Convert a map of maps into single list of values in java 8 : <p>I have a Map of map :</p>

<pre><code>Map&lt;Integer,Map&lt;String,Integer&gt;&gt;
</code></pre>

<p>I need this map to be flattened into just the list of values :</p>

<pre><code>Map&lt;String,Integer&gt; map1 = new HashMap&lt;&gt;();
Map&lt;String,Integer&gt; map2 = new HashMap&lt;&gt;();
map1.putIfAbsent("ABC",123);
map1.putIfAbsent("PQR",345);
map1.putIfAbsent("XYZ",567);
map2.putIfAbsent("ABC",234);
map2.putIfAbsent("FGH",789);
map2.putIfAbsent("BNM",890);
Map&lt;Integer,Map&lt;String,Integer&gt;&gt; mapMap = new HashMap();
mapMap.putIfAbsent(0,map1);
mapMap.putIfAbsent(1,map2);
</code></pre>

<p>Expected output :
123</p>

<p>345</p>

<p>567</p>

<p>234</p>

<p>789</p>

<p>890</p>

<p>I need different solution including java 8 streams!!</p>

<p>Thanks</p>
