SparseIntArraypublic class SparseIntArray extends Object implements Cloneable| SparseIntArrays map integers to integers. Unlike a normal array of integers,
there can be gaps in the indices. It is intended to be more memory efficient
than using a HashMap to map Integers to Integers, 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 int[] | mValues | | private int | mSize |
| Constructors Summary |
|---|
public SparseIntArray()Creates a new SparseIntArray containing no mappings.
this(10);
| public SparseIntArray(int initialCapacity)Creates a new SparseIntArray 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.INT;
} else {
mKeys = ArrayUtils.newUnpaddedIntArray(initialCapacity);
mValues = new int[mKeys.length];
}
mSize = 0;
|
| Methods Summary |
|---|
| public void | append(int key, int 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 void | clear()Removes all key-value mappings from this SparseIntArray.
mSize = 0;
| | public android.util.SparseIntArray | clone()
SparseIntArray clone = null;
try {
clone = (SparseIntArray) super.clone();
clone.mKeys = mKeys.clone();
clone.mValues = mValues.clone();
} catch (CloneNotSupportedException cnse) {
/* ignore */
}
return clone;
| | public void | delete(int key)Removes the mapping from the specified key, if there was any.
int i = ContainerHelpers.binarySearch(mKeys, mSize, key);
if (i >= 0) {
removeAt(i);
}
| | public int | get(int key)Gets the int mapped from the specified key, or 0
if no such mapping has been made.
return get(key, 0);
| | public int | get(int key, int valueIfKeyNotFound)Gets the int 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 int | indexOfKey(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 int | indexOfValue(int 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 int | keyAt(int index)Given an index in the range 0...size()-1, returns
the key from the indexth key-value mapping that this
SparseIntArray 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 void | put(int key, int 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 void | removeAt(int index)Removes the mapping at the given index.
System.arraycopy(mKeys, index + 1, mKeys, index, mSize - (index + 1));
System.arraycopy(mValues, index + 1, mValues, index, mSize - (index + 1));
mSize--;
| | public int | size()Returns the number of key-value mappings that this SparseIntArray
currently stores.
return mSize;
| | public java.lang.String | toString(){@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('=");
int value = valueAt(i);
buffer.append(value);
}
buffer.append('}");
return buffer.toString();
| | public int | valueAt(int index)Given an index in the range 0...size()-1, returns
the value from the indexth key-value mapping that this
SparseIntArray 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];
|
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