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<TITLE>Sorting a Column in a JTable Component
(Java Developers Almanac Example)
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<B><A HREF="../javax.swing.table/pkg.html#Sorting">Sorting</A></B><font color="#666666" SIZE="-2">
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<h3>
e961.
Sorting a Column in a JTable Component</h3>
This example implements a method that sorts the data of a particular
column of a <code>DefaultTableModel</code>.
<pre>
DefaultTableModel model = new DefaultTableModel();
JTable table = new JTable(model);
// Add data here
// Disable autoCreateColumnsFromModel otherwise all the
// column customizations and adjustments will be lost
// when the model data is sorted
table.setAutoCreateColumnsFromModel(false);
// Sort the values in the second column of the model
// in descending order
int mColIndex = <font color="#0066ff"><i>1</i></font>;
boolean ascending = <font color="#0066ff"><i>false</i></font>;
sortColumn(model, mColIndex, ascending);
// Regardless of sort order (ascending or descending),
// null values always appear last.
// colIndex specifies a column in model.
public void sortColumn(DefaultTableModel model, int colIndex, boolean ascending) {
Vector data = model.getDataVector();
Object[] colData = new Object[model.getRowCount()];
// Copy the column data in an array
for (int i=0; i<colData.length; i++) {
colData[i] = ((Vector)data.get(i)).get(colIndex);
}
// Sort the array of column data
Arrays.sort(colData, new ColumnSorter(ascending));
// Copy the sorted values back into the table model
for (int i=0; i<colData.length; i++) {
((Vector)data.get(i)).set(colIndex, colData[i]);
}
model.fireTableStructureChanged();
}
public class ColumnSorter implements Comparator {
boolean ascending;
ColumnSorter(boolean ascending) {
this.ascending = ascending;
}
public int compare(Object a, Object b) {
// Treat empty strains like nulls
if (a instanceof String && ((String)a).length() == 0) {
a = null;
}
if (b instanceof String && ((String)b).length() == 0) {
b = null;
}
// Sort nulls so they appear last, regardless
// of sort order
if (a == null && b == null) {
return 0;
} else if (a == null) {
return 1;
} else if (b == null) {
return -1;
} else if (a instanceof Comparable) {
if (ascending) {
return ((Comparable)a).compareTo(b);
} else {
return ((Comparable)b).compareTo(a);
}
} else {
if (ascending) {
return a.toString().compareTo(b.toString());
} else {
return b.toString().compareTo(a.toString());
}
}
}
}
</pre>
<P><table width="600" CELLSPACING="0" CELLPADDING="2" BORDER="0">
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Related Examples
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e960. <a class="eglink" href="Sorter.html?l=rel">
Sorting the Rows in a JTable Component Based on a Column
</a>
<br>
<table width="600" CELLSPACING="0" CELLPADDING="2" BORDER="0">
<tr>
<td align="left">
<br>
See also:
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Cells">
Cells
</a>
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Column%20Heads">
Column Heads
</a>
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Columns">
Columns
</a>
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Editing">
Editing
</a>
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Events">
Events
</a>
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Layout">
Layout
</a>
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Rows">
Rows
</a>
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Scrolling">
Scrolling
</a>
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Selection">
Selection
</a>
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Table%20Model">
Table Model
</a>
<a class="eglink" href="/egs/javax.swing.table/pkg.html?l=rel#Tool%20Tips">
Tool Tips
</a>
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