java 静态数组的问题

Question

package com.hwua.template;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.hwua.domain.Account;import com.hwua.tools.DBHelper;public class TestTemplate<T> { public static void main(String[] args) { List<Account> list = tt.testQuery("select * from t_account", new ResultSetHandler<List<Account>>() { @Override public List<Account> handler(ResultSet rSet) { List<Account> list = new ArrayList<>(); try { while (rSet.next()) { Account a = new Account(); a.setAccountId(rSet.getInt("t_id")); a.setAccountName(rSet.getString("t_name")); a.setAccountBalance(rSet.getInt("t_money")); list.add(a); } } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return list; } }); if (list != null) { for (Account account : list) { System.out.println(account); } } } public void updateSQL(String sql,Object...params) { try { Connection conn = DBHelper.getInstance().getConnection(); conn.setAutoCommit(true); PreparedStatement pStatement = conn.prepareStatement(sql); int count = pStatement.getParameterMetaData().getParameterCount(); for (int i = 0; i < count; i++) { pStatement.setObject(i+1, params[i]); } pStatement.executeUpdate(); } catch (SQLException e) { e.printStackTrace(); } } /*** * 通过内部接口来提供一个结果集的持有者. * @author Administrator * * @param <T> */ interface ResultSetHandler<T>{ T handler(ResultSet rSet); } public T testQuery(String sql,ResultSetHandler<T> handler,Object...params) { try { Connection conn = DBHelper.getInstance().getConnection(); PreparedStatement pStatement = conn.prepareStatement(sql); int count = pStatement.getParameterMetaData().getParameterCount(); for (int i = 0; i < count; i++) { pStatement.setObject(i+1, params[i]); } ResultSet rSet= pStatement.executeQuery(); return handler.handler(rSet); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return null; }}public View showView(){ System.out.println("请输入你的账号"); String inputid = mScanner.next(); System.out.println("请输入您的密码"); String inputpassword = mScanner.next(); System.out.println(TestTemplate.list == null); for (Account a : TestTemplate.list) { if(inputid .equals(a.getAccount()) && inputpassword.equals(a.getPassword())) { return new UserView(); }else if (!(inputid.equals(a.getAccount()))){ System.out.println("账号不存在!"); return new MainView(); }else { System.out.println("账号或密码错误!"); return new MainView(); } } return mView;请问为什么我在TestTemplate中打印list数组就可以,把它声明成静态之后去LoginView调用打印进行匹配时报空指针呢 这两个不在同一个包里面