Android Array Move arrayMoveWithin(Object[] array, int moveFrom, int moveTo, int numToMove)

Description

Moves a number of entries in an array to another point in the array, shifting those inbetween as required.

License

Apache License

Parameter

Parameter	Description
array	The array to alter
moveFrom	The (0 based) index of the first entry to move
moveTo	The (0 based) index of the positition to move to
numToMove	The number of entries to move

Declaration

public static void arrayMoveWithin(Object[] array, int moveFrom,
        int moveTo, int numToMove) 

Method Source Code

//package com.java2s;
/* ====================================================================
 Licensed to the Apache Software Foundation (ASF) under one or more
 contributor license agreements.  See the NOTICE file distributed with
 this work for additional information regarding copyright ownership.
 The ASF licenses this file to You 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.//from ww  w. j a  v a 2  s  .com
 ==================================================================== */

public class Main {
    /**
     * Moves a number of entries in an array to another point in the array,
     *  shifting those inbetween as required.
     * @param array The array to alter
     * @param moveFrom The (0 based) index of the first entry to move
     * @param moveTo The (0 based) index of the positition to move to
     * @param numToMove The number of entries to move
     */
    public static void arrayMoveWithin(Object[] array, int moveFrom,
            int moveTo, int numToMove) {
        // If we're not asked to do anything, return now
        if (numToMove <= 0) {
            return;
        }
        if (moveFrom == moveTo) {
            return;
        }

        // Check that the values supplied are valid
        if (moveFrom < 0 || moveFrom >= array.length) {
            throw new IllegalArgumentException(
                    "The moveFrom must be a valid array index");
        }
        if (moveTo < 0 || moveTo >= array.length) {
            throw new IllegalArgumentException(
                    "The moveTo must be a valid array index");
        }
        if (moveFrom + numToMove > array.length) {
            throw new IllegalArgumentException(
                    "Asked to move more entries than the array has");
        }
        if (moveTo + numToMove > array.length) {
            throw new IllegalArgumentException(
                    "Asked to move to a position that doesn't have enough space");
        }

        // Grab the bit to move 
        Object[] toMove = new Object[numToMove];
        System.arraycopy(array, moveFrom, toMove, 0, numToMove);

        // Grab the bit to be shifted
        Object[] toShift;
        int shiftTo;
        if (moveFrom > moveTo) {
            // Moving to an earlier point in the array
            // Grab everything between the two points
            toShift = new Object[(moveFrom - moveTo)];
            System.arraycopy(array, moveTo, toShift, 0, toShift.length);
            shiftTo = moveTo + numToMove;
        } else {
            // Moving to a later point in the array
            // Grab everything from after the toMove block, to the new point
            toShift = new Object[(moveTo - moveFrom)];
            System.arraycopy(array, moveFrom + numToMove, toShift, 0,
                    toShift.length);
            shiftTo = moveFrom;
        }

        // Copy the moved block to its new location
        System.arraycopy(toMove, 0, array, moveTo, toMove.length);

        // And copy the shifted block to the shifted location
        System.arraycopy(toShift, 0, array, shiftTo, toShift.length);

        // We're done - array will now have everything moved as required
    }

    /**
     * This is really a debugging version of <code>System.arraycopy()</code>.
     * Use it to provide better exception messages when copying arrays around.
     * For production use it's better to use the original for speed.
     */
    public static void arraycopy(byte[] src, int src_position, byte[] dst,
            int dst_position, int length) {
        if (src_position < 0)
            throw new IllegalArgumentException(
                    "src_position was less than 0.  Actual value "
                            + src_position);
        if (src_position >= src.length)
            throw new IllegalArgumentException(
                    "src_position was greater than src array size.  Tried to write starting at position "
                            + src_position
                            + " but the array length is "
                            + src.length);
        if (src_position + length > src.length)
            throw new IllegalArgumentException(
                    "src_position + length would overrun the src array.  Expected end at "
                            + (src_position + length) + " actual end at "
                            + src.length);
        if (dst_position < 0)
            throw new IllegalArgumentException(
                    "dst_position was less than 0.  Actual value "
                            + dst_position);
        if (dst_position >= dst.length)
            throw new IllegalArgumentException(
                    "dst_position was greater than dst array size.  Tried to write starting at position "
                            + dst_position
                            + " but the array length is "
                            + dst.length);
        if (dst_position + length > dst.length)
            throw new IllegalArgumentException(
                    "dst_position + length would overrun the dst array.  Expected end at "
                            + (dst_position + length) + " actual end at "
                            + dst.length);

        System.arraycopy(src, src_position, dst, dst_position, length);
    }
}