Package org.eclipse.core.expressions

Class Expression

java.lang.Object
org.eclipse.core.expressions.Expression
Direct Known Subclasses:
ActiveShellExpression, CompositeExpression, CountExpression, EqualsExpression, LegacyHandlerSubmissionExpression, ReferenceExpression, TestExpression
public abstract class Expression extends Object
Abstract base class for all expressions provided by the common expression language.

An expression is evaluated by calling evaluate(IEvaluationContext).

This class may be subclassed to provide specific expressions.

Since:
3.0

  • Field Details

    • HASH_CODE_NOT_COMPUTED

      protected static final int HASH_CODE_NOT_COMPUTED
      The constant integer hash code value meaning the hash code has not yet been computed.
      See Also:

    • HASH_FACTOR

      protected static final int HASH_FACTOR
      A factor for computing the hash code for all expressions.
      See Also:

    • ATT_VALUE

      protected static final String ATT_VALUE
      Name of the value attribute of an expression (value is value).
      See Also:

    • TRUE

      public static final Expression TRUE
      The expression corresponding to EvaluationResult.TRUE.

    • FALSE

      public static final Expression FALSE
      The expression corresponding to EvaluationResult.FALSE.

  • Constructor Details

    • Expression

      public Expression()

  • Method Details

    • equals

      protected static final boolean equals(Object left, Object right)
      Checks whether two objects are equal using the equals(Object) method of the left object. This method handles null for either the left or right object.
      Parameters:
      left - the first object to compare; may be null.
      right - the second object to compare; may be null.
      Returns:
      true if the two objects are equivalent; false otherwise.
      Since:
      3.2

    • equals

      protected static final boolean equals(Object[] leftArray, Object[] rightArray)
      Tests whether two arrays of objects are equal to each other. The arrays must not be null, but their elements may be null.
      Parameters:
      leftArray - the left array to compare; may be null, and may be empty and may contain null elements.
      rightArray - the right array to compare; may be null, and may be empty and may contain null elements.
      Returns:
      true if the arrays are equal length and the elements at the same position are equal; false otherwise.
      Since:
      3.2

    • hashCode

      protected static final int hashCode(Object object)
      Returns the hash code for the given object. This method handles null.
      Parameters:
      object - the object for which the hash code is desired; may be null.
      Returns:
      The hash code of the object; zero if the object is null.
      Since:
      3.2

    • hashCode

      protected static final int hashCode(Object[] array)
      Returns the hash code for the given array. This method handles null.
      Parameters:
      array - the array for which the hash code is desired; may be null.
      Returns:
      the hash code of the array; zero if the object is null.
      Since:
      3.2

    • evaluate

      public abstract EvaluationResult evaluate(IEvaluationContext context) throws CoreException
      Evaluates this expression.
      Parameters:
      context - an evaluation context providing information like variable, name spaces, etc. necessary to evaluate this expression
      Returns:
      the result of the expression evaluation
      Throws:
      CoreException - if the evaluation failed. The concrete reason is defined by the subclass implementing this method

    • computeExpressionInfo

      public final ExpressionInfo computeExpressionInfo()
      Computes the expression information for the given expression tree.

      This is a convenience method for collecting the expression information using collectExpressionInfo(ExpressionInfo).

      Returns:
      the expression information
      Since:
      3.2

    • collectExpressionInfo

      public void collectExpressionInfo(ExpressionInfo info)
      Collects information about this expression tree. This default implementation add the expression's type to the set of misbehaving expression types.
      Parameters:
      info - the expression information object used to collect the information
      Since:
      3.2

    • computeHashCode

      protected int computeHashCode()
      Method to compute the hash code for this object. The result returned from this method in cached in the fHashCode field. If the value returned from the method equals HASH_CODE_NOT_COMPUTED (e.g. -1) then the value is incremented by one.

      This default implementation calls super.hashCode()

      Returns:
      a hash code for this object.
      Since:
      3.2

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object