Grouping Samples

Grouping.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class GroupingBefore8 {

    public static void main(String[] args) {

        List<Integer> in = new ArrayList<>();
        in.add(1);
        in.add(2);
        in.add(3);
        in.add(1);
        in.add(1);
        in.add(3);
        in.add(3);
        in.add(3);

        log("** input");
        logList(in);

        log("** grouping 1");
        GroupingBefore8 t = new GroupingBefore8();
        List<Integer> ret = t.grouping1(in, Collections.<Integer>reverseOrder());
        logList(ret);

        log("** grouping 2");
        List<List<Integer>> ret2 = t.grouping2(in, Collections.<Integer>reverseOrder());
        logListList(ret2);

        log("** grouping 3");
        List<List<Integer>> ret3 = t.grouping3(in, Collections.<Integer>reverseOrder());
        logListList(ret3);

        log("** grouping 4");
        Map<Integer, List<Integer>> ret4 = t.grouping4(in, Collections.<Integer>reverseOrder());
        log(ret4);

    }


    public <T> List<T> grouping1(List<T> list, Comparator<T> comp) {

        List<T> ret = new ArrayList<T>();

        List<T> tmp = new ArrayList<T>(list);
        while(tmp.size()>0) {
            T myT = tmp.get(0);
            tmp.remove(myT);

            ret.add(myT);
            Iterator<T> iter = tmp.iterator();
            while(iter.hasNext()) {
                T yourT = iter.next();
                if (comp.compare(myT, yourT) == 0) {
                    iter.remove();
                }
            }
        }
        return ret;
    }

    public <T> List<List<T>> grouping2(List<T> list, Comparator<T> comp) {

        List<List<T>> ret = new ArrayList<List<T>>();

        List<T> tmp = new ArrayList<T>(list);
        while(tmp.size()>0) {
            T myT = tmp.get(0);
            tmp.remove(myT);

            List<T> tmpInner = new ArrayList<T>();
            tmpInner.add(myT);

            Iterator<T> iter = tmp.iterator();
            while(iter.hasNext()) {
                T yourT = iter.next();
                if (comp.compare(myT, yourT) == 0) {
                    tmpInner.add(yourT);
                    iter.remove();
                }else {
                    break;
                }
            }
            ret.add(tmpInner);
        }
        return ret;
    }

    public <T> List<List<T>> grouping3(List<T> list, Comparator<T> comp) {

        List<List<T>> ret = new ArrayList<List<T>>();

        List<T> tmp = new ArrayList<T>(list);
        while(tmp.size()>0) {
            T myT = tmp.get(0);
            tmp.remove(myT);

            List<T> tmpInner = new ArrayList<T>();
            tmpInner.add(myT);

            Iterator<T> iter = tmp.iterator();
            while(iter.hasNext()) {
                T yourT = iter.next();
                if (comp.compare(myT, yourT) == 0) {
                    tmpInner.add(yourT);
                    iter.remove();
                }
            }
            ret.add(tmpInner);
        }
        return ret;
    }

    public <T> Map<T,List<T>> grouping4(List<T> list, Comparator<T> comp) {

        Map<T,List<T>> ret = new HashMap<T, List<T>>();

        List<T> tmp = new ArrayList<T>(list);
        while(tmp.size()>0) {
            T myT = tmp.get(0);
            tmp.remove(myT);

            List<T> tmpInner = new ArrayList<T>();
            tmpInner.add(myT);

            ret.put(myT, tmpInner);

            Iterator<T> iter = tmp.iterator();
            while(iter.hasNext()) {
                T yourT = iter.next();
                if (comp.compare(myT, yourT) == 0) {
                    tmpInner.add(yourT);
                    iter.remove();
                }
            }
        }
        return ret;
    }

    private static <T> void logListList(List<List<T>> list) {
        for (List<T> item: list) {
            System.out.println(item);
        }
    }

    private static <T> void logList(List<T> list) {
        System.out.println(list);
    }

    private static void log(Object obj) {
        System.out.println(obj);
    }


}

//* input
//[1, 2, 3, 1, 1, 3, 3, 3]
//* grouping 1
//[1, 2, 3]
//* grouping 2
//[1]
//[2]
//[3]
//[1, 1]
//[3, 3, 3]
//* grouping 3
//[1, 1, 1]
//[2]
//[3, 3, 3, 3]
//* grouping 4
//{1=[1, 1, 1], 2=[2], 3=[3, 3, 3, 3]}