usediamondoperator.md

Use diamond operator

org.openrewrite.staticanalysis.UseDiamondOperator

The diamond operator (<>) should be used. Java 7 introduced the diamond operator (<>) to reduce the verbosity of generics code. For instance, instead of having to declare a List's type in both its declaration and its constructor, you can now simplify the constructor declaration with <>, and the compiler will infer the type.

Tags

• RSPEC-2293

Source

GitHub, Issue Tracker, Maven Central

• groupId: org.openrewrite.recipe
• artifactId: rewrite-static-analysis
• version: 1.0.1

Example

{% tabs %} {% tab title="Test.java" %}

Before

{% code title="Test.java" %}

import java.util.*;

class Test<X, Y> {
    void test() {
        List<String> ls = new ArrayList<String>();
        Map<X,Y> map = new HashMap<X,Y>();
        List<String> ls2 = new ArrayList<String>() {
        };
    }
}

{% endcode %}

After

{% code title="Test.java" %}

import java.util.*;

class Test<X, Y> {
    void test() {
        List<String> ls = new ArrayList<>();
        Map<X,Y> map = new HashMap<>();
        List<String> ls2 = new ArrayList<String>() {
        };
    }
}

{% endcode %}

{% endtab %} {% tab title="Diff" %} {% code %}

--- Test.java
+++ Test.java
@@ -5,2 +5,2 @@
class Test<X, Y> {
    void test() {
-       List<String> ls = new ArrayList<String>();
-       Map<X,Y> map = new HashMap<X,Y>();
+       List<String> ls = new ArrayList<>();
+       Map<X,Y> map = new HashMap<>();
        List<String> ls2 = new ArrayList<String>() {

{% endcode %} {% endtab %} {% endtabs %}

Usage

This recipe has no required configuration options. It can be activated by adding a dependency on org.openrewrite.recipe:rewrite-static-analysis:1.0.1 in your build file or by running a shell command (in which case no build changes are needed): {% tabs %} {% tab title="Gradle" %} {% code title="build.gradle" %}

plugins {
    id("org.openrewrite.rewrite") version("6.1.4")
}

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

repositories {
    mavenCentral()
}

dependencies {
    rewrite("org.openrewrite.recipe:rewrite-static-analysis:1.0.1")
}

{% endcode %} {% endtab %} {% tab title="Maven POM" %} {% code title="pom.xml" %}

<project>
  <build>
    <plugins>
      <plugin>
        <groupId>org.openrewrite.maven</groupId>
        <artifactId>rewrite-maven-plugin</artifactId>
        <version>5.2.4</version>
        <configuration>
          <activeRecipes>
            <recipe>org.openrewrite.staticanalysis.UseDiamondOperator</recipe>
          </activeRecipes>
        </configuration>
        <dependencies>
          <dependency>
            <groupId>org.openrewrite.recipe</groupId>
            <artifactId>rewrite-static-analysis</artifactId>
            <version>1.0.1</version>
          </dependency>
        </dependencies>
      </plugin>
    </plugins>
  </build>
</project>

{% endcode %} {% endtab %}

{% tab title="Maven Command Line" %} {% code title="shell" %} You will need to have Maven installed on your machine before you can run the following command.

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

{% endcode %} {% endtab %} {% endtabs %}

Contributors

• Patrick Way
• Jonathan Schneider
• Knut Wannheden
• Kun Li
• Patrick
• Aaron Gershman
• Tyler Van Gorder
• Josh Soref
• Sam Snyder

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