Use of 'Properties' object as a 'Hashtable'

Reports calls to the following methods on java.util.Properties objects:

put()
putIfAbsent()
putAll()
get()

For historical reasons, java.util.Properties inherits from java.util.Hashtable, but using these methods is discouraged to prevent pollution of properties with values of types other than String.

Calls to java.util.Properties.putAll() won't get reported when both the key and the value parameters in the map are of the String type. Such a call is safe and no better alternative exists.

Example:

  Object f(Properties props) {
    props.put("hello", "world");
    props.putIfAbsent("hello", "world");
    props.putAll(new HashMap<>());
    return props.get("Hello");
  }

After the quick-fix is applied:

  Object f(Properties props) {
    props.setProperty("hello", "world");
    props.putIfAbsent("hello", "world");
    props.putAll(new HashMap<>());
    return props.getProperty("hello");
  }

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.

UseOfPropertiesAsHashtable

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 | Probable bugs

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 UseOfPropertiesAsHashtable

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