java - how to print values for multiple keys in a hashmap? -

this question has answer here:

• hashmap: 1 key, multiple values 9 answers

i have hashmap hold k,v this:

hashmap<string, string> total=new hashmap<>(); 

this how im populating map:(in loop result of db table)

total.put(rs.getstring("id"), rs.getstring("name")); 

now, keys have multiple values, want print each key: key , value. this:

123   john  123   tom  123   jack  234   terry  234   jeniffer  345   jacob  555   sara 

how can please?

thanks

hashmap (and, in fact, classes implementing map) stores 1 value per key.

quoting javadoc of map:

an object maps keys values. map cannot contain duplicate keys; each key can map @ 1 value.

to store "multiple" values per key, need value type able store multiple values, e.g. collection list or set, map type might map<string, list<string>>.

it's little bit clumsy manage: have check if there collection associated key, add empty 1 if not, , add collection:

// instead of: map.put(key, value);  // ...you'd need like: if (!map.containskey(key)) {   map.put(key, new arraylist<string>()); } map.get(key).add(value); 

alternatively, there libraries guava provide multimap, more describe directly.