It’s a common pattern to test the result of a java.util.Map.get() against null or calling
java.util.Map.containsKey() before proceeding with adding or changing the value in the map. However the java.util.Map API
offers a significantly better alternative in the form of the computeIfPresent() and computeIfAbsent() methods. Using these
instead leads to cleaner and more readable code.
Note that this rule is automatically disabled when the project’s sonar.java.source is not 8.
Noncompliant code example
V value = map.get(key);
if (value == null) { // Noncompliant
value = V.createFor(key);
if (value != null) {
map.put(key, value);
}
}
if (!map.containsKey(key)) { // Noncompliant
value = V.createFor(key);
if (value != null) {
map.put(key, value);
}
}
return value;
Compliant solution
return map.computeIfAbsent(key, k -> V.createFor(k));
Exceptions
This rule will not raise an issue when trying to add null to a map, because computeIfAbsent will not add the entry if the
value returned by the function is null.
