The following code works normally on b55, but on b56 exception is throwing.

====== Code ======
import javax.swing.RowSorter;
import javax.swing.SortOrder;
import javax.swing.table.TableModel;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.TableRowSorter;
import java.util.Comparator;
import java.util.LinkedList;

public class TestBug {
    private Integer[][] modelData = {
            {0, 1, 2},
            {2, 0, 1}
    };
    private Integer[] columnNames = {1, 2, 3};

    class TestComparator implements Comparator<Integer> {
        public int compare(Integer i1, Integer i2) {
            if (i1 == 0) i1 = 100;
            if (i2 == 0) i2 = 100;
            return i1 - i2;
        }
    }

    private void test() {
        TableModel model = new DefaultTableModel(modelData, columnNames);
        LinkedList<RowSorter.SortKey> keys =
                new LinkedList<RowSorter.SortKey>();
        TableRowSorter<TableModel> rs = new TableRowSorter<TableModel>(model);
        // at the first time everything is ok
        rs.setComparator(1, new TestComparator());
        keys.add(new RowSorter.SortKey(1, SortOrder.ASCENDING));
        System.out.println("Check point");
        rs.setSortKeys(keys);
        // at the second time:
        // java.lang.ClassCastException: java.lang.String
        // cannot be cast to java.lang.Integer
        keys.clear();
        rs.setComparator(2, new TestComparator());
        keys.add(new RowSorter.SortKey(2, SortOrder.ASCENDING));
        rs.setSortKeys(keys);
    }

    public static void main(String[] args) {
        TestBug t = new TestBug();
        t.test();
    }
}
======= Output ========
Check point
Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
at TableRowSorter.TestBug$TestComparator.compare(TestBug.java:19)
at javax.swing.DefaultRowSorter.compare(DefaultRowSorter.java:869)
at javax.swing.DefaultRowSorter.access$100(DefaultRowSorter.java:91)
at javax.swing.DefaultRowSorter$Row.compareTo(DefaultRowSorter.java:1277)
at javax.swing.DefaultRowSorter$Row.compareTo(DefaultRowSorter.java:1267)
at java.util.Arrays.mergeSort(Arrays.java:1147)
at java.util.Arrays.sort(Arrays.java:1082)
at javax.swing.DefaultRowSorter.sortExistingData(DefaultRowSorter.java:477)
at javax.swing.DefaultRowSorter.setSortKeys(DefaultRowSorter.java:251)
at TableRowSorter.TestBug.test(TestBug.java:40)
at TableRowSorter.TestBug.main(TestBug.java:48)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:589)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:86)

Process finished with exit code 1