数据读到了 但是怎么放在数组里面,?import java.sql.*; public class hava { final static String classname="com.microsoft.sqlserver.jdbc.SQLServerDriver"; final static String getconnection="jdbc:sqlserver://localhost:1433;databaseName=Hospital;user=sa;password=sasa"; public static final String sq="select * from use_login"; public static final String[] columnNames ={"name","position"};
public static void main(String args[]){ try{ Class.forName(classname); con=DriverManager.getConnection(getconnection);
但是有个 我想创建个 Jtable,数据是数据库表中的书上说 There are two JTable constructors that directly accept data (SimpleTableDemo uses the first):JTable(Object[][] rowData, Object[] columnNames) JTable(Vector rowData, Vector columnNames) 那我怎么办?
为什么抛出异常呢,我初学java不要BS我啊! null java.lang.NullPointerException at hava.main(hava.java:16)import java.sql.*; public class hava { public static final String sq="select * from use_login"; public static final String[] columnNames ={"name","position"}; static Statement stmt; static Object data[][]; public static void main(String args[]){ try{ ConnectionSQL.connect(); stmt=ConnectionSQL.con.createStatement(); ResultSet rs=stmt.executeQuery(sq); int i=0; while(rs.next()){ data[i][0]=rs.getString("name"); data[i][1]=rs.getString("position"); i++;
public class hava {
final static String classname="com.microsoft.sqlserver.jdbc.SQLServerDriver";
final static String
getconnection="jdbc:sqlserver://localhost:1433;databaseName=Hospital;user=sa;password=sasa";
public static final String sq="select * from use_login";
public static final String[] columnNames ={"name","position"};
public static void main(String args[]){
try{
Class.forName(classname);
con=DriverManager.getConnection(getconnection);
Statement stmt=con.createStatement();
ResultSet rs=stmt.executeQuery(sq);
while(rs.next()){
System.out.print(rs.getString("name"));
System.out.print(" ");
System.out.println(rs.getString("position"));
}
// System.out.println(data);
}
catch(Exception e ){
e.printStackTrace();
}怎么把rs.getString("name")这些放在数组二维的
如果你坚持数组的话,就声明数组为结果集的大小那么大,之后遍历,存放数据即可
JTable(Vector rowData, Vector columnNames) 那我怎么办?
null
java.lang.NullPointerException
at hava.main(hava.java:16)import java.sql.*;
public class hava {
public static final String sq="select * from use_login";
public static final String[] columnNames ={"name","position"};
static Statement stmt;
static Object data[][];
public static void main(String args[]){
try{
ConnectionSQL.connect();
stmt=ConnectionSQL.con.createStatement();
ResultSet rs=stmt.executeQuery(sq);
int i=0;
while(rs.next()){
data[i][0]=rs.getString("name");
data[i][1]=rs.getString("position");
i++;
}
}
catch(Exception e ){
e.printStackTrace();
}
System.out.println(data);
}
}
应为你声明的data[][]为Object类的二维数组。在你的while循环中没有对它初始化。Object类是一个引用类型。
引用类的new过程就是向内存申请空间的过程。你没有new(即:初始化)内存中没有你这个变量的地址。使用的时候当
然会报空指针异常。