How to change or find column type in JTable

Question

I want to insert JCheckBox in every row in JTable so I try to change my first column type. When I try this code, I get "java.lang.String cannot be cast to java.lang.Boolean" error.

 DefaultTableModel model=new DefaultTableModel(){
            private static final long serialVersionUID = 1L;  
             @Override
            public Class<?> getColumnClass(int column) {  
                    switch (column) {  
                        case 0:
                            return Boolean.class;
                        case 1:  
                            return String.class;
                        case 2:  
                            return String.class;
                        case 3:  
                            return String.class; 
                        default:
                            return   String.class;
                    }  
           } 
   }

Answer 1

static String[] columnNames={"Name","Surname","Boolean"};
static Object[][] data={ {null,null,null };
JTable table=new JTable(data,columnNames);


public static void RESULTS(){
try{
rs=stm.executeQuery(sql);
Object[] row=new Object[2];
 DefaultTableModel model=new DefaultTableModel(){
            private static final long serialVersionUID = 1L;  
             @Override
            public Class<?> getColumnClass(int column) {  
                    switch (column) {  
                        case 2: return Boolean.class;
                        default: return   String.class;
                                     }  
            }        
};
table.setModel(model);
model.setColumnIdentifiers(columNames);
while (rs.next()){
            for (int v=1;v<3;v++){
                    if(v==2){ row[2]=false; // or true..

                             } 
                    else{ row[v-1]=rs.getObject(v); }     
            }
            model.addRow(row);            
}//while
rs.close();
 }//try
 catch (SQLException e) { System.out.println(e); }           
 }

I did that, it works

Answer 2

Be certain to add values of type Boolean.class to your TableModel, as shown here. See also Creating a Table Model for a typical implementation.

@Override
public Class<?> getColumnClass(int c) {
    return getValueAt(0, c).getClass();
}

Addendum: I changed row value as true.

There are several ways to ensure that the model contains a value of type Boolean.class:

• Boolean.TRUE or Boolean.FLASE, constants defined in java.lang.Boolean.

• Boolean.valueOf(boolean b), where b may be a value or expression yielding boolean.

• true or false, literals that are autoboxed since Java 1.5.

As @kleopatra notes, the simple tutorial implementation fails to meet two essential critera:

• Guard against null values.

• Return the same value for the lifetime of the model.