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Moderne licensed

Replace java.util.Hashtable with java.util.HashMap

Recipe IDorg.openrewrite.staticanalysis.ReplaceHashtableWithHashMap
Artifactorg.openrewrite.recipe:rewrite-static-analysis

Hashtable synchronizes every operation, which adds overhead in the common single-threaded case. This recipe replaces a local Hashtable with a HashMap when data flow analysis can prove the Hashtable never escapes its method (it is not returned, assigned to a field, or passed as an argument), so no other thread can observe it and the synchronization is redundant. Fields, escaping variables, and Hashtable-specific method usages (contains, elements, keys) are left untouched. HashMap permits null keys and values, so it accepts every input Hashtable did.

Single recipeRSPEC-S1149MSAL

Usage

This recipe has no required configuration options. You’ll need the Moderne CLI configured before running the command below.

mod run . --recipe org.openrewrite.staticanalysis.ReplaceHashtableWithHashMap

If the recipe isn’t available locally, install it with:

mod config recipes jar install org.openrewrite.recipe:rewrite-static-analysis:2.40.0

Data tables

Structured output this recipe can produce.

  • Legacy synchronized types not migratedInstances of a legacy synchronized type (`Hashtable`, `Vector`, `Stack`, `StringBuffer`) that were found but left unchanged because they could not be proven safe to modernize.org.openrewrite.staticanalysis.table.LegacySynchronizedTypesNotMigrated
  • Source files that had resultsSource files that were modified by the recipe run.org.openrewrite.table.SourcesFileResults
  • Source files that had search resultsSearch results that were found during the recipe run.org.openrewrite.table.SearchResults
  • Source files that errored on a recipeThe details of all errors produced by a recipe run.org.openrewrite.table.SourcesFileErrors
  • Recipe performanceStatistics used in analyzing the performance of recipes.org.openrewrite.table.RecipeRunStats