Moderne licensed

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

Recipe IDorg.openrewrite.staticanalysis.ReplaceHashtableWithHashMapArtifactorg.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

Add to your build

Get a download tokenThis recipe is Moderne licensed, so the token must belong to a Moderne customer. It replaces YOUR_DOWNLOAD_TOKEN below.

~/.gradle/gradle.properties

codeGenomeUsername=you@example.com
codeGenomeToken=YOUR_DOWNLOAD_TOKEN

build.gradle.kts

plugins {
    id("org.openrewrite.rewrite") version("latest.release")
}

rewrite {
    activeRecipe("org.openrewrite.staticanalysis.ReplaceHashtableWithHashMap")
}

repositories {
    mavenCentral()
    maven {
        url = uri("https://artifacts.codegenomeproject.org/maven")
        credentials {
            username = providers.gradleProperty("codeGenomeUsername").get()
            password = providers.gradleProperty("codeGenomeToken").get()
        }
    }
}

dependencies {
    rewrite("org.openrewrite.recipe:rewrite-static-analysis:2.44.0")
}

Then run

./gradlew rewriteRun

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:RELEASE

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