How to sort an ArrayList using multiple sorting criteria?

Question

I have an array list that contains Quote objects. I want to be able to sort alphabetically by name, by change, and by percent change. How can I sort my arraylist?

package org.stocktwits.model;

import java.io.Serializable;
import java.text.DecimalFormat;

    public class Quote implements Serializable {

        private static final long serialVersionUID = 1L;

        public String symbol;
        public String name;
        public String change;
        public String percentChange;
        public String open;
        public String daysHigh;
        public String daysLow;
        public String dividendYield;
        public String volume;
        public String averageDailyVolume;
        public String peRatio;
        public String marketCapitalization;
        public String yearHigh;
        public String yearLow;
        public String lastTradePriceOnly;
        public DecimalFormat df = new DecimalFormat("#,###,###,###,###,##0.00");
        public DecimalFormat vf = new DecimalFormat("#,###,###,###,###,##0");

        public String getSymbol() {
            return symbol;
        }
        public void setSymbol(String symbol) {
            this.symbol = symbol;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getChange() {
            return change;
        }
        public void setChange(String change) {
            if(change.equals("null")){
                this.change = "N/A";
            }
            else{   
                float floatedChange = Float.valueOf(change);
                this.change = (df.format(floatedChange));
            }
        }
        public String getPercentChange() {
            return percentChange;
        }
        public void setPercentChange(String percentChange) {
            if(percentChange.equals("null"))
                percentChange = "N/A";
            else
                this.percentChange = percentChange;
        }
        public String getOpen() {
            return open;
        }
        public void setOpen(String open) {
            if(open.equals("null"))
                this.open = "N/A";
            else
                this.open = open;
        }
        public String getDaysHigh() {
            return daysHigh;
        }
        public void setDaysHigh(String daysHigh) {
            if(daysHigh.equals("null"))
                this.daysHigh = "N/A";
            else{
                float floatedDaysHigh = Float.valueOf(daysHigh);
                this.daysHigh = (df.format(floatedDaysHigh));
            }
        }
        public String getDaysLow() {
            return daysLow;
        }
        public void setDaysLow(String daysLow) {
            if(daysLow.equals("null"))
                this.daysLow = "N/A";
            else{
                float floatedDaysLow = Float.valueOf(daysLow);
                this.daysLow = (df.format(floatedDaysLow));
            }
        }
        public String getVolume() {
            return volume;
        }
        public void setVolume(String volume) {
            if(volume.equals("null")){
                this.volume = "N/A";
            }
            else{
                float floatedVolume = Float.valueOf(volume);
                this.volume = (vf.format(floatedVolume));
            }
        }
        public String getDividendYield() {
            return dividendYield;
        }
        public void setDividendYield(String dividendYield) {
            if(dividendYield.equals("null"))
                this.dividendYield = "N/A";
            else
                this.dividendYield = dividendYield;
        }
        public String getAverageDailyVolume() {
            return averageDailyVolume;
        }
        public void setAverageDailyVolume(String averageDailyVolume) {
            if(averageDailyVolume.equals("null")){
                this.averageDailyVolume = "N/A";
            }
            else{
                float floatedAverageDailyVolume = Float.valueOf(averageDailyVolume);
                this.averageDailyVolume = (vf.format(floatedAverageDailyVolume));
            }
        }
        public String getPeRatio() {
            return peRatio;
        }
        public void setPeRatio(String peRatio) {
            if(peRatio.equals("null"))
                this.peRatio = "N/A";
                else
            this.peRatio = peRatio;
        }
        public String getMarketCapitalization() {
            return marketCapitalization;
        }
        public void setMarketCapitalization(String marketCapitalization) {
            if(marketCapitalization.equals("null"))
                this.marketCapitalization = "N/A";
            else
                this.marketCapitalization = marketCapitalization;
        }
        public String getYearHigh() {
            return yearHigh;
        }
        public void setYearHigh(String yearHigh) {
            if(yearHigh.equals("null"))
                this.yearHigh = "N/A";
            else
                this.yearHigh = yearHigh;
        }
        public String getYearLow() {
            return yearLow;
        }
        public void setYearLow(String yearLow) {
            if(yearLow.equals("null"))
                this.yearLow = "N/A";
            else
                this.yearLow = yearLow;
        }

        public String getLastTradePriceOnly() {
            return lastTradePriceOnly;
        }

