As said in JavaDocs:

If the mapped keys contains duplicates (according to Object.equals(Object)), an IllegalStateException is thrown when the collection operation is performed. If the mapped keys may have duplicates, use toMap(Function keyMapper, Function valueMapper, BinaryOperator mergeFunction) instead.

So you should use toMap(Function keyMapper, Function valueMapper, BinaryOperator mergeFunction) instead. Just provide a merge function, that will determine which one of duplicates is put in the map.

For example, if you don't care which one, just call

Map<String, String> phoneBook = people.stream().collect(
        Collectors.toMap(Person::getName, Person::getAddress, (a1, a2) -> a1));

Try using

list.stream.collect(Collectors.groupingBy(srv::Scriptinterfaceid))

This will return a map with Scriptinterfaceid as the Key & List<srv> as Value.

You can use groupingBy

getMapStream()
      .map(item -> Arrays.asList(item))
      .collect(Collectors.groupingBy(l->l.get(0),
           Collectors.mapping(l1->l1.get(1),Collectors.toList())));

or use toMap() with merge function.

     Map<String,List<String>> vehicle = getMapStream()
            .collect(Collectors.toMap(item->item[0],
       item->new ArrayList<>(Arrays.asList(item[1])),
                            (l1,l2)->{l1.addAll(l2);return l1;}));

You can use the distinct() method on Stream to eliminate the duplicates before further processing.

We don't need to depend on the Google Collections external library. You can simply implement the following Map:

Map<String, ArrayList<String>> hashMap = new HashMap<String, ArrayList>();

public static void main(String... arg) {
   // Add data with duplicate keys
   addValues("A", "a1");
   addValues("A", "a2");
   addValues("B", "b");
   // View data.
   Iterator it = hashMap.keySet().iterator();
   ArrayList tempList = null;

   while (it.hasNext()) {
      String key = it.next().toString();             
      tempList = hashMap.get(key);
      if (tempList != null) {
         for (String value: tempList) {
            System.out.println("Key : "+key+ " , Value : "+value);
         }
      }
   }
}

private void addValues(String key, String value) {
   ArrayList tempList = null;
   if (hashMap.containsKey(key)) {
      tempList = hashMap.get(key);
      if(tempList == null)
         tempList = new ArrayList();
      tempList.add(value);  
   } else {
      tempList = new ArrayList();
      tempList.add(value);               
   }
   hashMap.put(key,tempList);
}

Please make sure to fine tune the code.