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

Class EqualsAvoidNullCheck

java.lang.Object
com.puppycrawl.tools.checkstyle.AbstractAutomaticBean
com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
com.puppycrawl.tools.checkstyle.api.AbstractCheck
com.puppycrawl.tools.checkstyle.checks.coding.EqualsAvoidNullCheck
All Implemented Interfaces:
Configurable, Contextualizable
public class EqualsAvoidNullCheck extends AbstractCheck
Checks that any combination of String literals is on the left side of an equals() comparison. Also checks for String literals assigned to some field (such as someString.equals(anotherString = "text")).

Rationale: Calling the equals() method on String literals will avoid a potential NullPointerException. Also, it is pretty common to see null checks right before equals comparisons but following this rule such checks are not required.

  • Property ignoreEqualsIgnoreCase - Control whether to ignore String.equalsIgnoreCase(String) invocations. Type is boolean. Default value is false.

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

  • equals.avoid.null
  • equalsIgnoreCase.avoid.null
Since:
5.0

  • Field Details

  • Constructor Details

  • 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:

    • setIgnoreEqualsIgnoreCase

      public void setIgnoreEqualsIgnoreCase(boolean newValue)
      Setter to control whether to ignore String.equalsIgnoreCase(String) invocations.
      Parameters:
      newValue - whether to ignore checking String.equalsIgnoreCase(String).
      Since:
      5.4

    • 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

    • leaveToken

      public void leaveToken(DetailAST ast)
      Description copied from class: AbstractCheck
      Called after all the child nodes have been process.
      Overrides:
      leaveToken in class AbstractCheck
      Parameters:
      ast - the token leaving

    • finishTree

      public void finishTree(DetailAST ast)
      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:
      ast - the root of the tree

    • processSlist

      private void processSlist(DetailAST ast)
      Determine whether SLIST begins a block, determined by braces, and add it as a frame in this case.
      Parameters:
      ast - SLIST ast.

    • leaveSlist

      private void leaveSlist(DetailAST ast)
      Determine whether SLIST begins a block, determined by braces.
      Parameters:
      ast - SLIST ast.

    • processFrame

      private void processFrame(DetailAST ast)
      Process CLASS_DEF, METHOD_DEF, LITERAL_IF, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO, LITERAL_CATCH, LITERAL_TRY, CTOR_DEF, ENUM_DEF, ENUM_CONSTANT_DEF.
      Parameters:
      ast - processed ast.

    • processMethodCall

      private void processMethodCall(DetailAST methodCall)
      Add the method call to the current frame if it should be processed.
      Parameters:
      methodCall - METHOD_CALL ast.

    • processLiteralNew

      private void processLiteralNew(DetailAST ast)
      Determine whether LITERAL_NEW is an anonymous class definition and add it as a frame in this case.
      Parameters:
      ast - LITERAL_NEW ast.

    • leaveLiteralNew

      private void leaveLiteralNew(DetailAST ast)
      Determine whether LITERAL_NEW is an anonymous class definition and leave the frame it is in.
      Parameters:
      ast - LITERAL_NEW ast.

    • traverseFieldFrameTree

      private void traverseFieldFrameTree(EqualsAvoidNullCheck.FieldFrame frame)
      Traverse the tree of the field frames to check all equals method calls.
      Parameters:
      frame - to check method calls in.

    • checkMethodCall

      private void checkMethodCall(DetailAST methodCall)
      Check whether the method call should be violated.
      Parameters:
      methodCall - method call to check.

    • containsOneArgument

      private static boolean containsOneArgument(DetailAST methodCall)
      Verify that method call has one argument.
      Parameters:
      methodCall - METHOD_CALL DetailAST
      Returns:
      true if method call has one argument.

    • containsAllSafeTokens

      private static boolean containsAllSafeTokens(DetailAST expr)
      Looks for all "safe" Token combinations in the argument expression branch.
      Parameters:
      expr - the argument expression
      Returns:
      - true if any child matches the set of tokens, false if not

    • skipVariableAssign

      private static DetailAST skipVariableAssign(DetailAST currentAST)
      Skips over an inner assign portion of an argument expression.
      Parameters:
      currentAST - current token in the argument expression
      Returns:
      the next relevant token

    • isCalledOnStringFieldOrVariable

      private boolean isCalledOnStringFieldOrVariable(DetailAST objCalledOn)
      Determine, whether equals method is called on a field of String type.
      Parameters:
      objCalledOn - object ast.
      Returns:
      true if the object is of String type.

    • isStringFieldOrVariable

      private boolean isStringFieldOrVariable(DetailAST objCalledOn)
      Whether the field or the variable is of String type.
      Parameters:
      objCalledOn - the field or the variable to check.
      Returns:
      true if the field or the variable is of String type.

    • isStringFieldOrVariableFromThisInstance

      private boolean isStringFieldOrVariableFromThisInstance(DetailAST objCalledOn)
      Whether the field or the variable from THIS instance is of String type.
      Parameters:
      objCalledOn - the field or the variable from THIS instance to check.
      Returns:
      true if the field or the variable from THIS instance is of String type.

    • isStringFieldOrVariableFromClass

      private boolean isStringFieldOrVariableFromClass(DetailAST objCalledOn, String className)
      Whether the field or the variable from the specified class is of String type.
      Parameters:
      objCalledOn - the field or the variable from the specified class to check.
      className - the name of the class to check in.
      Returns:
      true if the field or the variable from the specified class is of String type.

    • getObjectFrame

      private static EqualsAvoidNullCheck.FieldFrame getObjectFrame(EqualsAvoidNullCheck.FieldFrame frame)
      Get the nearest parent frame which is CLASS_DEF, ENUM_DEF or ENUM_CONST_DEF.
      Parameters:
      frame - to start the search from.
      Returns:
      the nearest parent frame which is CLASS_DEF, ENUM_DEF or ENUM_CONST_DEF.

    • getFieldType

      private static String getFieldType(DetailAST field)
      Get field type.
      Parameters:
      field - to get the type from.
      Returns:
      type of the field.

    • astTypeIsClassOrEnumOrRecordDef

      private static boolean astTypeIsClassOrEnumOrRecordDef(int tokenType)
      Verify that a token is either CLASS_DEF, RECORD_DEF, or ENUM_DEF.
      Parameters:
      tokenType - the type of token
      Returns:
      true if token is of specified type.