Android example source code file (Dictionary.java)

This example Android source code file (Dictionary.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, arraylist, bufferedreader, concurrenthashmap, content, dictionary, inputstreamreader, io, ioexception, list, map, resources, runnable, runtimeexception, string, text, thread, util, utilities, word

The Dictionary.java Android example source code

/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * 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
 *
 *      http://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.example.android.searchabledict;

import android.content.res.Resources;
import android.text.TextUtils;
import android.util.Log;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Contains logic to load the word of words and definitions and find a list of matching words
 * given a query.  Everything is held in memory; this is not a robust way to serve lots of
 * words and is only for demo purposes.
 *
 * You may want to consider using an SQLite database. In practice, you'll want to make sure your
 * suggestion provider is as efficient as possible, as the system will be taxed while performing
 * searches across many sources for each keystroke the user enters into Quick Search Box.
 */
public class Dictionary {

    public static class Word {
        public final String word;
        public final String definition;

        public Word(String word, String definition) {
            this.word = word;
            this.definition = definition;
        }
    }

    private static final Dictionary sInstance = new Dictionary();

    public static Dictionary getInstance() {
        return sInstance;
    }

    private final Map<String, List mDict = new ConcurrentHashMap>();

    private Dictionary() {
    }

    private boolean mLoaded = false;

    /**
     * Loads the words and definitions if they haven't been loaded already.
     *
     * @param resources Used to load the file containing the words and definitions.
     */
    public synchronized void ensureLoaded(final Resources resources) {
        if (mLoaded) return;

        new Thread(new Runnable() {
            public void run() {
                try {
                    loadWords(resources);
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }).start();
    }

    private synchronized void loadWords(Resources resources) throws IOException {
        if (mLoaded) return;

        Log.d("dict", "loading words");
        InputStream inputStream = resources.openRawResource(R.raw.definitions);
        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

        try {
            String line;
            while((line = reader.readLine()) != null) {
                String[] strings = TextUtils.split(line, "-");
                if (strings.length < 2) continue;
                addWord(strings[0].trim(), strings[1].trim());
            }
        } finally {
            reader.close();
        }
        mLoaded = true;
    }


    public List<Word> getMatches(String query) {
        List<Word> list = mDict.get(query);
        return list == null ? Collections.EMPTY_LIST : list;
    }

    private void addWord(String word, String definition) {
        final Word theWord = new Word(word, definition);

        final int len = word.length();
        for (int i = 0; i < len; i++) {
            final String prefix = word.substring(0, len - i);
            addMatch(prefix, theWord);
        }
    }

    private void addMatch(String query, Word word) {
        List<Word> matches = mDict.get(query);
        if (matches == null) {
            matches = new ArrayList<Word>();
            mDict.put(query, matches);
        }
        matches.add(word);
    }
}