//这样试一试
package DB;
import java.util.*;
import java.sql.*;
public class Data
{
///////////////////////
Connection Conn = null;
Statement St = null;
ResultSet Rs = null;
///////////////////////
HashMap BookHmap = null;
ArrayList ArrL = null;
Iterator i = null;
//////////////////////
BookDetails book = null;
public static void main(String args[]) {
try
{
Data d=new Data();
d.getAllBooks();
Collection c=d.BookArray();
Iterator i=c.iterator();
while(i.hasNext())
{
System.out.println("1");
}
}
catch (Exception e)
{
System.out.println(e.getMessage());
}
} public Collection BookArray() {
return ArrL;
} public void getAllBooks() {
try {
String query = "select * from booktable";
Class.forName("oracle.jdbc.driver.OracleDriver");
Conn = DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:SUN",
"scott", "tiger");
St = Conn.createStatement();
Rs = St.executeQuery(query);
/******************************************
HashMap BookHmap=new HashMap();
*******************************************/
BookHmap=new HashMap(); if (Conn != null && St != null && Rs != null)
{/////////////////////
测试过 while (Rs.next())
{
数据可 System.out.println(Rs.getString(1));
以取出 }/////////////////////////
while(Rs.next())
{
BookDetails book = new BookDetails(Rs.getString("BOOKID"),
Rs.getString("bookname"),
Rs.getString("BOOKSORT"),
Rs.getInt("bookprice"),
Rs.getInt("BOOKTOTAL"));
BookHmap.put(Rs.getString("BOOKID"), book);
}
/******************************************************************
ArrayList ArrL = new ArrayList(BookHmap.values());
*******************************************************************/
ArrL = new ArrayList(BookHmap.values());
Collections.sort(ArrL);
}
else {
System.out.println("Sql is null");
}
}
catch (ClassNotFoundException e) {}
catch (SQLException e) {}
}
}
package DB;
import java.util.*;
import java.sql.*;
public class Data
{
///////////////////////
Connection Conn = null;
Statement St = null;
ResultSet Rs = null;
///////////////////////
HashMap BookHmap = null;
ArrayList ArrL = null;
Iterator i = null;
//////////////////////
BookDetails book = null;
public static void main(String args[]) {
try
{
Data d=new Data();
d.getAllBooks();
Collection c=d.BookArray();
Iterator i=c.iterator();
while(i.hasNext())
{
System.out.println("1");
}
}
catch (Exception e)
{
System.out.println(e.getMessage());
}
} public Collection BookArray() {
return ArrL;
} public void getAllBooks() {
try {
String query = "select * from booktable";
Class.forName("oracle.jdbc.driver.OracleDriver");
Conn = DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:SUN",
"scott", "tiger");
St = Conn.createStatement();
Rs = St.executeQuery(query);
/******************************************
HashMap BookHmap=new HashMap();
*******************************************/
BookHmap=new HashMap(); if (Conn != null && St != null && Rs != null)
{/////////////////////
测试过 while (Rs.next())
{
数据可 System.out.println(Rs.getString(1));
以取出 }/////////////////////////
while(Rs.next())
{
BookDetails book = new BookDetails(Rs.getString("BOOKID"),
Rs.getString("bookname"),
Rs.getString("BOOKSORT"),
Rs.getInt("bookprice"),
Rs.getInt("BOOKTOTAL"));
BookHmap.put(Rs.getString("BOOKID"), book);
}
/******************************************************************
ArrayList ArrL = new ArrayList(BookHmap.values());
*******************************************************************/
ArrL = new ArrayList(BookHmap.values());
Collections.sort(ArrL);
}
else {
System.out.println("Sql is null");
}
}
catch (ClassNotFoundException e) {}
catch (SQLException e) {}
}
}
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你的getter是这样写的:
<<
public Collection BookArray() {
return ArrL;
}
>>
而生成ArrayList的语句是这样:
<<
ArrayList ArrL = new ArrayList(BookHmap.values());
>>
这两个ArrL是一个吗??
你的Arrl 重复定义了...
ArrayList ArrL = new ArrayList(BookHmap.values());
是你期待返回的Arrl,
但是,你前面定义的是:
ArrayList ArrL = null;
//.....
public Collection BookArray() {
return ArrL;
}
//.....
//这里你返回的Arrl当然是Null啦!