Package com.puppycrawl.tools.checkstyle.checks.coding

Class IllegalInstantiationCheck

java.lang.Object
com.puppycrawl.tools.checkstyle.api.AutomaticBean
com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
com.puppycrawl.tools.checkstyle.api.AbstractCheck
com.puppycrawl.tools.checkstyle.checks.coding.IllegalInstantiationCheck
All Implemented Interfaces:
Configurable, Contextualizable
public class IllegalInstantiationCheck extends AbstractCheck

Checks for illegal instantiations where a factory method is preferred.

Rationale: Depending on the project, for some classes it might be preferable to create instances through factory methods rather than calling the constructor.

A simple example is the java.lang.Boolean class. For performance reasons, it is preferable to use the predefined constants TRUE and FALSE. Constructor invocations should be replaced by calls to Boolean.valueOf().

Some extremely performance sensitive projects may require the use of factory methods for other classes as well, to enforce the usage of number caches or object pools.

There is a limitation that it is currently not possible to specify array classes.

  • Property classes - Specify fully qualified class names that should not be instantiated. Type is java.lang.String[]. Default value is "".
  • Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: CLASS_DEF.

To configure the check to find instantiations of java.lang.Boolean: 

 <module name="IllegalInstantiation">
   <property name="classes" value="java.lang.Boolean"/>
 </module>

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

  • instantiation.avoid
Since:
3.0

  • Field Details

    • MSG_KEY

      public static final String MSG_KEY
      A key is pointing to the warning message text in "messages.properties" file.
      See Also:

  • Constructor Details

    • IllegalInstantiationCheck

      public IllegalInstantiationCheck()

  • Method Details

    • getDefaultTokens

      public int[] getDefaultTokens()
      Description copied from class: AbstractCheck
      Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.
      Specified by:
      getDefaultTokens in class AbstractCheck
      Returns:
      the default tokens
      See Also:

    • getAcceptableTokens

      public int[] getAcceptableTokens()
      Description copied from class: AbstractCheck
      The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.
      Specified by:
      getAcceptableTokens in class AbstractCheck
      Returns:
      the token set this check is designed for.
      See Also:

    • getRequiredTokens

      public int[] getRequiredTokens()
      Description copied from class: AbstractCheck
      The tokens that this check must be registered for.
      Specified by:
      getRequiredTokens in class AbstractCheck
      Returns:
      the token set this must be registered for.
      See Also:

    • beginTree

      public void beginTree(DetailAST rootAST)
      Description copied from class: AbstractCheck
      Called before the starting to process a tree. Ideal place to initialize information that is to be collected whilst processing a tree.
      Overrides:
      beginTree in class AbstractCheck
      Parameters:
      rootAST - the root of the tree

    • visitToken

      public void visitToken(DetailAST ast)
      Description copied from class: AbstractCheck
      Called to process a token.
      Overrides:
      visitToken in class AbstractCheck
      Parameters:
      ast - the token to process

    • finishTree

      public void finishTree(DetailAST rootAST)
      Description copied from class: AbstractCheck
      Called after finished processing a tree. Ideal place to report on information collected whilst processing a tree.
      Overrides:
      finishTree in class AbstractCheck
      Parameters:
      rootAST - the root of the tree

    • setClasses

      public void setClasses(String... names)
      Setter to specify fully qualified class names that should not be instantiated.
      Parameters:
      names - a comma separate list of class names