Use Empty Array for Collection.toArray()

org.openrewrite.staticanalysis.ReplaceCollectionToArrayArgWithEmptyArray

_Changes new array creation with Collection#toArray(T[]) to use an empty array argument, which is better for performance.

According to the Collection#toArray(T[]) documentation:

If the collection fits in the specified array, it is returned therein.

However, although it's not intuitive, allocating a right-sized array ahead of time to pass to the API appears to be generally worse for performance according to benchmarking and JVM developers due to a number of implementation details in both Java and the virtual machine.

H2 achieved significant performance gains by switching to empty arrays instead pre-sized ones._

Recipe source

GitHub, Issue Tracker, Maven Central

• groupId: org.openrewrite.recipe

• artifactId: rewrite-static-analysis

• version: 1.5.0

Usage

This recipe has no required configuration options. It can be activated by adding a dependency on org.openrewrite.recipe:rewrite-static-analysis:1.5.0 in your build file or by running a shell command (in which case no build changes are needed):

Gradle

1. Add the following to your build.gradle file:

build.gradle

plugins {
    id("org.openrewrite.rewrite") version("6.12.0")
}

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

repositories {
    mavenCentral()
}

dependencies {
    rewrite("org.openrewrite.recipe:rewrite-static-analysis:1.5.0")
}

2. Run gradle rewriteRun to run the recipe.

Gradle init script

1. Create a file named init.gradle in the root of your project.

init.gradle

initscript {
    repositories {
        maven { url "https://plugins.gradle.org/m2" }
    }
    dependencies { classpath("org.openrewrite:plugin:6.12.0") }
}
rootProject {
    plugins.apply(org.openrewrite.gradle.RewritePlugin)
    dependencies {
        rewrite("org.openrewrite.recipe:rewrite-static-analysis:1.5.0")
    }
    rewrite {
        activeRecipe("org.openrewrite.staticanalysis.ReplaceCollectionToArrayArgWithEmptyArray")
    }
    afterEvaluate {
        if (repositories.isEmpty()) {
            repositories {
                mavenCentral()
            }
        }
    }
}

2. Run gradle --init-script init.gradle rewriteRun to run the recipe.

Maven POM

1. Add the following to your pom.xml file:

pom.xml

<project>
  <build>
    <plugins>
      <plugin>
        <groupId>org.openrewrite.maven</groupId>
        <artifactId>rewrite-maven-plugin</artifactId>
        <version>5.29.0</version>
        <configuration>
          <activeRecipes>
            <recipe>org.openrewrite.staticanalysis.ReplaceCollectionToArrayArgWithEmptyArray</recipe>
          </activeRecipes>
        </configuration>
        <dependencies>
          <dependency>
            <groupId>org.openrewrite.recipe</groupId>
            <artifactId>rewrite-static-analysis</artifactId>
            <version>1.5.0</version>
          </dependency>
        </dependencies>
      </plugin>
    </plugins>
  </build>
</project>

2. Run mvn rewrite:run to run the recipe.

Maven Command Line

shell

mvn -U org.openrewrite.maven:rewrite-maven-plugin:run -Drewrite.recipeArtifactCoordinates=org.openrewrite.recipe:rewrite-static-analysis:RELEASE -Drewrite.activeRecipes=org.openrewrite.staticanalysis.ReplaceCollectionToArrayArgWithEmptyArray

Moderne CLI

You will need to have configured the Moderne CLI on your machine before you can run the following command.

shell

mod run . --recipe ReplaceCollectionToArrayArgWithEmptyArray

See how this recipe works across multiple open-source repositories

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Please contact Moderne for more information about safely running the recipes on your own codebase in a private SaaS.

Contributors

jrivadeneira