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Merge "Support varargs for concatElements"

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This commit is contained in:
Al Sutton
2019-08-02 07:46:26 +00:00
committed by Android (Google) Code Review
parent 3f214d5867 3c072e6fe6
commit c71fb23b4b
2 changed files with 88 additions and 12 deletions
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64
core/java/com/android/internal/util/ArrayUtils.java
View File

@@ -320,23 +320,63 @@ public class ArrayUtils {
return array;
}
/**
* Combine multiple arrays into a single array.
*
* @param kind The class of the array elements
* @param arrays The arrays to combine
* @param <T> The class of the array elements (inferred from kind).
* @return A single array containing all the elements of the parameter arrays.
*/
@SuppressWarnings("unchecked")
public static @NonNull <T> T[] concatElements(Class<T> kind, @Nullable T[] a, @Nullable T[] b) {
final int an = (a != null) ? a.length : 0;
final int bn = (b != null) ? b.length : 0;
if (an == 0 && bn == 0) {
if (kind == String.class) {
return (T[]) EmptyArray.STRING;
} else if (kind == Object.class) {
return (T[]) EmptyArray.OBJECT;
public static @NonNull <T> T[] concatElements(Class<T> kind, @Nullable T[]... arrays) {
if (arrays == null || arrays.length == 0) {
return createEmptyArray(kind);
}
int totalLength = 0;
int maxLength = 0;
T[] maxLengthArray = arrays[0];
for (T[] item : arrays) {
if (item == null) {
continue;
}
totalLength += item.length;
if (item.length > maxLength) {
maxLengthArray = item;
maxLength = item.length;
}
}
final T[] res = (T[]) Array.newInstance(kind, an + bn);
if (an > 0) System.arraycopy(a, 0, res, 0, an);
if (bn > 0) System.arraycopy(b, 0, res, an, bn);
return res;
// Optimization for entirely empty arrays.
if (totalLength == 0) {
return createEmptyArray(kind);
}
final T[] all = (T[]) Array.newInstance(kind, totalLength);
int pos = 0;
for (T[] item : arrays) {
if (item == null || item.length == 0) {
continue;
}
System.arraycopy(item, 0, all, pos, item.length);
pos += item.length;
}
return all;
}
private static @NonNull <T> T[] createEmptyArray(Class<T> kind) {
if (kind == String.class) {
return (T[]) EmptyArray.STRING;
} else if (kind == Object.class) {
return (T[]) EmptyArray.OBJECT;
}
return (T[]) Array.newInstance(kind, 0);
}
/**
* Adds value to given array if not already present, providing set-like
* behavior.

36
core/tests/utiltests/src/com/android/internal/util/ArrayUtilsTest.java
View File

@@ -177,4 +177,40 @@ public class ArrayUtilsTest extends TestCase {
assertArrayEquals(new Long[] { 1L, 2L, 3L, 4L },
concatElements(Long.class, new Long[] { 1L, 2L }, new Long[] { 3L, 4L }));
}
public void testConcatElements_threeWay() {
String[] array1 = { "1", "2" };
String[] array2 = { "3", "4" };
String[] array3 = { "5", "6" };
String[] expectation = {"1", "2", "3", "4", "5", "6"};
String[] concatResult = ArrayUtils.concatElements(String.class, array1, array2, array3);
assertArrayEquals(expectation, concatResult);
}
public void testConcatElements_threeWayWithNull() {
String[] array1 = { "1", "2" };
String[] array2 = null;
String[] array3 = { "5", "6" };
String[] expectation = {"1", "2", "5", "6"};
String[] concatResult = ArrayUtils.concatElements(String.class, array1, array2, array3);
assertArrayEquals(expectation, concatResult);
}
public void testConcatElements_zeroElements() {
String[] expectation = new String[0];
String[] concatResult = ArrayUtils.concatElements(String.class);
assertArrayEquals(expectation, concatResult);
}
public void testConcatElements_oneNullElement() {
String[] expectation = new String[0];
String[] concatResult = ArrayUtils.concatElements(String.class, null);
assertArrayEquals(expectation, concatResult);
}
}