Come ordinare un ArrayList utilizzando più criteri di ordinamento?

Question

Ho un elenco di array che contiene oggetti Quote. Voglio essere in grado di ordinare alfabeticamente per nome, per modifica e per variazione percentuale. Come posso ordinare il mio 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

Creare un appropriato Comparator che confronterà due elementi in base ai criteri desiderati. Quindi usa Collections.sort() sul tuo ArrayList.

Se in un secondo momento si desidera ordinare in base a criteri diversi, chiamare di nuovo Collections.sort() con un altro Comparator.

Answer 2

Sun ha dedicato gran parte della sua tutorial per l'ordinamento in collezioni di Java:
http://download.oracle.com/javase/tutorial/collections/interfaces/order.html

Si discute entrambe le interfacce comparabili e comparatore con esempi.

Answer 3

Vedi Collections.sort con un comparatore esplicita (o la Collections.sort tipo che richiede l'input di implementare Comparable, se si preferisce).

Answer 4

Se (quasi) si desidera utilizzare sempre tale ordine, è possibile aggiungere l'interfaccia Comparable a Quote e implementare un metodo di confronto.

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; 
} 

Quindi utilizzare una raccolta ordinata o ordinare un elenco e le virgolette verranno ordinate.

Per l'ordinamento ad hoc, un comparatore separato, possibilmente anonimo, è migliore.

Answer 5

Tutti hanno ragione a voler utilizzare i Comparatori. Estendendosi su questa idea, se si vuole essere in grado di ordinare su più criteri, quindi una classe come questo lavoro per voi:

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; 
    } 
} 

Poi basta scrivere comparatori molto semplici per qualsiasi campi si desidera e si possono combinare loro in comparatori più complessi più facilmente e con più riutilizzo.

Answer 6

Dai un'occhiata alla ComparatorChain della Apache Commons Collection. Questo dovrebbe fare il lavoro. Non implementare la logica se è già disponibile e testata.
Nel seguente sito ho un tutorial: Sorting Objects By Multiple Attributes"