org.argeo.api.uuid/src/org/argeo/api/uuid/UuidHolder.java

   1 package org.argeo.api.uuid;
   2
   3 import java.io.Serializable;
   4 import java.util.Objects;
   5 import java.util.UUID;
   6 import java.util.function.Supplier;
   7
   8 /**
   9  * An immutable wrapper for an {@link UUID}, which can be used as a base for a
  10  * derivation hierarchy, while strongly enforcing semantic equality with the
  11  * underlying {@link UUID}. It is therefore immutable, and all base methods are
  12  * directly and trivially based on {@link UUID} methods; they do represent the
  13  * same unique "thing" (be it an entity, a point in time, etc.), consistently
  14  * with the fundamental concept of uuid.
  15  */
  16 public class UuidHolder implements Supplier<UUID>, Serializable {
  17         private static final long serialVersionUID = APM.SERIAL;
  18
  19         /**
  20          * The wrapped {@link UUID}. Protected rather than private, since it is
  21          * immutable and a {@link UUID} is itself immutable.
  22          */
  23         protected final UUID uuid;
  24
  25         /**
  26          * Constructs a new {@link UuidHolder} based on this uuid.
  27          *
  28          * @param uuid the UUID to wrap, cannot be null.
  29          * @throws NullPointerException if the provided uuid is null.
  30          */
  31         protected UuidHolder(UUID uuid) {
  32                 Objects.requireNonNull(uuid, "UUID cannot be null");
  33                 this.uuid = uuid;
  34         }
  35
  36         /** The wrapped {@link UUID}. */
  37         public final UUID getUuid() {
  38                 return uuid;
  39         }
  40
  41         /** The wrapped {@link UUID}. */
  42         @Override
  43         public final UUID get() {
  44                 return getUuid();
  45         }
  46
  47         /** Calls {@link UUID#hashCode()} on the wrapped {@link UUID}. */
  48         @Override
  49         public final int hashCode() {
  50                 return uuid.hashCode();
  51         }
  52
  53         /**
  54          * Equals only with non-null {@link UuidHolder} if and only if their wrapped
  55          * uuid are equals by calling {@link UUID#equals(Object)}.
  56          */
  57         @Override
  58         public final boolean equals(Object obj) {
  59                 if (obj == null || !(obj instanceof UuidHolder))
  60                         return false;
  61                 UuidHolder typedUuid = (UuidHolder) obj;
  62                 return uuid.equals(typedUuid.uuid);
  63         }
  64
  65         /** Calls {@link UUID#toString()} on the wrapped {@link UUID}. */
  66         @Override
  67         public final String toString() {
  68                 return uuid.toString();
  69         }
  70
  71 }