Compact way to build a String starting at null using +=
<p>I would like to use the following compact way to build a <code>String</code>:</p>

<pre><code>String attributes = null;
for (Map.Entry&lt;String, String&gt; kvp : attrs.entrySet())
  attributes += (kvp.getKey() + "='" + kvp.getValue() +"' ");
</code></pre>

<p>but the result is a String which reads: <code>nullattr1='val1' attr2='val2' attr3='val3'</code>. I presume that this is happening as a result of performing a <code>+=</code> operation on a <code>String</code> whose current value is null. Is there no compact way to do this without having to check if <code>attributes</code> is null each time through the loop?</p>
