比如有一个数据表user,它有id,parentid,name字段,
我现在写个bean,但是使用这个类的add方法的时候用不了,是什么原因呢??public class User {
private int ID;
private String Name;
private int parentID;
private ArrayList children;
public void setID(int i)
{
ID = i;
} public int getID()
{
return ID;
} public void setParentID(int i)
{
parentID = i;
} public int getParentID()
{
return parentID;
} public void setName(String s)
{
Name = s;
} public String getName()
{
return Name;
}
public ArrayList getChildren() {
return children;
} public void setChildren(ArrayList children) {
this.children = children;
}
public void add(User user) {
children.add(user);
}
}
我现在写个bean,但是使用这个类的add方法的时候用不了,是什么原因呢??public class User {
private int ID;
private String Name;
private int parentID;
private ArrayList children;
public void setID(int i)
{
ID = i;
} public int getID()
{
return ID;
} public void setParentID(int i)
{
parentID = i;
} public int getParentID()
{
return parentID;
} public void setName(String s)
{
Name = s;
} public String getName()
{
return Name;
}
public ArrayList getChildren() {
return children;
} public void setChildren(ArrayList children) {
this.children = children;
}
public void add(User user) {
children.add(user);
}
}
在User 的构造函数里加上children = new ArrayList();或者在声明的时候就写
private ArrayList children=new ArrayList();