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SparseArray.javaAPI DocAndroid 1.5 API9020Wed May 06 22:41:56 BST 2009android.util

SparseArray

public class SparseArray extends Object
SparseArrays map integers to Objects. Unlike a normal array of Objects, there can be gaps in the indices. It is intended to be more efficient than using a HashMap to map Integers to Objects.

Fields Summary
private static final Object
DELETED
private boolean
mGarbage
private int[]
mKeys
private Object[]
mValues
private int
mSize
Constructors Summary
public SparseArray()
Creates a new SparseArray containing no mappings.


                
      
        this(10);
public SparseArray(int initialCapacity)
Creates a new SparseArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings.

        initialCapacity = ArrayUtils.idealIntArraySize(initialCapacity);

        mKeys = new int[initialCapacity];
        mValues = new Object[initialCapacity];
        mSize = 0;
Methods Summary
public voidappend(int key, E value)
Puts a key/value pair into the array, optimizing for the case where the key is greater than all existing keys in the array.

        if (mSize != 0 && key <= mKeys[mSize - 1]) {
            put(key, value);
            return;
        }

        if (mGarbage && mSize >= mKeys.length) {
            gc();
        }

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

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

            // Log.e("SparseArray", "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 intbinarySearch(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 voidcheckIntegrity()

        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();
            }
        }
public voidclear()
Removes all key-value mappings from this SparseArray.

        int n = mSize;
        Object[] values = mValues;

        for (int i = 0; i < n; i++) {
            values[i] = null;
        }

        mSize = 0;
        mGarbage = false;
public voiddelete(int key)
Removes the mapping from the specified key, if there was any.

        int i = binarySearch(mKeys, 0, mSize, key);

        if (i >= 0) {
            if (mValues[i] != DELETED) {
                mValues[i] = DELETED;
                mGarbage = true;
            }
        }
private voidgc()

        // Log.e("SparseArray", "gc start with " + mSize);

        int n = mSize;
        int o = 0;
        int[] keys = mKeys;
        Object[] values = mValues;

        for (int i = 0; i < n; i++) {
            Object val = values[i];

            if (val != DELETED) {
                if (i != o) {
                    keys[o] = keys[i];
                    values[o] = val;
                }

                o++;
            }
        }

        mGarbage = false;
        mSize = o;

        // Log.e("SparseArray", "gc end with " + mSize);
public Eget(int key)
Gets the Object mapped from the specified key, or null if no such mapping has been made.

        return get(key, null);
public Eget(int key, E valueIfKeyNotFound)
Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made.

        int i = binarySearch(mKeys, 0, mSize, key);

        if (i < 0 || mValues[i] == DELETED) {
            return valueIfKeyNotFound;
        } else {
            return (E) mValues[i];
        }
public intindexOfKey(int key)
Returns the index for which {@link #keyAt} would return the specified key, or a negative number if the specified key is not mapped.

        if (mGarbage) {
            gc();
        }

        return binarySearch(mKeys, 0, mSize, key);
public intindexOfValue(E value)
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.

        if (mGarbage) {
            gc();
        }

        for (int i = 0; i < mSize; i++)
            if (mValues[i] == value)
                return i;

        return -1;
public intkeyAt(int index)
Given an index in the range 0...size()-1, returns the key from the indexth key-value mapping that this SparseArray stores.

        if (mGarbage) {
            gc();
        }

        return mKeys[index];
public voidput(int key, E value)
Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one.

        int i = binarySearch(mKeys, 0, mSize, key);

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

            if (i < mSize && mValues[i] == DELETED) {
                mKeys[i] = key;
                mValues[i] = value;
                return;
            }

            if (mGarbage && mSize >= mKeys.length) {
                gc();

                // Search again because indices may have changed.
                i = ~binarySearch(mKeys, 0, mSize, key);
            }

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

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

                // Log.e("SparseArray", "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("SparseArray", "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++;
        }
public voidremove(int key)
Alias for {@link #delete(int)}.

        delete(key);
public voidsetValueAt(int index, E value)
Given an index in the range 0...size()-1, sets a new value for the indexth key-value mapping that this SparseArray stores.

        if (mGarbage) {
            gc();
        }

        mValues[index] = value;
public intsize()
Returns the number of key-value mappings that this SparseArray currently stores.

        if (mGarbage) {
            gc();
        }

        return mSize;
public EvalueAt(int index)
Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this SparseArray stores.

        if (mGarbage) {
            gc();
        }

        return (E) mValues[index];