TurboStringMap for Gwt

In my previous post I did mention that Gwt has the basic Java collections emulated in Javascript. In the browser such rich interfaces may not be needed. There is a lightweight Map implementation where the keys are constrained to String types only called FastStringMap. It is directly backed by a Js array. Want to go even lighter then here is the derived TurboStringMap which even a thinner API over a Js array to act like a Map.

The rest of the this post is Gwt Java code-

package com.onyem.finance.client;

import com.google.gwt.core.client.JavaScriptObject;

class TurboStringMap {

 /*
 * Accesses need to be prefixed with ':' to prevent conflict with built-in
 * JavaScript properties.
 */
@SuppressWarnings("unused")
private JavaScriptObject map;

public TurboStringMap() {
 init();
}

public void clear() {
 init();
}

private native void init() /*-{
   this.@com.onyem.finance.client.TurboStringMap::map = {};
 }-*/;

// Prepend ':' to avoid conflicts with built-in Object properties.
public native T get(String key) /*-{
   return this.@com.onyem.finance.client.TurboStringMap::map[':' + key];
 }-*/;

// Prepend ':' to avoid conflicts with built-in Object properties.
public native T put(String key, T value) /*-{
   key = ':' + key;
   var map = this.@com.onyem.finance.client.TurboStringMap::map;
   var previous = map[key];
   map[key] = value;
   return previous;
 }-*/;

// Prepend ':' to avoid conflicts with built-in Object properties.
public native T remove(String key) /*-{
   key = ':' + key;
   var map = this.@com.onyem.finance.client.TurboStringMap::map;
   var previous = map[key];
   delete map[key];
   return previous;
 }-*/;

// only count keys with ':' prefix
public native int size() /*-{
   var value = this.@com.onyem.finance.client.TurboStringMap::map;
   var count = 0;
   for(var key in value) {
     if (key.charAt(0) == ':') ++count;
   }
   return count;
 }-*/;

public boolean isEmpty() {
 return size() == 0;
}

public native String[] keys() /*-{
   var value = this.@com.onyem.finance.client.TurboStringMap::map;
   var keys = [];
   for(var key in value) {
     keys.push(key.substring(1));
   }
   return keys;
}-*/;
}