sviolet.thistle.util.conversion.ArrayUtils Maven / Gradle / Ivy
/*
* Copyright (C) 2015-2021 S.Violet
*
* 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.
*
* Project GitHub: https://github.com/shepherdviolet/thistle
* Email: [email protected]
*/
package sviolet.thistle.util.conversion;
import java.util.Arrays;
/**
* Array Utils
*
* @author shepherdviolet
*/
public class ArrayUtils {
private static final int DEFRAGMENT_BUFFER_SIZE = 1024;
/**
* Delete useless elements in the array and place the remaining elements at the left end of the array
* @param array array
* @param predicate determine whether the element is retained, nullable
* @param Element type
* @return Number of remaining elements, return -1 if array is null
*/
public static int defragment(E[] array, DefragmentPredicate predicate) {
if (array == null) {
return -1;
}
if (array.length <= 0) {
return 0;
}
// array offset
int arrayOffset = 0;
// buff
Object[] buff = new Object[Math.min(array.length, DEFRAGMENT_BUFFER_SIZE)];
int buffOffset = 0;
// handle array
for (E element : array) {
// If the element is null, discard
if (element == null) {
continue;
}
// If predicate.isRetained returns false, discard
if (predicate != null && !predicate.isRetained(element)) {
continue;
}
// put element into buff
buff[buffOffset++] = element;
// flush to array
if (buffOffset >= buff.length) {
System.arraycopy(buff, 0, array, arrayOffset, buff.length);
arrayOffset += buff.length;
buffOffset = 0;
}
}
// flush to array
if (buffOffset > 0) {
System.arraycopy(buff, 0, array, arrayOffset, buffOffset);
arrayOffset += buffOffset;
buffOffset = 0;
}
// fill null
if (arrayOffset < array.length) {
Arrays.fill(array, arrayOffset, array.length, null);
}
// remaining length
return arrayOffset;
}
/**
* When defragmenting, determine whether the element is retained
* @param
*/
public interface DefragmentPredicate {
/**
* Determine whether the element is retained
* @param element element
* @return true: retain, false: discard
*/
boolean isRetained(E element);
}
}