Donald Raab questions

Donald Raab answers

• Elegant way of doing ruby inject in Java 8
• Convert List<Long> to Map<Long, Long> that counts occurrences
• Sum of int from list of object [duplicate]
• Grouping and summing a list into a map using Lambda
• Fold operation in Scala Vs Java 8
• Most efficient way to convert/flatten entire map to list (keys & values together , not separately)
• An efficient way to convert List<Integer> to int[] ( array ) without iteration
• Convert a for loop to concat String into a lambda expression
• Iterate over 2 lists in java
• String list get an item starting without loop