An example of how to sort data elements by groupings, and determining where the starting line number. This assumes that the data is presented in the grouping shown {1, 0, 2, 6, 3, 5, 4}, and assumes you want to sort it in the order {0, 1, 2, 3, 4, 5, 6}

GroupedRowSorting.java

/*
 * Copyright 2015 John Yeary <jyeary@bluelotussoftware.com>.
 *
 * 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.
 */
package com.bluelotussoftware.example;

import java.text.MessageFormat;
import java.util.Arrays;
import java.util.Map;
import java.util.TreeMap;

/**
 *
 * @author John Yeary <jyeary@bluelotussoftware.com>
 * @version 1.0
 */
public class GroupedRowSorting {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        int[] rowSortOrder = new int[]{1, 0, 2, 6, 3, 5, 4};
        System.out.println(MessageFormat.format("Number of Groups: {0} and the sorting order {1}", rowSortOrder.length, Arrays.toString(rowSortOrder)));
        Map<Integer, Integer> lengths = new TreeMap<>();

        // Add some predictable bogus length values for each group of data.
        for (int i = 0; i < rowSortOrder.length; i++) {
            lengths.put(rowSortOrder[i], i + 1);// Here is where we would use a real length value.
        }

        // Print out our data so we can manually tabulate it to check results
        System.out.println(MessageFormat.format("The array of length values per row {0}", lengths.entrySet()));

        for (int i = 0; i < rowSortOrder.length; i++) {
            int startingLineNumber = 0;
            for (int j = 0; j < rowSortOrder[i]; j++) {
                startingLineNumber += lengths.get(j);
            }
            System.out.println(MessageFormat.format("RowSortOrder {0} starts at line {1}", rowSortOrder[i], startingLineNumber));
        }
    }
}