The height of a row in a JTable component is based on an assigned value rather than on the preferred height of the renderers used in that row. You can either set a default height for all rows or set the heights for individual rows. 
This example demonstrates a few routines that can be used to adjust the height of rows in applications where the row heights can vary. 

    int rows = 10;
    int cols = 5;
    JTable table = new JTable(rows, cols);
    
    // Set the 1st row to 60 pixels high
    table.setRowHeight(0, 60);
    
    // Set the height of all rows to 32 pixels high,
    // regardless if any heights were assigned to particular rows
    table.setRowHeight(32);
    // the height of the 1st row is set to 32 pixels high
    
    // Returns the preferred height of a row.
    // The result is equal to the tallest cell in the row.
    public int getPreferredRowHeight(JTable table, int rowIndex, int margin) {
        // Get the current default height for all rows
        int height = table.getRowHeight();
    
        // Determine highest cell in the row
        for (int c=0; c<table.getColumnCount(); c++) {
            TableCellRenderer renderer = table.getCellRenderer(rowIndex, c);
            Component comp = table.prepareRenderer(renderer, rowIndex, c);
            int h = comp.getPreferredSize().height + 2*margin;
            height = Math.max(height, h);
        }
        return height;
    }
    
    // The height of each row is set to the preferred height of the
    // tallest cell in that row.
    public void packRows(JTable table, int margin) {
        packRows(table, 0, table.getRowCount(), margin);
    }
    
    // For each row >= start and < end, the height of a
    // row is set to the preferred height of the tallest cell
    // in that row.
    public void packRows(JTable table, int start, int end, int margin) {
        for (int r=0; r<table.getRowCount(); r++) {
            // Get the preferred height
            int h = getPreferredRowHeight(table, r, margin);
    
            // Now set the row height using the preferred height
            if (table.getRowHeight(r) != h) {
                table.setRowHeight(r, h);
            }
        }
    }