当我向子节点添加字符串时出现错误
public void createNode(int group){
DefaultMutableTreeNode root = null;
DefaultMutableTreeNode child[] = null;
List<String> list = new ArrayList<String>();
ExpressionBuilder builder=new ExpressionBuilder();
list = builder.getExpression(group,0);
root = new DefaultMutableTreeNode(groupString);
defaultTreeModel = new DefaultTreeModel(root);
for(int i=0; i<list.size();i++){
child[i] = new DefaultMutableTreeNode(list.get(i));
defaultTreeModel.insertNodeInto(child[i], root, i);
}
}
当我创建子数组时，它给了我空指针异常的错误。列表已正确填充。
public void createNode(int group){
DefaultMutableTreeNode root = null;
DefaultMutableTreeNode child[] = null;
List<String> list = new ArrayList<String>();
ExpressionBuilder builder=new ExpressionBuilder();
list = builder.getExpression(group,0);
root = new DefaultMutableTreeNode(groupString);
defaultTreeModel = new DefaultTreeModel(root);
for(int i=0; i<list.size();i++){
child[i] = new DefaultMutableTreeNode(list.get(i));
defaultTreeModel.insertNodeInto(child[i], root, i);
}
}
when i am making child array it is giving me error of null pointer exception. list is populated correctly.
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子数组为空。
创建数组时，您需要执行以下操作：
因此，您需要在创建列表后创建数组，以便知道数组的大小。
The child array is null.
When you create an array you need to do something like:
So you would need to create the array after you create the List so you know what size to make the array.