Package org.geotools.util

Class ClassChanger<S extends Comparable<S>,​T extends Number>

  • public abstract class ClassChanger<S extends Comparable<S>,​T extends Number>
extends Object
    A central place to register transformations between an arbitrary class and a Number. For example, it is sometime convenient to consider Date objects as if they were Long objects for computation purpose in generic algorithms. Client can call the following method to convert an arbitrary object to a Number: 
     Object someArbitraryObject = new Date();
 Number myObjectAsANumber = ClassChanger.toNumber(someArbitraryObject);
    Since:
    2.0
    Author:
    Martin Desruisseaux (IRD)

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      protected ClassChanger​(Class<S> source, Class<T> target)
      Constructs a new class changer.

    • Method Summary

      All Methods Static Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      static <N extends Number>
      N      		 cast​(Number n, Class<N> c)
      Casts the number to the specified class.
      protected abstract T convert​(S object)
      Returns the numerical value for an object.
      static Class<? extends Number> getFinestClass​(double value)
      Returns the smallest class capable to hold the specified value.
      static Class<? extends Number> getFinestClass​(Class<? extends Number> c1, Class<? extends Number> c2)
      Returns the class of the finest type.
      static Class<?> getTransformedClass​(Class<?> source)
      Returns the target class for the specified source class, if a suitable transformation is known.
      static Class<? extends Number> getWidestClass​(Class<? extends Number> c1, Class<? extends Number> c2)
      Returns the class of the widest type.
      static Class<? extends Number> getWidestClass​(Number n1, Number n2)
      Returns the class of the widest type.
      protected abstract S inverseConvert​(T value)
      Returns an instance of the converted classe from a numerical value.
      static void register​(ClassChanger<?,​?> converter)
      Registers a new converter.
      static <C extends Comparable>
      C      		 toComparable​(Number value, Class<C> classe)
      Wraps the specified number as an instance of the specified classe.
      static <K> K toNumber​(Comparable<K> object)
      Returns the numeric value for the specified object.
      static Class<?> toPrimitive​(Class<?> c)
      Converts a wrapper class to a primitive class.
      String toString()
      Returns a string representation for this class changer.
      static Class<?> toWrapper​(Class<?> c)
      Converts a primitive class to a wrapper class.

      • Methods inherited from class Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

    • Constructor Detail

      • ClassChanger

        protected ClassChanger​(Class<S> source,
                       Class<T> target)
        Constructs a new class changer.
        Parameters:
        source - Parent class for convert(S)'s input objects.
        target - Parent class for convert(S)'s output objects.

    • Method Detail

      • convert

        protected abstract T convert​(S object)
                      throws ClassCastException
        Returns the numerical value for an object.
        Parameters:
        object - Object to convert (may be null).
        Returns:
        The object's numerical value.
        Throws:
        ClassCastException - if object is not of the expected class.

      • inverseConvert

        protected abstract S inverseConvert​(T value)
        Returns an instance of the converted classe from a numerical value.
        Parameters:
        value - The value to wrap.
        Returns:
        An instance of the source classe.

      • toString

        public String toString()
        Returns a string representation for this class changer.
        Overrides:
        toString in class Object

      • register

        public static void register​(ClassChanger<?,​?> converter)
                     throws IllegalStateException
        Registers a new converter. All registered ClassChanger will be taken in account by the toNumber(java.lang.Comparable<K>) method. The example below register a conversion for the Date class: 
          ClassChanger.register(new ClassChanger(Date.class, Long.class) {
      protected Long convert(final Comparable o) {
          return ((Date) o).getTime();
      }
  
      protected Comparable inverseConvert(final Number number) {
          return new Date(number.longValue());
      }
  });
        Parameters:
        converter - The ClassChanger to add.
        Throws:
        IllegalStateException - if an other ClassChanger was already registered for the same source class. This is usually not a concern since the registration usually take place during the class initialization ("static" constructor).

      • getTransformedClass

        public static Class<?> getTransformedClass​(Class<?> source)
        Returns the target class for the specified source class, if a suitable transformation is known. The source class is a Comparable subclass that will be specified as input to convert(S). The target class is a Number subclass that will be returned as output by convert(S). If no suitable mapping is found, then source is returned.

      • toNumber

        public static <K> K toNumber​(Comparable<K> object)
                      throws ClassNotFoundException
        Returns the numeric value for the specified object. For example the code toNumber(new Date()) returns the Date.getTime() value of the specified date object as a Long.
        Parameters:
        object - Object to convert (may be null).
        Returns:
        null if object was null; otherwise object if the supplied object is already an instance of Number; otherwise a new number with the numerical value.
        Throws:
        ClassNotFoundException - if object is not an instance of a registered class.

      • toComparable

        public static <C extends Comparable> C toComparable​(Number value,
                                                    Class<C> classe)
                                             throws ClassNotFoundException
        Wraps the specified number as an instance of the specified classe. For example toComparable(new Long(time), Date.class) is equivalent to new Date(time). There is of course no point to use this method if the destination class is know at compile time. This method is useful for creating instance of classes choosen dynamically at run time.
        Parameters:
        value - The numerical value (may be null).
        classe - The desired classe for return value.
        Throws:
        ClassNotFoundException - if classe is not a registered class.

      • toPrimitive

        public static Class<?> toPrimitive​(Class<?> c)
                            throws IllegalArgumentException
        Converts a wrapper class to a primitive class. For example this method converts Double.class to Double.TYPE.
        Parameters:
        c - The wrapper class.
        Returns:
        The primitive class.
        Throws:
        IllegalArgumentException - if the specified class is not a wrapper for a primitive.

      • toWrapper

        public static Class<?> toWrapper​(Class<?> c)
                          throws IllegalArgumentException
        Converts a primitive class to a wrapper class. For example this method converts Double.TYPE to Double.class.
        Parameters:
        c - The primitive class.
        Returns:
        The wrapper class.
        Throws:
        IllegalArgumentException - if the specified class is not a primitive.

      • cast

        public static <N extends Number> N cast​(Number n,
                                        Class<N> c)
                                 throws IllegalArgumentException
        Casts the number to the specified class. The class must by one of Byte, Short, Integer, Long, Float or Double.
        Throws:
        IllegalArgumentException

      • getWidestClass

        public static Class<? extends Number> getWidestClass​(Number n1,
                                                     Number n2)
                                              throws IllegalArgumentException
        Returns the class of the widest type. Numbers n1 and n2 must be instance of any of Byte, Short, Integer, Long, Float or Double types. At most one of the argument can be null.
        Throws:
        IllegalArgumentException

      • getWidestClass

        public static Class<? extends Number> getWidestClass​(Class<? extends Number> c1,
                                                     Class<? extends Number> c2)
                                              throws IllegalArgumentException
        Returns the class of the widest type. Classes c1 and c2 must be of any of Byte, Short, Integer, Long, Float or Double types. At most one of the argument can be null.
        Throws:
        IllegalArgumentException

      • getFinestClass

        public static Class<? extends Number> getFinestClass​(Class<? extends Number> c1,
                                                     Class<? extends Number> c2)
                                              throws IllegalArgumentException
        Returns the class of the finest type. Classes c1 and c2 must be of any of Byte, Short, Integer, Long, Float or Double types. At most one of the argument can be null.
        Throws:
        IllegalArgumentException

      • getFinestClass

        public static Class<? extends Number> getFinestClass​(double value)
        Returns the smallest class capable to hold the specified value.