Multiple column sorting.

Question

How does one sort multiple columns( date, String, time etc...). I want to sort by date where two dates can be alike as well. I could use HashMap for that reason.
Please help.
Thanks in advance.

Answer 1

Hi,
A demo of the comparator class is given below. I've tried to put it into the table class.
import java.util.*;
import javax.swing.*;
import java.awt.BorderLayout;
import java.awt.event.*;
import javax.swing.table.*;
import javax.swing.event.*;
class MultipleColumnSortTest
     MultipleColumnSortTest()
          JFrame frame = new JFrame("MultipleColumnSortTest");
          frame.setBounds(10,10,750,550);
          Vector fieldNames = new Vector();
          fieldNames.add("Dates");
          fieldNames.add("Strings");
          Vector dataVector = new Vector();
          for(int i = 0; i < 5; ++ i)
               Vector row = new Vector();
               row.add(new Date());
               row.add("abc" + i%2);
               dataVector.add(row);
          final SortableDataVector tableModel = new SortableDataVector(dataVector,fieldNames);
          int [] sortIndices = new int[2];
          sortIndices [0] = 0 ;
          sortIndices [1] = 1 ;
          tableModel.setSortPriority(sortIndices);
          JTable table = new JTable(tableModel);
          JScrollPane scrollpane = new JScrollPane(table);
          frame.getContentPane().add(scrollpane);
          JButton button = new JButton("Sort Data");
          frame.getContentPane().add(button,BorderLayout.SOUTH);
          button.addActionListener(new ActionListener()
               public void actionPerformed(ActionEvent event)
                    tableModel.setAscendingOrder(!tableModel.isAscendingOrder());
                    tableModel.sort();
          frame.setVisible(true);
     public static void main(String [] args)
          MultipleColumnSortTest appln = new MultipleColumnSortTest();
class SortableDataVector extends DefaultTableModel implements Comparator
     private int [] indices;
     private boolean isAscendingOrder;
     public SortableDataVector(Vector dataVector, Vector fieldNames)
          super(dataVector,fieldNames);
          setAscendingOrder(true);
     public void setAscendingOrder(boolean b)
          isAscendingOrder = b;
     public boolean isAscendingOrder()
          return isAscendingOrder;
     public void setSortPriority(int [] indices)
          this.indices = indices;
     public int compare(Object o1,Object o2)
          int comparisonResult = compareAscending(o1,o2);
          if(!isAscendingOrder)
               if(comparisonResult < 0)
                    comparisonResult = 1;
               else if (comparisonResult > 0)
                    comparisonResult = -1;               
          return comparisonResult;
     private int compareAscending(Object o1, Object o2)
          int comparisonResult = 0;
          if((o1 == null)&&(o2 != null))
               comparisonResult = -1;
          else if((o1 != null)&&(o2 == null))
               comparisonResult = 1;
          else if((o1 != null)&&(o2 != null))
               List firstRow = (List)o1;
               List secondRow = (List)o2;
               for(int i = 0; ((i < indices.length)&&(comparisonResult == 0)); ++i)
                    if(indices[i] < firstRow.size())
                         comparisonResult =
                              DatatypeSensitiveComparator.compare(
                                   firstRow.get(indices),
                                   secondRow.get(indices[i]));
          return comparisonResult;
     public boolean equals(Object obj)
          if(obj == null)
               return false;
          return this.equals(obj);
     public void sort()
          if((indices != null)&&(indices.length > 0))
               Collections.sort(dataVector,this);
               fireTableChanged(new TableModelEvent(this));
class DatatypeSensitiveComparator
     public static int compare(Object firstValue, Object secondValue)
          int comparisonResult = 0;
          if((firstValue != null)&&(secondValue == null))
               comparisonResult = 1;
          else if((firstValue == null)&&(secondValue != null))
               comparisonResult = -1;
          else if((firstValue != null)&&(secondValue != null))
               Class clazz = firstValue.getClass();
               if(!clazz.equals(secondValue.getClass()))
                    throw new IllegalArgumentException("Class are not the same ->"
                         + clazz.getName() + ":" +
                         secondValue.getClass().getName());
               if(clazz.equals(String.class))
                    comparisonResult = ((String)firstValue)
                         .compareTo(((String)secondValue));
               else if(clazz.equals(Date.class))
                    comparisonResult = ((Date)firstValue)
                         .compareTo(((Date)secondValue));
          return comparisonResult;