Stream API call chain can be replaced with loop

Reports Stream API chains, Iterable.forEach(), and Map.forEach() calls that can be automatically converted into classical loops.

Example:

  String joinNonEmpty(List<String> list) {
    return list.stream() // Stream can be converted to loop
      .filter(s -> !s.isEmpty())
      .map(String::trim)
      .collect(Collectors.joining(", "));
  }

After the quick-fix is applied:

  String joinNonEmpty(List<String> list) {
    StringJoiner joiner = new StringJoiner(", ");
    for (String s : list) {
      if (!s.isEmpty()) {
        String trim = s.trim();
        joiner.add(trim);
      }
    }
    return joiner.toString();
  }

Note that sometimes this inspection might cause slight semantic changes. Special care should be taken when it comes to short-circuiting, as it's not specified how many elements will be actually read when the stream short-circuits.

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.

StreamToLoop

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

Configure the inspection:

Use the Iterate unknown Stream sources via Stream.iterator() option to suggest conversions for streams with unrecognized source. In this case, iterator will be created from the stream. For example, when checkbox is selected, the conversion will be suggested here:

  List<ProcessHandle> handles = ProcessHandle.allProcesses().collect(Collectors.toList());

In this case, the result will be as follows:

  List<ProcessHandle> handles = new ArrayList<>();
  for (Iterator<ProcessHandle> it = ProcessHandle.allProcesses().iterator(); it.hasNext(); ) {
    ProcessHandle allProcess = it.next();
    handles.add(allProcess);
  }

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

New in 2017.1

Inspection options

Here you can find the description of settings available for the Stream API call chain can be replaced with loop inspection, and the reference of their default values.

Iterate unknown Stream sources via Stream.iterator(): Not selected

Availability

By default bundled with: IntelliJ IDEA 2024.1, Qodana for JVM 2024.1,
Can be installed with plugin: Java, 241.18072

Last modified: 18 June 2024