } }; return custom; } @Override public int size() { return IterableFastStringMap.this.size(); } }; } @Override public T get(Object key) { return get(keyMustBeString(key)); } // Prepend ':' to avoid conflicts with built-in Object properties. public native T get(String key) /*-{ var value = this.@com.google.gwt.coreext.client.IterableFastStringMap::map[':' + key]; return (value == null) ? null : value; }-*/; @Override public boolean isEmpty() { return size() == 0; } public native void iterate(IterationCallBack<T> cb) /*-{ var objMap = this.@com.google.gwt.coreext.client.IterableFastStringMap::map; for (var key in objMap) { if (key.charAt(0) == ':') { cb.@com.google.gwt.coreext.client.IterableFastStringMap.IterationCallBack::onIteration(Ljava/lang/String;Ljava/lang/Object;)(key,objMap[key]); } } }-*/; @Override public Set<String> keySet() { return new AbstractSet<String>() { @Override public boolean contains(Object key) { return containsKey(key); } @Override public Iterator<String> iterator() { List<String> l = new ArrayList<String>(); addAllKeysFromJavascriptObject(l, map); return l.iterator(); } @Override public int size() { return IterableFastStringMap.this.size(); } }; } // Prepend ':' to avoid conflicts with built-in Object properties. @Override public native T put(String key, T widget) /*-{ var previous = this.@com.google.gwt.coreext.client.IterableFastStringMap::map[':' + key]; this.@com.google.gwt.coreext.client.IterableFastStringMap::map[':' + key] = widget; return (previous == null) ? null : previous; }-*/; @Override public void putAll(Map<? extends String, ? extends T> arg0) { for (Map.Entry<? extends String, ? extends T> entry : arg0.entrySet()) { put(entry.getKey(), entry.getValue()); } } @Override public T remove(Object key) { return remove(keyMustBeString(key)); } // only count keys with ':' prefix @Override public native int size() /*-{ var value = this.@com.google.gwt.coreext.client.IterableFastStringMap::map; var count = 0; for(var key in value) { if (key.charAt(0) == ':') ++count; } return count; }-*/; @Override public Collection<T> values() { List<T> values = new ArrayList<T>(); addAllValuesFromJavascriptObject(values, map); return values; } // only count keys with ':' prefix private native void addAllKeysFromJavascriptObject(Collection<String> s, JavaScriptObject javaScriptObject) /*-{ for(var key in javaScriptObject) { if (key.charAt(0) != ':') continue; s.@java.util.Collection::add(Ljava/lang/Object;)(key.substring(1)); } }-*/; // only count keys with ':' prefix private native void addAllValuesFromJavascriptObject(Collection<T> s, JavaScriptObject javaScriptObject) /*-{ for(var key in javaScriptObject) { if (key.charAt(0) != ':') continue; var value = javaScriptObject[key]; s.@java.util.Collection::add(Ljava/lang/Object;)(value); } }-*/; // Prepend ':' to avoid conflicts with built-in Object properties. private native boolean containsKey(String key, JavaScriptObject obj)/*-{ return obj[':' + key] !== undefined; }-*/; private native void init() /*-{ this.@com.google.gwt.coreext.client.IterableFastStringMap::map = []; }-*/; private String keyMustBeString(Object key) { if (key instanceof String) { return (String) key; } else { throw new IllegalArgumentException( this.getClass().getName() + " can only have Strings as keys, not" + key); } } // Prepend ':' to avoid conflicts with built-in Object properties. private native T remove(String key) /*-{ var previous = this.@com.google.gwt.coreext.client.IterableFastStringMap::map[':' + key]; delete this.@com.google.gwt.coreext.client.IterableFastStringMap::map[':' + key]; return (previous == null) ? null : previous; }-*/; }