Using an insertion sort algorithm using more than one field from an array of objects

Question

I have to sort an array with state objects and sort it by region number, and population. I have imported this information from a text file so these are strings. I can sort using one of the fields but cant get it to work with both. It always just ends up sorting the last sort called in the method. For instance in my code it just finishes with sorting the region number, which unsorts the population. Is there anyway to sort by population, and then from that sort, sort the region number. Also, i cant use anything from java.util.

public void insertionSort()
    {
        int in, out;

        for (out = 1; out < getElementCount(); out++)
        {
            State temp = states[out];
            in = out;

            while (in > 0 && states[in - 1].getPopulation().compareTo(temp.getPopulation()) > 0)
            {
                states[in] = states[in - 1];
                --in;
            }
            states[in] = temp;

        }
         for (out = 1; out < getElementCount(); out++)
        {
            State temp = states[out];
            in = out;

            while (in > 0 && states[in - 1].getRegionNumber().compareTo(temp.getRegionNumber()) > 0)
            {
                states[in] = states[in - 1];
                --in;
            }
            states[in] = temp;
    }
    }




 public void Execute()
    {
        StateCollection sc = new StateCollection();

        String filename = "States.Search.txt";
        String file = "States.Input.txt";

        String[] stateSearch = new String[15];
        String[] state = new String[50];


        stateSearch = readFile(filename, stateSearch);
        state = readFile(file, state);

        for (int i = 0; i < state.length; i++)
        {

            String stateName = state[i].substring(0, 15).trim();
            String stateCapital = state[i].substring(15, 30).trim();
            String abbr = state[i].substring(30, 32).trim();
            String population = state[i].substring(32, 40).trim();
            String region = state[i].substring(40, 55).trim();
            String regionNumber = state[i].substring(55).trim();

            State s = new State(stateName, stateCapital, abbr, population, region, regionNumber);

            sc.add(i, s);


        }


        sc.bubbleSort();

Answer 1

Separate your problem into smaller problems which are easier to solve.

Sorting logic :

public void insertionSort() {
    int in, out;

    for (out = 1; out < getElementCount(); out++) {
        State temp = states[out];
        in = out;

        while (in > 0 && compare(states[in-1], temp) > 0) {
            states[in] = states[in - 1];
            --in;
        }
        states[in] = temp;

    }
}

Comparision logic :

int compare( State a, State b )
{
    int comparePopulation =  a.getPopulation().compareTo(b.getPopulation());
    if ( comparePopulation!=0 )
        return comparePopulation;
    else
        return a.getRegionNumber().compareTo(b.getRegionNumber());
}

That sorts 1st by population and then by region number.

Here follows a Minimal, Complete, and Verifiable example

import java.util.concurrent.ThreadLocalRandom;

class Test {

static int compare(State a, State b) {
    int comparePopulation = a.getPopulation().compareTo(b.getPopulation());
    if (comparePopulation != 0) {
        return comparePopulation;
    } else {
        return a.getRegionNumber().compareTo(b.getRegionNumber());
    }
}

static void insertionSort() {
    int in, out;

    for (out = 1; out < getElementCount(); out++) {
        State temp = states[out];
        in = out;

        while (in > 0 && compare(states[in - 1], temp) > 0) {
            states[in] = states[in - 1];
            --in;
        }
        states[in] = temp;

    }
}

static class State {

    private final Integer population;
    private final Integer regionNumber;

    public State(int population, int regionNumber) {
        this.population = population;
        this.regionNumber = regionNumber;
    }

    public static State getRandomState() {
        return new State(ThreadLocalRandom.current().nextInt(10, 14),
                ThreadLocalRandom.current().nextInt(1, 4));
    }

    public Integer getRegionNumber() {
        return regionNumber;
    }

    public Integer getPopulation() {
        return population;
    }

    @Override
    public String toString() {
        return "P=" + population + " R=" + regionNumber;
    }
}

static int getElementCount() {
    return states.length;
}

static State[] states;

public static void main(String[] args) {
    // Create 10 random states
    states = new State[10];
    for (int n = 0; n < 10; ++n) {
        states[n] = State.getRandomState();
    }
    // Print them
    System.out.println("----States unsorted----");
    for (State s : states) {
        System.out.println(s);
    }
    // Sort
    insertionSort();
    // Print them sorted
    System.out.println("----States sorted----");
    for (State s : states) {
        System.out.println(s);
    }
}

}

It generates 10 random states, prints them, sorts them and prints them sorted. In the output we can see that the states are properly sorted 1st by population and among those with the same population they are "sub-sorted" by region number.

----States unsorted----
P=10 R=1
P=10 R=2
P=12 R=1
P=11 R=2
P=11 R=2
P=13 R=1
P=12 R=2
P=13 R=1
P=10 R=2
P=12 R=1
----States sorted----
P=10 R=1
P=10 R=2
P=10 R=2
P=11 R=2
P=11 R=2
P=12 R=1
P=12 R=1
P=12 R=2
P=13 R=1
P=13 R=1

Answer 2

You can declare State class that implements Comparator as follow:

  public class State implements Comparator<State> {
     // your fields
     // getter and setter;
    @Override
    public int compare(State o1, State o2) {
      int sort1 = o1.getPopulation().compareTo(o2.getPopulation());
      if (sort1 != 0) {
         return sort1;
      }
      int sort2 = o1.getRegionNumber().compareTo(o2.getRegionNumber());
      if (sort2 != 0) {
         return sort2;
      }
      else{
       // other fields as you like. 
      }
   }

 }