读取数据库写入数组
package list;



import java.io.File;


import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.sql.*;

import java.util.ArrayList;
import java.util.List;


public class ConnOracle {



private static Statement connc;
private static Connection connOrac;

//就差把它搞到数组里了

public static void main(String args[]) throws IOException{

try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
connOrac = DriverManager.getConnection("jdbc:mysql://localhost/ip?user=root&password=1314521&useUnicode=true&characterEncoding=gb2312");
connc=connOrac.createStatement();
System.out.println("ok1");
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");


} catch (Exception e) {
e.printStackTrace();
}


List<String> userName = new ArrayList<String>();
String sql="SELECT SUBSTRING(startip,1,9),startip,endip FROM ip WHERE country LIKE '广东%' GROUP BY SUBSTRING(startip,1,9) HAVING COUNT(*)>3 " ;




try {
ResultSet rs = connc.executeQuery(sql);
// int i = 0;
// int rowCount = rs.getRow();//首先将指针移动到最后一条记录，获得总记录数
String[] tastr = new String[rs.getRow()];
int i=0;

for (rs.next() ){
tastr[i] = rs.getString(1);
tastr[i+1] = rs.getString(2);
tastr[i+2] = rs.getString(3);
tastr[i+3] = rs.getString(4);
i++;


File f = new File("D:"+File.separator+"testfile.txt");
//用FileOutputSteam包装文件，并设置文件可追加
OutputStream out;
try {
out = new FileOutputStream(f,true);

out.write(tastr[i+2].getBytes()); //向文件中写入数据
out.write('\r'); // \r\n表示换行
out.write('\n');

out.close();//关闭输出流
System.out.println("写入成功！");



} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}





}












} catch (SQLException ex) {
System.out.println(ex);
}
// TODO Auto-generated catch block


}



}







[解决办法]
个人觉得应该这样吧：

Java code

        OutputStream out = null;        try {            ResultSet rs = connc.executeQuery(sql);            String[][] datas = new String[rs.getRow()][4];                        int i = 0;            while (rs.next()) {                datas[i][0] = rs.getString(1);                datas[i][1] = rs.getString(1);                datas[i][2] = rs.getString(1);                datas[i][3] = rs.getString(1);                i++;            }            for(String[] data : datas){                for(String d : data){                    File f = new File("D:" + File.separator + "testfile.txt");                    // 用FileOutputSteam包装文件，并设置文件可追加                    out = new FileOutputStream(f, true);                    out.write(d.getBytes()); // 向文件中写入数据                }                out.write('\r'); // \r\n表示换行                out.write('\n');                System.out.println("写入成功！");            }        } catch (SQLException ex) {            System.out.println(ex);        } finally{            if(out != null) out.close();        }