ezvcard.util

Class CaseClasses<T,V>

java.lang.Object

ezvcard.util.CaseClasses<T,V>

Type Parameters:

T - the case class

V - the value that the class holds (e.g. String)

Direct Known Subclasses:

MediaTypeCaseClasses, VCardParameterCaseClasses

public abstract class CaseClasses<T,V>
extends Object

Manages objects that are like enums in that they are constant, but unlike enums in that new instances can be created during runtime. This class ensures that all instances of a class are unique, so they can be safely compared using "==" (provided their constructors are private).

This class awkwardly mimics the "case class" feature in Scala.

Example:

 public class Color {
   public static final CaseClasses<Color, String> VALUES = new ColorCaseClasses();
   public static final Color RED = new Color("red");
   public static final Color GREEN = new Color("green");
   public static final Color BLUE = new Color("blue");
 
   private final String name;
 
   // Constructor should be PRIVATE in order to prevent users from
   // instantiating their own objects and circumventing the CaseClasses
   // object.
   private Color(String name) {
     this.name = name;
   }
 
   public String getName() {
     return name;
   }
 
   // CaseClasses implementation is an inner class because the Color
   // constructor is private.
   private static class ColorCaseClasses extends CaseClasses<Color, String> {
     public ColorCaseClasses() {
       super(Color.class);
     }
 
     @Override
     protected Color create(String value) {
       return new Color(value);
     }
 
     @Override
     protected boolean matches(Color object, String value) {
       return object.getName().equalsIgnoreCase(value);
     }
   }
 }
 
 public class Test {
   @Test
   public void test() {
     assertTrue(Color.RED == Color.VALUES.find("Red"));
     assertTrue(Color.RED == Color.VALUES.get("Red"));
 
     assertNull(Color.VALUES.find("purple"));
     Color purple = Color.VALUES.get("purple");
     assertEquals("purple", purple.getName());
     assertTrue(purple == Color.VALUES.get("Purple"));
   }
 }
 

Author:

Michael Angstadt

Field Summary

Fields

Modifier and Type	Field and Description
protected Class<T>	clazz

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	CaseClasses(Class<T> clazz) Creates a new case class collection.

Method Summary

Modifier and Type	Method and Description
Collection<T>	all() Gets all the static constants of the case class (does not include runtime-defined constants).
protected abstract T	create(V value) Creates a new instance of the case class.
T	find(V value) Searches for a case object by value, only looking at the case class' static constants (does not search runtime-defined constants).
T	get(V value) Searches for a case object by value, creating a new object if one cannot be found.
protected abstract boolean	matches(T object, V value) Determines if a case object is "equal to" the given value.

Methods inherited from class java.lang.Object

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

Field Detail

clazz

protected final Class<T> clazz

Constructor Detail

CaseClasses

protected CaseClasses(Class<T> clazz)

Creates a new case class collection.

Parameters:

clazz - the case class

Method Detail

create

protected abstract T create(V value)

Creates a new instance of the case class.

Parameters:

value - the value to give the instance

Returns:

the new instance

matches

protected abstract boolean matches(T object,
                                   V value)

Determines if a case object is "equal to" the given value.

Parameters:

object - the case object

value - the value

Returns:

true if it matches, false if not

find

public T find(V value)

Searches for a case object by value, only looking at the case class' static constants (does not search runtime-defined constants).

Parameters:

value - the value

Returns:

the object or null if one wasn't found

get

public T get(V value)

Searches for a case object by value, creating a new object if one cannot be found.

Parameters:

value - the value

Returns:

the object

all

public Collection<T> all()

Gets all the static constants of the case class (does not include runtime-defined constants).

Returns:

all static constants