static public DefaultMutableTreeNode root = new DefaultMutableTreeNode("资产");
private JTree getJTree() {
if (jTree == null) {
DefaultMutableTreeNode [] Node = null;
db.dbconn();
int i = 1;
String sql = "select * from channel where class=1";
try{
rs = db.stmt.executeQuery(sql);
while(rs.next()){
i++;
Node[i] = new DefaultMutableTreeNode(rs.getString("channel"));
root.add(Node[i]);
}
rs.close();
} catch(Exception e){e.printStackTrace();}
db.closedb();
jTree = new JTree(root);
jTree.setEditable(true);
treeModel = (DefaultTreeModel) jTree.getModel();
}
return jTree;
}运行出现
java.lang.NullPointerException
at k.Property.getJTree(Property.java:139)错误行 Node[i] = new DefaultMutableTreeNode(rs.getString("channel"));
private JTree getJTree() {
if (jTree == null) {
DefaultMutableTreeNode [] Node = null;
db.dbconn();
int i = 1;
String sql = "select * from channel where class=1";
try{
rs = db.stmt.executeQuery(sql);
while(rs.next()){
i++;
Node[i] = new DefaultMutableTreeNode(rs.getString("channel"));
root.add(Node[i]);
}
rs.close();
} catch(Exception e){e.printStackTrace();}
db.closedb();
jTree = new JTree(root);
jTree.setEditable(true);
treeModel = (DefaultTreeModel) jTree.getModel();
}
return jTree;
}运行出现
java.lang.NullPointerException
at k.Property.getJTree(Property.java:139)错误行 Node[i] = new DefaultMutableTreeNode(rs.getString("channel"));
private JTree getJTree() {
if (jTree == null) {
db.dbconn();
int i = 1;
String sql = "select * from channel where class=1"; try{
rs = db.stmt.executeQuery(sql);
while(rs.next()){
i++;
DefaultMutableTreeNode node = new DefaultMutableTreeNode(rs.getString("channel"));
root.add(node);
}
rs.close();
} catch(Exception e){e.printStackTrace();}
db.closedb();
jTree = new JTree(root);
jTree.setEditable(true);
treeModel = (DefaultTreeModel) jTree.getModel();
}
return jTree;
}
private JTree getJTree() {
if (jTree == null) {
db.dbconn();
int i = 0,j=0;
String sql = "select * from channel where class=1";
try {
rs = db.stmt.executeQuery(sql);
while(rs.next()){
j++;
}
DefaultMutableTreeNode[] Note = new DefaultMutableTreeNode[j];
while (rs.next()) {
i++;
Note[i] = new DefaultMutableTreeNode(rs.getString("channel"));
root.add(Note[i]);
}
rs.close();
} catch (Exception e) {
e.printStackTrace();
}
db.closedb();
i++;
Note[i] = new DefaultMutableTreeNode(rs.getString("channel"));
root.add(Note[i]);
}
这个时个rs已经指到尾了,这个循环是不会执行的.
int i = 0, j = 0;
String sql = "select * from channel where class=1";
try {
rs = db.stmt.executeQuery(sql);
while (rs.next()) {
j = rs.getRow();
}
DefaultMutableTreeNode[] Note = new DefaultMutableTreeNode[j]; while (rs.next()) {
i++;
Note[i] = new DefaultMutableTreeNode(rs
.getString("channel"));
root.add(Note[i]);
} } catch (Exception e) {
e.printStackTrace();
} finally {
try {
rs.close();
rs = null;
} catch (SQLException k) {
}
}
db.closedb(); jTree = new JTree(root);
jTree.setEditable(true);这样也没结果,,怎么回事呢
rs = db.stmt.executeQuery(sql);
DefaultMutableTreeNode[] Note = new DefaultMutableTreeNode[rs.getRow()]; while (rs.next()) {
i++;
Note[i] = new DefaultMutableTreeNode(rs
.getString("channel"));
root.add(Note[i]);
} } catch (Exception e) {
e.printStackTrace();
} finally {
try {
rs.close();
rs = null;
} catch (SQLException k) {
}
}
原因同上