1 package uk.org.lidalia.lang;
2
3 import static com.google.common.base.Preconditions.checkNotNull;
4 import static uk.org.lidalia.lang.Classes.inSameClassHierarchy;
5
6 /**
7 * Convenience class for types that represent a higher level abstraction over a single lower level type; for instance
8 * a class representing a network Port might extend {@code WrappedValue} and pass an {@code java.lang.Integer} as the value.
9 *
10 * Provides implementations of {@link #equals(Object)}, {@link #toString()} and {@link #hashCode()} based on the value
11 * of the wrapped instance.
12 */
13 public abstract class WrappedValue {
14
15 private final Object wrapped;
16
17 protected WrappedValue(final Object wrapped) {
18 this.wrapped = checkNotNull(wrapped);
19 }
20
21 /**
22 * @return the toString representation of the wrapped instance
23 */
24 @Override
25 public String toString() {
26 return wrapped.toString();
27 }
28
29 /**
30 * Applies equality rules based on the value of the wrapped object.
31 * <ul>
32 * <li> normal rules in {@link Object#equals(Object)} - not equal to null, equal to same instance
33 * <li> other's runtime class must be the same, a super or a sub type of the runtime class of this instance
34 * <li> the value of the wrapped instance is the same as the value of the other's wrapped instance
35 * </ul>
36 * @param other the object to compare against
37 * @return true if the other type is logically equal to this
38 */
39 @Override
40 public final boolean equals(final Object other) {
41 if (this == other) return true;
42 if (other == null) return false;
43 if (!(other instanceof WrappedValue) || !inSameClassHierarchy(getClass(), other.getClass())) return false;
44
45 final WrappedValue that = (WrappedValue) other;
46
47 return wrapped.equals(that.wrapped);
48 }
49
50 /**
51 * @return the hashCode of the wrapped instance
52 */
53 @Override
54 public final int hashCode() {
55 return wrapped.hashCode();
56 }
57 }