Question

怎么输出List中的每个元素

package com.huayu.oper;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.huayu.db.DBConnection;
import com.huayu.impl.ProductInterface;
import com.huayu.voo.Product;

public class ProductOperate implements ProductInterface {
ArrayList a = new ArrayList();
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
String sql = null;
DBConnection dbcn = new DBConnection();
Product p = new Product();

public ArrayList SelectAll() {

try {
sql = "select productid,productname,unitprice from products";
conn = dbcn.getConn2000();
int n = 0;

ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while (rs.next()) {

p.setProductid(rs.getInt(1));
p.setProductname(rs.getString(2));
p.setUnitprice(rs.getFloat(3));
a.add(p);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (ps != null) {
try {
ps.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}
return a;
}
public static void main(String[] args) {
ProductOperate po=new ProductOperate();
Product p=new Product();
List l=po.SelectAll();
for (int i = 0; i < l.size(); i++) {
p=(Product)l.get(i);
System.out.println(p.getProductid()+"\t"+p.getProductname()+"\t"+p.getUnitprice());
}
}
}
一直输出77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
77 Original Frankfurter grüne So?e 13.0
怎么解决

Answer 1

p.setProductid(rs.getInt(1));
p.setProductname(rs.getString(2));
p.setUnitprice(rs.getFloat(3));

可能是rs.getInt rs.getString的问题。后面的参数为数据库表对应的列名，你并没有用占位符，1 2 3 没有意义的吧。。

Answer 2

for（int i=0；i<list.cout;i++）
{
}