Move Java Blimp shell code to app subpackage

blimp/client/app/android/java/src/org/chromium/blimp/preferences/PreferencesUtil.java

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package org.chromium.blimp.preferences;
-
-import android.content.Context;
-
-import org.chromium.base.ContextUtils;
-import org.chromium.blimp.R;
-
-/**
- * Provides helper methods for storing and retrieving values in android shared preferences.
- */
-public class PreferencesUtil {
-    /**
-     * Preference that stores the last used assigner URL.
-     */
-    private static final String PREF_LAST_USED_ASSIGNER = "last_known_assigner";
-    private static final String DEFAULT_EMPTY_STRING = "";
-
-    /**
-     * Finds the assigner to be used from user's last preference. If the app is being used for the
-     * first time, the first entry from the assigner array would be used.
-     * @return assigner to use.
-     */
-    public static String findAssignerUrl(Context context) {
-        String lastAssigner = getLastUsedAssigner(context);
-        if (lastAssigner.isEmpty()) {
-            String[] assignerUrls = context.getResources().getStringArray(
-                    R.array.blimp_assigner_urls);
-            assert assignerUrls != null && assignerUrls.length > 0;
-            lastAssigner = assignerUrls[0];
-            setLastUsedAssigner(context, lastAssigner);
-        }
-        return lastAssigner;
-    }
-
-    /**
-     * Reads the last used assigner from shared preference.
-     * @param context The current Android context
-     * @return The saved value of assigner preference
-     */
-    public static String getLastUsedAssigner(Context context) {
-        return readString(context, PREF_LAST_USED_ASSIGNER);
-    }
-
-    /**
-     * Sets the last used assigner.
-     * @param context The current Android context
-     * @param assigner The new value of assigner preference
-     */
-    public static void setLastUsedAssigner(Context context, String assigner) {
-        writeString(context, PREF_LAST_USED_ASSIGNER, assigner);
-    }
-
-    /**
-     * Reads a string value from shared preference.
-     * @param context The current Android context
-     * @param key The name of the preference to read
-     * @return The current value of the preference or a default value
-     */
-    private static String readString(Context context, String key) {
-        return ContextUtils.getAppSharedPreferences().getString(key, DEFAULT_EMPTY_STRING);
-    }
-
-    /**
-     * Writes the given string into shared preference.
-     * @param context The current Android context
-     * @param key The name of the preference to modify
-     * @param value The new value for the preference
-     */
-    private static void writeString(Context context, String key, String value) {
-        ContextUtils.getAppSharedPreferences().edit().putString(key, value).apply();
-    }
-}