        public void setLastTradePriceOnly(String lastTradePriceOnly) {
            if(lastTradePriceOnly.equals("null")){
                this.lastTradePriceOnly = "N/A";
            }
            else{
                float floatedLastTradePriceOnly = Float.valueOf(lastTradePriceOnly);
                this.lastTradePriceOnly = (df.format(floatedLastTradePriceOnly));
            }
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + ((change == null) ? 0 : change.hashCode());
            result = prime * result
                    + ((daysHigh == null) ? 0 : daysHigh.hashCode());
            result = prime * result + ((daysLow == null) ? 0 : daysLow.hashCode());
            result = prime
                    * result
                    + ((lastTradePriceOnly == null) ? 0 : lastTradePriceOnly
                            .hashCode());
            result = prime
                    * result
                    + ((marketCapitalization == null) ? 0 : marketCapitalization
                            .hashCode());
            result = prime * result + ((name == null) ? 0 : name.hashCode());
            result = prime * result + ((open == null) ? 0 : open.hashCode());
            result = prime * result + ((peRatio == null) ? 0 : peRatio.hashCode());
            result = prime * result
                    + ((percentChange == null) ? 0 : percentChange.hashCode());
            result = prime * result + ((symbol == null) ? 0 : symbol.hashCode());
            result = prime * result + ((volume == null) ? 0 : volume.hashCode());
            result = prime * result
                    + ((yearHigh == null) ? 0 : yearHigh.hashCode());
            result = prime * result + ((yearLow == null) ? 0 : yearLow.hashCode());
            return result;
        }
        @Override
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            Quote other = (Quote) obj;
            if (change == null) {
                if (other.change != null)
                    return false;
            } else if (!change.equals(other.change))
                return false;
            if (daysHigh == null) {
                if (other.daysHigh != null)
                    return false;
            } else if (!daysHigh.equals(other.daysHigh))
                return false;
            if (daysLow == null) {
                if (other.daysLow != null)
                    return false;
            } else if (!daysLow.equals(other.daysLow))
                return false;
            if (lastTradePriceOnly == null) {
                if (other.lastTradePriceOnly != null)
                    return false;
            } else if (!lastTradePriceOnly.equals(other.lastTradePriceOnly))
                return false;
            if (marketCapitalization == null) {
                if (other.marketCapitalization != null)
                    return false;
            } else if (!marketCapitalization.equals(other.marketCapitalization))
                return false;
            if (name == null) {
                if (other.name != null)
                    return false;
            } else if (!name.equals(other.name))
                return false;
            if (open == null) {
                if (other.open != null)
                    return false;
            } else if (!open.equals(other.open))
                return false;
            if (peRatio == null) {
                if (other.peRatio != null)
                    return false;
            } else if (!peRatio.equals(other.peRatio))
                return false;
            if (percentChange == null) {
                if (other.percentChange != null)
                    return false;
            } else if (!percentChange.equals(other.percentChange))
                return false;
            if (symbol == null) {
                if (other.symbol != null)
                    return false;
            } else if (!symbol.equals(other.symbol))
                return false;
            if (volume == null) {
                if (other.volume != null)
                    return false;
            } else if (!volume.equals(other.volume))
                return false;
            if (yearHigh == null) {
                if (other.yearHigh != null)
                    return false;
            } else if (!yearHigh.equals(other.yearHigh))
                return false;
            if (yearLow == null) {
                if (other.yearLow != null)
                    return false;
            } else if (!yearLow.equals(other.yearLow))
                return false;
            return true;
        }
    }

Answer 1

If you (almost) always want to use that order you can add the Comparable interface to Quote and implement a compareTo method.

 public int compareTo(Quote quote) {
     int result = this.getName().compareTo(quote.getName());
     if (result == 0) {
        result = this.getChange().compareTo(quote.getChange());
     }
     if (result == 0) {
        result = this.getPercentChange().compareTo(quote.getPercentChange());
     }
     return result;
 }

Then use a sorted collection, or sort a list, and the quotes will be sorted.

For ad hoc sorting, a separate, possibly anonymous, Comparator is better.

Answer 2

Everybody is right that you want to use Comparators. Extending on that idea, if you want to be able to sort on multiple criteria, then a class like this will work for you:

public class MultiComparator<T> implements Comparator<T> {
    private List<Comparator<T>> comparators;

    public MultiComparator(List<Comparator<T>> comparators) {
        this.comparators = comparators;
    }

    public int compare(T o1, T o2) {
        for (Comparator<T> comparator : comparators) {
            int comparison = comparator.compare(o1, o2);
            if (comparison != 0) return comparison;
        }
        return 0;
    }
}

Then you just write really simple comparators for whichever fields you desire and you can combine them into more complex comparators more easily and with more reuse.