1 files changed, 96 insertions, 0 deletions
diff --git a/src/main/java/org/uic/barcode/asn1/datatypes/Optional.java b/src/main/java/org/uic/barcode/asn1/datatypes/Optional.java
new file mode 100644
index 0000000..757ba29
--- /dev/null
+++ b/src/main/java/org/uic/barcode/asn1/datatypes/Optional.java
@@ -0,0 +1,96 @@
+package org.uic.barcode.asn1.datatypes;
+
+import java.util.NoSuchElementException;
+import java.util.Objects;
+
+/** Represents optional values.
+ *
+ * Should be replaced by java.util.Optional from Java 8, when project moves to Java 8.
+ *
+ * @param <T> type of contained elements */
+public class Optional<T> {
+
+    private final T       element;
+    private final boolean isPresent;
+
+    private Optional(T element, boolean isPresent) {
+        this.element = element;
+        this.isPresent = isPresent;
+    }
+
+    /** @return true if the Option contains a value */
+    public boolean isPresent() {
+        return isPresent;
+    }
+
+    /** @return the element if the option is not empty
+     * @throws java.util.NoSuchElementException if the option is empty */
+    public T get() {
+        if (isPresent) {
+            return element;
+        } else {
+            throw new NoSuchElementException("None.get");
+        }
+    }
+
+    /** @return the value, if present, otherwise return {@code other}
+     * @param other the value to be returned if there is no value present */
+    public T orElse(T other) {
+        return isPresent() ? get() : other;
+    }
+
+    /**
+     * Indicates whether some other object is "equal to" this Optional. The
+     * other object is considered equal if:
+     * <ul>
+     * <li>it is also an {@code Optional} and;
+     * <li>both instances have no value present or;
+     * <li>the present values are "equal to" each other via {@code equals()}.
+     * </ul>
+     *
+     * @param obj an object to be tested for equality
+     * @return {code true} if the other object is "equal to" this object
+     * otherwise {@code false}
+     */
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+
+        if (!(obj instanceof Optional)) {
+            return false;
+        }
+
+        Optional<?> other = (Optional<?>) obj;
+        return Objects.equals(element, other.element);
+    }
+
+    /**
+     * Returns the hash code value of the present value, if any, or 0 (zero) if
+     * no value is present.
+     *
+     * @return hash code value of the present value or 0 if no value is present
+     */
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(element);
+    }
+
+    /** Returns an Option containing the value.
+     *
+     * @param <A> the type of the value
+     * @param element contained value
+     * @return a new Option that contains the value */
+    public static <A> Optional<A> of(final A element) {
+        return new Optional<A>(element, true);
+    }
+
+    /** Returns an empty option.
+     *
+     * @param <A>
+     * @return an empty Option */
+    public static <A> Optional<A> empty() {
+        return new Optional<A>(null, false);
+    }
+}