Description

Attention: Elements that cannot have JavaDoc comments like local variables are not in the scope of this check even though a token type like VARIABLE_DEF would match them.

Attention: Annotations among modifiers are ignored (looks like false-negative) as there might be a problem with annotations for return types:

public @Nullable Long getStartTimeOrNull() { ... }

Such annotations are better to keep close to type. Due to limitations, Checkstyle can not examine the target of an annotation.

Example:

@Override
@Nullable
public String getNameIfPresent() { ... }
        

Properties

Examples

To configure the default check to allow one single parameterless annotation on the same line:

<module name="Checker">
  <module name="TreeWalker">
    <module name="AnnotationLocation"/>
  </module>
</module>
        

Example:

class Example1 {
  @Nonnull
  private boolean field1; // ok
  @Override public int hashCode() { return 1; } // ok
  @Nonnull // ok
  private boolean field2;
  @Override // ok
  public boolean equals(Object obj) { return true; }
  @Mock DataLoader loader1; // ok
  @SuppressWarnings("deprecation") DataLoader loader2;
  // violation above, 'Annotation 'SuppressWarnings' should be alone on line'
  @SuppressWarnings("deprecation") public int foo() { return 1; }
  // violation above, 'Annotation 'SuppressWarnings' should be alone on line'
  @Nonnull @Mock DataLoader loader3;
  // violation above, 'Annotation 'Mock' should be alone on line'
}
        

Use the following configuration to allow multiple annotations on the same line:

<module name="Checker">
  <module name="TreeWalker">
    <module name="AnnotationLocation">
      <property name="allowSamelineSingleParameterlessAnnotation"
                value="false"/>
      <property name="allowSamelineParameterizedAnnotation" value="false"/>
      <property name="allowSamelineMultipleAnnotations" value="true"/>
    </module>
  </module>
</module>
        

Example:

class Example2 {
  @Nonnull
  private boolean field1;
  @Override public int hashCode() { return 1; } // ok
  @Nonnull
  private boolean field2;
  @Override
  public boolean equals(Object obj) { return true; }
  @Mock
  DataLoader loader1;
  @SuppressWarnings("deprecation") DataLoader loader;
  @SuppressWarnings("deprecation") public int foo() { return 1; } // ok
  @Nonnull @Mock DataLoader loader2;
  // ok above as 'allowSamelineMultipleAnnotations' set to true
}
        

Use the following configuration to allow only one and only parameterized annotation on the same line:

<module name="Checker">
  <module name="TreeWalker">
    <module name="AnnotationLocation">
      <property name="allowSamelineMultipleAnnotations" value="false"/>
      <property name="allowSamelineSingleParameterlessAnnotation"
                value="false"/>
      <property name="allowSamelineParameterizedAnnotation" value="true"/>
    </module>
  </module>
</module>
        

Example:

class Example3 {
  // violation below, 'Annotation 'Nonnull' should be alone on line.'
  @Nonnull private boolean field1;
  // violation below, 'Annotation 'Override' should be alone on line.'
  @Override public int hashCode() { return 1; }
  @Nonnull
  private boolean field2;
  @Override
  public boolean equals(Object obj) { return true; }
  @Mock
  DataLoader loader;
  @SuppressWarnings("deprecation") DataLoader loader1;
  @SuppressWarnings("deprecation") public int foo() { return 1; }
  // violation below, 'Annotation 'Nonnull' should be alone on line.'
  @Nonnull @Mock DataLoader loader2;
  // violation above, 'Annotation 'Mock' should be alone on line.'
}
        

Use the following configuration to only validate annotations on methods to allow one single parameterless annotation on the same line:

<module name="Checker">
  <module name="TreeWalker">
    <module name="AnnotationLocation">
      <property name="tokens" value="METHOD_DEF"/>
      <property name="allowSamelineMultipleAnnotations" value="false"/>
      <property name="allowSamelineSingleParameterlessAnnotation"
                value="true"/>
      <property name="allowSamelineParameterizedAnnotation" value="false"/>
    </module>
  </module>
</module>
        

Example:

class Example4 {
  @NotNull private boolean field1; // ok, as 'tokens' property set to METHOD_DEF only
  @Override public int hashCode() { return 1; }
  @NotNull
  private boolean field2;
  @Override
  public boolean equals(Object obj) { return true; }
  @Mock
  DataLoader loader1;
  @SuppressWarnings("deprecation") DataLoader loader;
  @SuppressWarnings("deprecation") public int foo() { return 1; }
  // violation above, 'Annotation 'SuppressWarnings' should be alone on line.'
  @NotNull @Mock DataLoader loader2;
}
        

Example of Usage

• Google Style
• Checkstyle Style

Violation Messages

• annotation.location
• annotation.location.alone

All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.

Package

com.puppycrawl.tools.checkstyle.checks.annotation

Parent Module

TreeWalker