Created enum Region.java to retrieve Regions without doing request.

google-cloud-clients/google-cloud-compute/src/main/java/com/google/cloud/compute/Region.java

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+/*
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.cloud.compute;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Enumeration of Regions.
+ *
+ * @see <a href="https://cloud.google.com/compute/docs/regions-zones/">Regions and Zones</a>
+ */
+public enum Region {
+  ASIA_EAST1("asia-east1", new String[] {"asia-east1-a", "asia-east1-b", "asia-east1-c"}),
+  ASIA_EAST2("asia-east2", new String[] {"asia-east2-a", "asia-east2-b", "asia-east2-c"}),
+  ASIA_NORTHEAST1(
+      "asia-northeast1",
+      new String[] {"asia-northeast1-a", "asia-northeast1-b", "asia-northeast1-c"}),
+  ASIA_SOUTH1("asia-south1", new String[] {"asia-south1-a", "asia-south1-b", "asia-south1-c"}),
+  ASIA_SOUTHEAST1(
+      "asia-southeast1",
+      new String[] {"asia-southeast1-a", "asia-southeast1-b", "asia-southeast1-c"}),
+  AUSTRALIA_SOUTHEAST1(
+      "australia-southeast1",
+      new String[] {"australia-southeast1-a", "australia-southeast1-b", "australia-southeast1-c"}),
+  EUROPE_NORTH1(
+      "europe-north1", new String[] {"europe-north1-a", "europe-north1-b", "europe-north1-c"}),
+  EUROPE_WEST1("europe-west1", new String[] {"europe-west1-b", "europe-west1-c", "europe-west1-d"}),
+  EUROPE_WEST2("europe-west2", new String[] {"europe-west2-a", "europe-west2-b", "europe-west2-c"}),
+  EUROPE_WEST3("europe-west3", new String[] {"europe-west3-a", "europe-west3-b", "europe-west3-c"}),
+  EUROPE_WEST4("europe-west4", new String[] {"europe-west4-a", "europe-west4-b", "europe-west4-c"}),
+  NORTHAMERICA_NORTHEAST1(
+      "northamerica-northeast1",
+      new String[] {
+        "northamerica-northeast1-a", "northamerica-northeast1-b", "northamerica-northeast1-c"
+      }),
+  SOUTHAMERICA_EAST1(
+      "southamerica-east1",
+      new String[] {"southamerica-east1-a", "southamerica-east1-b", "southamerica-east1-c"}),
+  US_CENTRAL1(
+      "us-central1",
+      new String[] {"us-central1-a", "us-central1-b", "us-central1-c", "us-central1-f"}),
+  US_EAST1("us-east1", new String[] {"us-east1-b", "us-east1-c", "us-east1-d"}),
+  US_EAST4("us-east4", new String[] {"us-east4-a", "us-east4-b", "us-east4-c"}),
+  US_WEST1("us-west1", new String[] {"us-west1-a", "us-west1-b", "us-west1-c"}),
+  US_WEST2("us-west2", new String[] {"us-west2-a", "us-west2-b", "us-west2-c"});
+
+  private static final Map<String, Region> REGIONS = new HashMap<>();
+
+  static {
+    for (Region region : Region.values()) {
+      REGIONS.put(region.name, region);
+    }
+  }
+
+  private final String name;
+  private final String[] zones;
+
+  private Region(String name, String[] zones) {
+    this.name = name;
+    this.zones = zones;
+  }
+
+  /** The name of this region. */
+  public String getName() {
+    return name;
+  }
+
+  /** The zones of this region. */
+  public String[] getZones() {
+    return zones;
+  }
+
+  /**
+   * Returns a region enum corresponding to the given region name.
+   *
+   * @param regionName The name of the region.
+   * @return Region enum representing the given region name, or a null if there is no Region enum
+   *     that is representing the given region name.
+   */
+  public static Region fromName(String regionName) {
+    return REGIONS.get(regionName);
+  }
+}

google-cloud-clients/google-cloud-compute/src/test/java/com/google/cloud/compute/RegionTest.java

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+/*
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.cloud.compute;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class RegionTest {
+  @Test
+  public void fromNameWhenNullReturnNull() {
+    Assert.assertNull(Region.fromName(null));
+  }
+
+  @Test
+  public void fromNameWhenEmptyReturnNull() {
+    Assert.assertNull(Region.fromName(""));
+  }
+
+  @Test
+  public void fromNameWhenInvalidReturnNull() {
+    Assert.assertNull(Region.fromName("mars"));
+  }
+
+  @Test
+  public void fromNameWhenValidReturnRegion() {
+    Assert.assertEquals(Region.ASIA_EAST1, Region.fromName("asia-east1"));
+  }
+}