Subsequent steps can be fused into Stream API chain

Detects transformations outside a Stream API chain that could be incorporated into it.

Example:

  List<String> list = stream.collect(Collectors.toList());
  list.sort(null);
  return list.toArray(new String[list.size()]);

After the conversion:

return stream.sorted().toArray(String[]::new);

Note that sometimes the converted stream chain may replace explicit ArrayList with Collectors.toList() or explicit HashSet with Collectors.toSet(). The current library implementation uses these collections internally. However, this approach is not very reliable and might change in the future altering the semantics of your code.

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

FuseStreamOperations

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | Java | Code style issues

If you are concerned about it, use the Do not suggest 'toList()' or 'toSet()' collectors option to suggest Collectors.toCollection() instead of toList and toSet collectors.

This inspection depends on the Java feature 'Stream and Optional API', which is available since Java 8.

Inspection options

Here you can find the description of settings available for the Subsequent steps can be fused into Stream API chain inspection, and the reference of their default values.

Do not suggest 'toList()' or 'toSet()' collectors: Default value:
Not selected

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

//noinspection FuseStreamOperations

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

IntelliJ IDEA 2025.2

Inspection Details
By default bundled with:	IntelliJ IDEA 2025.2, Qodana for JVM 2025.2,

Last modified: 18 September 2025