Inspectopedia
 
2024.3

Assignment or return of field with mutable type

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Last modified: 03 December 2024

Reports return of, or assignment from a method parameter to an array or a mutable type like Collection, Date, Map, Calendar, etc.

Because such types are mutable, this construct may result in unexpected modifications of an object's state from outside the owning class. Although this construct may be useful for performance reasons, it is inherently prone to bugs.

The following mutable types are reported:

  • java.util.Date

  • java.util.Calendar

  • java.util.Collection

  • java.util.Map

  • com.google.common.collect.Multimap

  • com.google.common.collect.Table

The quick-fix adds a call to the field's .clone() method.

Example:

After the quick-fix is applied:

Use the Ignore assignments in and returns from private methods option to ignore assignments and returns in private methods.