Ranges

import java.util.*;


public class What {

    // prerequisitions

    static class Range {
        public final int begin;
        public final int end;

        public Range(int begin, int end) {
            this.begin = begin;
            this.end = end;
        }
    }

    public static void main(String[] args) {
        Map<String, Range> map = new LinkedHashMap<>();
        map.put("Action1", new Range( 0, 10));
        map.put(   "Act2", new Range(10, 30));
        map.put("Action3", new Range(20, 50));
        map.put("Trivial", new Range( 0,  5));

        System.out.println(new What().generateBarChart(map, 10));
    }

    // actual code starts here

    private String findLongestKey(Collection<String> strings) {
        int max = -1;
        String maxs = null;
        for(String s : strings) {
            if(s.length() > max) {
                maxs = s;
                max = s.length();
            }
        }
        return maxs;
    }

    private Range findInterval(Iterable<Range> ranges) {
        int min = Integer.MAX_VALUE;
        int max = Integer.MIN_VALUE;

        for(Range r: ranges) {
            if(min>r.begin)
                min = r.begin;
            if(max<r.end)
                max = r.end;
        }

        return new Range(min, max);
    }

    private String makeBar(Range range, int stepSize, Range interval) {
        String bar = "";

        int begin = interval.begin / stepSize;
        int end = interval.end / stepSize;

        for(int i= begin; i< end; i++) {
            int min = i*stepSize;
            int max = min+stepSize;

            if(min>=range.begin && max<=range.end)
                bar += "*";
            else
                bar += "-";
        }
        return bar;
    }

    public String generateBarChart(Map<String, Range> data, int stepSize) {
        String out = "";

        int longest = findLongestKey(data.keySet()).length();
        Range interval = findInterval(data.values());

        for(Map.Entry<String, Range> entry : data.entrySet()) {
            String bar = makeBar(entry.getValue(), stepSize, interval);

            if(!bar.contains("*"))
                continue;

            out += String.format("%" + longest + "s", entry.getKey()) + ": " + bar + "\n";
        }

        return out;
    }

}