Java List Concatenate concatArrays(List arrays, int start, int size)

Description

Concatenate size many values from the passed in arrays, starting at offset start .

License

Apache License

Declaration

public static long[] concatArrays(List<long[]> arrays, int start, int size) 

Method Source Code

//package com.java2s;
/*//w  w w.  jav a  2s.com
 * Copyright 2014 the original author or authors.
 *
 * 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.
 */

import java.util.List;

public class Main {
    /**
     * Concatenate {@code size} many values from the passed in arrays, starting at offset {@code start}.
     */
    public static long[] concatArrays(List<long[]> arrays, int start, int size) {
        long[] result = new long[size];

        // How many values we still need to move over
        int howManyLeft = size;

        // Where in the resulting array we're currently bulk-writing
        int targetPosition = 0;

        // Where we're copying *from*, in (one of) the source array.
        // Typically 0, except maybe for the first array in the list
        int from = start;

        for (int i = 0; i < arrays.size() && howManyLeft > 0; i++) {
            long[] current = arrays.get(i);

            // Can't copy more than the current source array size, or the grand total pointer
            int howManyThisRound = Math.min(current.length - from, howManyLeft);
            System.arraycopy(current, from, result, targetPosition, howManyThisRound);
            from = 0;
            howManyLeft -= howManyThisRound;
            targetPosition += howManyThisRound;
        }

        // If this is non-zero here, means we were asked to copy more than what we were provided
        if (howManyLeft > 0) {
            throw new ArrayIndexOutOfBoundsException(
                    String.format("Not enough data, short of %d elements", howManyLeft));
        }
        return result;
    }
}

Related

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2. concat(List l1, List l2)
3. concat(List list, T... items)
4. concatAddresses(List addresses)
5. concatAll(final T[] empty, Iterable arrayList)
6. concatArraysToList(final T[]... arrays)
7. concatCsvLine(List values, String fieldSeparator)
8. concateAliases(List aliases)
9. concatElementsWithBrackets(List input)