adding ExpaandableEnum to azure-core utils

sdk/core/azure-core/src/main/java/com/azure/android/core/util/ExpandableStringEnum.java

@@ -0,0 +1,122 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+// Code generated by Microsoft (R) AutoRest Code Generator.
+
+package com.azure.android.core.util;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Locale;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+/**
+ * Base implementation for expandable, single string enums.
+ *
+ * @param <T> A specific expandable enum type.
+ */
+public abstract class ExpandableStringEnum<T extends ExpandableStringEnum<T>> {
+    private static final ConcurrentMap<String, ? extends ExpandableStringEnum<?>> VALUES_BY_NAME =
+        new ConcurrentHashMap<>();
+
+    private String name;
+    private Class<T> clazz;
+
+    private static String uniqueKey(Class<?> clazz, String name) {
+        if (clazz != null) {
+            return (clazz.getName() + "#" + name).toLowerCase(Locale.ROOT);
+        } else {
+            throw new IllegalArgumentException();
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    T nameValue(String name, T value, Class<T> clazz) {
+        this.name = name;
+        this.clazz = clazz;
+
+        ((ConcurrentMap<String, T>) VALUES_BY_NAME).put(uniqueKey(clazz, name), value);
+
+        return (T) this;
+    }
+
+    /**
+     * Creates an instance of the specific expandable string enum from a String.
+     *
+     * @param name  The value to create the instance from.
+     * @param clazz The class of the expandable string enum.
+     * @param <T>   The class of the expandable string enum.
+     * @return The expandable string enum instance.
+     */
+    @SuppressWarnings("unchecked")
+    protected static <T extends ExpandableStringEnum<T>> T fromString(String name, Class<T> clazz) {
+        if (name == null) {
+            return null;
+        } else {
+            T value = (T) VALUES_BY_NAME.get(uniqueKey(clazz, name));
+
+            if (value != null) {
+                return value;
+            }
+        }
+
+        try {
+            T value = clazz.newInstance();
+            return value.nameValue(name, value, clazz);
+        } catch (InstantiationException e) {
+            return null;
+        } catch (IllegalAccessException e) {
+            return null;
+        }
+    }
+
+    /**
+     * Gets a collection of all known values to an expandable string enum type.
+     *
+     * @param clazz The class of the expandable string enum.
+     * @param <T>   The class of the expandable string enum.
+     * @return A collection of all known values for the given {@code clazz}.
+     */
+    @SuppressWarnings("unchecked")
+    protected static <T extends ExpandableStringEnum<T>> Collection<T> values(Class<T> clazz) {
+        // Make a copy of all values
+        Collection<? extends ExpandableStringEnum<?>> values = new ArrayList<>(VALUES_BY_NAME.values());
+
+        Collection<T> list = new HashSet<>();
+
+        for (ExpandableStringEnum<?> value : values) {
+            if (value.getClass().isAssignableFrom(clazz)) {
+                list.add((T) value);
+            }
+        }
+
+        return list;
+    }
+
+    @Override
+    public String toString() {
+        return this.name;
+    }
+
+    @Override
+    public int hashCode() {
+        return uniqueKey(this.clazz, this.name).hashCode();
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == null) {
+            return false;
+        } else if (clazz == null || !clazz.isAssignableFrom(obj.getClass())) {
+            return false;
+        } else if (obj == this) {
+            return true;
+        } else if (this.name == null) {
+            return ((ExpandableStringEnum<T>) obj).name == null;
+        } else {
+            return this.name.equals(((ExpandableStringEnum<T>) obj).name);
+        }
+    }
+}