setValueAt(Object aValue, int row, int col)

问题

I am trying to change a value in the Object[][] data in a defaultTableModel but I am getting a nullpointerexception at if (data[i][j] == userFolderName)I have tried changing the variable to "Kathy" just in case it wasn't reading the userName correctly but it still throws the exception. Can you please have a look at my code and see where I'm going wrong?

public class Statistics extends JPanel {
    public Object[][] data;
    public DefaultTableModel model;

public Statistics() {
    super(new GridLayout(1,0));
    String[] columnNames = {"Name", "Games Played", "Games Won"};
    Object[][] data = {
            {"Kathy", new Integer(5), new Integer(2)},
            {"Steve", new Integer(2), new Integer(0)},
    };
    model = new DefaultTableModel(data, columnNames);
    JTable table = new JTable(model);
    table.setFillsViewportHeight(true);
    table.setVisible(true);
    table.setEnabled(false);

    JScrollPane scrollPane = new JScrollPane(table);
    add(scrollPane);
}

public void addRow(Object[] objects) {
    model.addRow(objects);

}

public void updateGamesPlayed(String userFolderName, int gamesPlayed) {
    int rowCount = model.getRowCount();
    int columnCount = model.getColumnCount();
    for (int i = 0; i < rowCount; i++){
        for(int j = 0; j < columnCount; j++){
            if (data[i][j] == userFolderName){
                model.setValueAt(gamesPlayed, i, j+1);
            }
        }
    }

}


}

回答1:

You have two different data objects - a global one and a local one in your constructor. If you change Object[][] data = {...}; to data = new Object[][]{...}; in your constructor it should work as you're only setting the local one, not the global value.

回答2:

btw

model.setValueAt(gamesPlayed, i, j+1);

this j+1 will cause OutOfBoundsException

来源：https://stackoverflow.com/questions/19537533/setvalueatobject-avalue-int-row-int-col