chainstringbuilderappendcalls.md

Chain StringBuilder.append() calls

org.openrewrite.staticanalysis.ChainStringBuilderAppendCalls

String concatenation within calls to StringBuilder.append() causes unnecessary memory allocation. Except for concatenations of String literals, which are joined together at compile time. Replaces inefficient concatenations with chained calls to StringBuilder.append().

Source

GitHub, Issue Tracker, Maven Central

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

Examples

Example 1

Chain StringBuilder.append() calls instead of the '+' operator to efficiently concatenate strings and numbers.

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

Before

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

class A {
    void method1() {
        StringBuilder sb = new StringBuilder();
        String op = "+";
        sb.append("A" + op + "B");
        sb.append(1 + op + 2);
    }
}

{% endcode %}

After

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

class A {
    void method1() {
        StringBuilder sb = new StringBuilder();
        String op = "+";
        sb.append("A").append(op).append("B");
        sb.append(1).append(op).append(2);
    }
}

{% endcode %}

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

--- A.java
+++ A.java
@@ -5,2 +5,2 @@
        StringBuilder sb = new StringBuilder();
        String op = "+";
-       sb.append("A" + op + "B");
-       sb.append(1 + op + 2);
+       sb.append("A").append(op).append("B");
+       sb.append(1).append(op).append(2);
    }

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

---

Example 2

Grouping concatenation.

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

Before

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

class A {
    void method1() {
        StringBuilder sb = new StringBuilder();
        String op = "+";
        sb.append("A" + "B" + "C" + op + "D" + "E");
    }
}

{% endcode %}

After

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

class A {
    void method1() {
        StringBuilder sb = new StringBuilder();
        String op = "+";
        sb.append("A" + "B" + "C").append(op).append("D" + "E");
    }
}

{% endcode %}

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

--- A.java
+++ A.java
@@ -5,1 +5,1 @@
        StringBuilder sb = new StringBuilder();
        String op = "+";
-       sb.append("A" + "B" + "C" + op + "D" + "E");
+       sb.append("A" + "B" + "C").append(op).append("D" + "E");
    }

{% 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.ChainStringBuilderAppendCalls")
}

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.ChainStringBuilderAppendCalls</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.ChainStringBuilderAppendCalls

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

Contributors

• Kun Li
• Knut Wannheden
• Sam Snyder

See how this recipe works across multiple open-source repositories

The community edition of the Moderne platform enables you to easily run recipes across thousands of open-source repositories.

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