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