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SparseBooleanArray.javaAPI DocAndroid 5.1 API8663Thu Mar 12 22:22:10 GMT 2015android.util

SparseBooleanArray

public class SparseBooleanArray extends Object implements Cloneable
SparseBooleanArrays map integers to booleans. Unlike a normal array of booleans there can be gaps in the indices. It is intended to be more memory efficient than using a HashMap to map Integers to Booleans, both because it avoids auto-boxing keys and values and its data structure doesn't rely on an extra entry object for each mapping.

Note that this container keeps its mappings in an array data structure, using a binary search to find keys. The implementation is not intended to be appropriate for data structures that may contain large numbers of items. It is generally slower than a traditional HashMap, since lookups require a binary search and adds and removes require inserting and deleting entries in the array. For containers holding up to hundreds of items, the performance difference is not significant, less than 50%.

It is possible to iterate over the items in this container using {@link #keyAt(int)} and {@link #valueAt(int)}. Iterating over the keys using keyAt(int) with ascending values of the index will return the keys in ascending order, or the values corresponding to the keys in ascending order in the case of valueAt(int).

Fields Summary
private int[]
mKeys
private boolean[]
mValues
private int
mSize
Constructors Summary
public SparseBooleanArray()
Creates a new SparseBooleanArray containing no mappings.

        this(10);
public SparseBooleanArray(int initialCapacity)
Creates a new SparseBooleanArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings. If you supply an initial capacity of 0, the sparse array will be initialized with a light-weight representation not requiring any additional array allocations.

        if (initialCapacity == 0) {
            mKeys = EmptyArray.INT;
            mValues = EmptyArray.BOOLEAN;
        } else {
            mKeys = ArrayUtils.newUnpaddedIntArray(initialCapacity);
            mValues = new boolean[mKeys.length];
        }
        mSize = 0;
Methods Summary
public voidappend(int key, boolean 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;
        }

        mKeys = GrowingArrayUtils.append(mKeys, mSize, key);
        mValues = GrowingArrayUtils.append(mValues, mSize, value);
        mSize++;
public voidclear()
Removes all key-value mappings from this SparseBooleanArray.

        mSize = 0;
public android.util.SparseBooleanArrayclone()

        SparseBooleanArray clone = null;
        try {
            clone = (SparseBooleanArray) super.clone();
            clone.mKeys = mKeys.clone();
            clone.mValues = mValues.clone();
        } catch (CloneNotSupportedException cnse) {
            /* ignore */
        }
        return clone;
public voiddelete(int key)
Removes the mapping from the specified key, if there was any.

        int i = ContainerHelpers.binarySearch(mKeys, 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--;
        }
public booleanget(int key)
Gets the boolean mapped from the specified key, or false if no such mapping has been made.

        return get(key, false);
public booleanget(int key, boolean valueIfKeyNotFound)
Gets the boolean mapped from the specified key, or the specified value if no such mapping has been made.

        int i = ContainerHelpers.binarySearch(mKeys, mSize, key);

        if (i < 0) {
            return valueIfKeyNotFound;
        } else {
            return 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.

        return ContainerHelpers.binarySearch(mKeys, mSize, key);
public intindexOfValue(boolean 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.

        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 SparseBooleanArray stores.

The keys corresponding to indices in ascending order are guaranteed to be in ascending order, e.g., keyAt(0) will return the smallest key and keyAt(size()-1) will return the largest key.

        return mKeys[index];
public voidput(int key, boolean 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 = ContainerHelpers.binarySearch(mKeys, mSize, key);

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

            mKeys = GrowingArrayUtils.insert(mKeys, mSize, i, key);
            mValues = GrowingArrayUtils.insert(mValues, mSize, i, value);
            mSize++;
        }
public voidremoveAt(int index)

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        System.arraycopy(mKeys, index + 1, mKeys, index, mSize - (index + 1));
        System.arraycopy(mValues, index + 1, mValues, index, mSize - (index + 1));
        mSize--;
public voidsetValueAt(int index, boolean value)

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

        return mSize;
public java.lang.StringtoString()
{@inheritDoc}

This implementation composes a string by iterating over its mappings.

        if (size() <= 0) {
            return "{}";
        }

        StringBuilder buffer = new StringBuilder(mSize * 28);
        buffer.append('{");
        for (int i=0; i<mSize; i++) {
            if (i > 0) {
                buffer.append(", ");
            }
            int key = keyAt(i);
            buffer.append(key);
            buffer.append('=");
            boolean value = valueAt(i);
            buffer.append(value);
        }
        buffer.append('}");
        return buffer.toString();
public booleanvalueAt(int index)
Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this SparseBooleanArray stores.

The values corresponding to indices in ascending order are guaranteed to be associated with keys in ascending order, e.g., valueAt(0) will return the value associated with the smallest key and valueAt(size()-1) will return the value associated with the largest key.

        return mValues[index];