Trying to implement the below code without using Stream

Since I’m using JDK 1.8 the below code works file on my local. But this will fail in deployment as VM uses JDK 1.7 and doesn’t understand stream.

public static String buildQuery(Map<String, String> dimensions, Map<String, String> measures,
            List<Constraint> constraints, final RequestMode requestMode, String queryMode, String reportName,
            String table) {

        queryMode = StringUtils.isEmpty(queryMode) ? "sync" : queryMode;
        final List<FilterDefinition> filters;
        if (CollectionUtils.isNotEmpty(constraints)) {
            filters = constraints.stream().map(FilterDefinition::new).collect(Collectors.toList());
        } else {
            filters = new ArrayList<>();
        }
        
        final QueryDefinition queryDefinition = new QueryDefinition(createColumnList(dimensions),
                createColumnList(measures), filters, requestMode.name(), table);

        return gson.toJson(new Request(queryMode, reportName, queryDefinition));
    }

How to modify this to get the same output, but without stream?

>Solution :

Ok, step-by-step:

1. stream() we have to convert into a for/while loop:

   so:

   constraints.stream()...
   

   gets to:

   for (Constraint c : constraints) { ... }
   

2. The map() we "convert" inside the loop. For each Constraint it should construct us a new FilterDefinition(c))

   so:

   ...map(FilterDefinition::new)...
   

   gets to:

   ... { ... (new FilterDefinition(c)) ...}
   

3. The collect(toList()) we accomplish by creating and (consequently) adding to our list.

   so:

   .collect(Collectors.toList())
   

   gets to:

   filters = new ArrayList<>();
   for ... {
       filters.add(...);
   }
   

Combining it all, should get us:

...
final List<FilterDefinition> filters = new ArrayList<>();
if (CollectionUtils.isNotEmpty(constraints)) {
  for (Constraint c : constraints) {
    filters.add(new FilterDefinition(c));
  }
} // when we initialized the list already, we don't need the "else"!