added lambda example how to filter a collection
added lambda example how to find average from a collection
added lambda example how to convert list to map in java
added lambda example how to count booleans in list
updated method name
updated count elements in list using java 8 lambda
updated filter elements by type using java 8 lambda
updated filter map by entries using java 8 lambda
updated filter map by keys using java 8 lambda
updated filter map by values using java 8 lambda expression
updated filter null values from collection using java 8 lambda expression