Jambolan:

Jambolan or Java plum, also known as jamun, is the dark purple fruit of a
large tree similar in size to a mango tree. The fruit is about 4 cm
(1/2–1 1/2 in) long and similar to a cherry . Each
fruit contains a seed surrounded by a thin layer of yellowish pulp. The pulp
is very juicy and acidic, and often has an undesirable astringent taste.

Selection
When selecting jambolan, look for fruits that are ripe, clean, wholesome
and without infestation. They are best picked off the tree. Fruits picked off
the ground should not be bruised and must be eaten immediately.
Storage
Wash fruits well and store in a cool place, preferably in small lots, as bigger
lots can encourage bruising and fermentation. For longer storage, juice and
freeze the juice.
Preparation
If eaten raw, wash well before eating. To make juice, separate the yellow
flesh from the seed (thrown away) and reduce to pulp with a blender. Ripe
jambolans can also be stewed with water and sugar. The astringent taste can
be reduced by soaking prior to cooking.
Food value
Jambolan contains minerals and some dietary fibre. One hundred grams of
the raw fruit provides 257 kJ or 61 kcal 
Use
Jambolans are usually eaten fresh. They can also be made into jams, juice,
preserves and wine.