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Android example source code file (SparseBooleanArray.java)

This example Android source code file (SparseBooleanArray.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, fail, runtimeexception, sparsebooleanarray, util, utilities, utils

The SparseBooleanArray.java Android example source code

/*
 * Copyright (C) 2006 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 android.util;

import com.android.internal.util.ArrayUtils;

/**
 * SparseBooleanArrays map integers to booleans.
 * Unlike a normal array of booleans
 * there can be gaps in the indices.  It is intended to be more efficient
 * than using a HashMap to map Integers to Booleans.
 */
public class SparseBooleanArray {
    /**
     * Creates a new SparseBooleanArray containing no mappings.
     */
    public SparseBooleanArray() {
        this(10);
    }

    /**
     * Creates a new SparseBooleanArray containing no mappings that will not
     * require any additional memory allocation to store the specified
     * number of mappings.
     */
    public SparseBooleanArray(int initialCapacity) {
        initialCapacity = ArrayUtils.idealIntArraySize(initialCapacity);

        mKeys = new int[initialCapacity];
        mValues = new boolean[initialCapacity];
        mSize = 0;
    }

    /**
     * Gets the boolean mapped from the specified key, or <code>false
     * if no such mapping has been made.
     */
    public boolean get(int key) {
        return get(key, false);
    }

    /**
     * Gets the boolean mapped from the specified key, or the specified value
     * if no such mapping has been made.
     */
    public boolean get(int key, boolean valueIfKeyNotFound) {
        int i = binarySearch(mKeys, 0, mSize, key);

        if (i < 0) {
            return valueIfKeyNotFound;
        } else {
            return mValues[i];
        }
    }

    /**
     * Removes the mapping from the specified key, if there was any.
     */
    public void delete(int key) {
        int i = binarySearch(mKeys, 0, mSize, key);

        if (i >= 0) {
            System.arraycopy(mKeys, i + 1, mKeys, i, mSize - (i + 1));
            System.arraycopy(mValues, i + 1, mValues, i, mSize - (i + 1));
            mSize--;
        }
    }

    /**
     * Adds a mapping from the specified key to the specified value,
     * replacing the previous mapping from the specified key if there
     * was one.
     */
    public void put(int key, boolean value) {
        int i = binarySearch(mKeys, 0, mSize, key);

        if (i >= 0) {
            mValues[i] = value;
        } else {
            i = ~i;

            if (mSize >= mKeys.length) {
                int n = ArrayUtils.idealIntArraySize(mSize + 1);

                int[] nkeys = new int[n];
                boolean[] nvalues = new boolean[n];

                // Log.e("SparseBooleanArray", "grow " + mKeys.length + " to " + n);
                System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length);
                System.arraycopy(mValues, 0, nvalues, 0, mValues.length);

                mKeys = nkeys;
                mValues = nvalues;
            }

            if (mSize - i != 0) {
                // Log.e("SparseBooleanArray", "move " + (mSize - i));
                System.arraycopy(mKeys, i, mKeys, i + 1, mSize - i);
                System.arraycopy(mValues, i, mValues, i + 1, mSize - i);
            }

            mKeys[i] = key;
            mValues[i] = value;
            mSize++;
        }
    }

    /**
     * Returns the number of key-value mappings that this SparseBooleanArray
     * currently stores.
     */
    public int size() {
        return mSize;
    }

    /**
     * Given an index in the range <code>0...size()-1, returns
     * the key from the <code>indexth key-value mapping that this
     * SparseBooleanArray stores.  
     */
    public int keyAt(int index) {
        return mKeys[index];
    }
    
    /**
     * Given an index in the range <code>0...size()-1, returns
     * the value from the <code>indexth key-value mapping that this
     * SparseBooleanArray stores.  
     */
    public boolean valueAt(int index) {
        return mValues[index];
    }

    /**
     * Returns the index for which {@link #keyAt} would return the
     * specified key, or a negative number if the specified
     * key is not mapped.
     */
    public int indexOfKey(int key) {
        return binarySearch(mKeys, 0, mSize, key);
    }

    /**
     * Returns an index for which {@link #valueAt} would return the
     * specified key, or a negative number if no keys map to the
     * specified value.
     * Beware that this is a linear search, unlike lookups by key,
     * and that multiple keys can map to the same value and this will
     * find only one of them.
     */
    public int indexOfValue(boolean value) {
        for (int i = 0; i < mSize; i++)
            if (mValues[i] == value)
                return i;

        return -1;
    }

    /**
     * Removes all key-value mappings from this SparseBooleanArray.
     */
    public void clear() {
        mSize = 0;
    }

    /**
     * Puts a key/value pair into the array, optimizing for the case where
     * the key is greater than all existing keys in the array.
     */
    public void append(int key, boolean value) {
        if (mSize != 0 && key <= mKeys[mSize - 1]) {
            put(key, value);
            return;
        }

        int pos = mSize;
        if (pos >= mKeys.length) {
            int n = ArrayUtils.idealIntArraySize(pos + 1);

            int[] nkeys = new int[n];
            boolean[] nvalues = new boolean[n];

            // Log.e("SparseBooleanArray", "grow " + mKeys.length + " to " + n);
            System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length);
            System.arraycopy(mValues, 0, nvalues, 0, mValues.length);

            mKeys = nkeys;
            mValues = nvalues;
        }

        mKeys[pos] = key;
        mValues[pos] = value;
        mSize = pos + 1;
    }
    
    private static int binarySearch(int[] a, int start, int len, int key) {
        int high = start + len, low = start - 1, guess;

        while (high - low > 1) {
            guess = (high + low) / 2;

            if (a[guess] < key)
                low = guess;
            else
                high = guess;
        }

        if (high == start + len)
            return ~(start + len);
        else if (a[high] == key)
            return high;
        else
            return ~high;
    }

    private void checkIntegrity() {
        for (int i = 1; i < mSize; i++) {
            if (mKeys[i] <= mKeys[i - 1]) {
                for (int j = 0; j < mSize; j++) {
                    Log.e("FAIL", j + ": " + mKeys[j] + " -> " + mValues[j]);
                }

                throw new RuntimeException();
            }
        }
    }

    private int[] mKeys;
    private boolean[] mValues;
    private int mSize;
}

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