android tool: support --target symbolic target names

BUG 2056746

Change-Id: I579e58f7c63cf404cd11af394f41ed7f998593ce

tools/sdkmanager/libs/sdklib/src/com/android/sdklib/SdkManager.java

@@ -88,6 +88,16 @@ public final class SdkManager {
     private final String mSdkLocation;
     private IAndroidTarget[] mTargets;
 
+    /**
+     * Create a new {@link SdkManager} instance.
+     * External users should use {@link #createManager(String, ISdkLog)}.
+     *
+     * @param sdkLocation the location of the SDK.
+     */
+    private SdkManager(String sdkLocation) {
+        mSdkLocation = sdkLocation;
+    }
+
     /**
      * Creates an {@link SdkManager} for a given sdk location.
      * @param sdkLocation the location of the SDK.
@@ -125,11 +135,23 @@ public final class SdkManager {
 
     /**
      * Returns the targets that are available in the SDK.
+     * <p/>
+     * The array can be empty but not null.
      */
     public IAndroidTarget[] getTargets() {
         return mTargets;
     }
 
+    /**
+     * Sets the targets that are available in the SDK.
+     * <p/>
+     * The array can be empty but not null.
+     */
+    private void setTargets(IAndroidTarget[] targets) {
+        assert targets != null;
+        mTargets = targets;
+    }
+
     /**
      * Returns a target from a hash that was generated by {@link IAndroidTarget#hashString()}.
      *
@@ -202,14 +224,6 @@ public final class SdkManager {
         setTargets(list.toArray(new IAndroidTarget[list.size()]));
     }
 
-    private SdkManager(String sdkLocation) {
-        mSdkLocation = sdkLocation;
-    }
-
-    private void setTargets(IAndroidTarget[] targets) {
-        mTargets = targets;
-    }
-
     /**
      * Loads the Platforms from the SDK.
      * @param location Location of the SDK