Problem Solved:
new code:
public Component getTableCellEditorComponent(JTable table, Object value,
	boolean isSelected, int row, int column)
	{
		tf = new JTextField();
		tf.setText(value.toString());
				
		return tf;
		
	}
Also--> 

public Object getCellEditorValue()
	{
		return new Float(tf.getText());
	
	}