Loop can be collapsed with Stream API

Reports loops which can be replaced with stream API calls using lambda expressions.

Such a replacement changes the style from imperative to more functional and makes the code more compact.

Example:

  boolean check(List<String> data) {
    for (String e : data) {
      String trimmed = e.trim();
      if (!trimmed.startsWith("xyz")) {
        return false;
      }
    }
    return true;
  }

After the quick-fix is applied:

  boolean check(List<String> data) {
    return data.stream().map(String::trim).allMatch(trimmed -> trimmed.startsWith("xyz"));
  }

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.

Convert2streamapi

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.

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 Loop can be collapsed with Stream API inspection, and the reference of their default values.

Warn if only 'forEach' replacement is available: Default value:
Not selected
Warn if the loop is trivial: 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 Convert2streamapi

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