Java System.NullPointerException:尝试反引用null对象

请帮我写代码，我是Java/SF新手，我不理解整个代码

下面的代码应返回18岁以下、18至30岁及以上人群的三个值

我想学习的编码和我的意见，所有的行，如果有什么错误，请纠正我

在我得到错误的那一刻：

System.NullPointerException:尝试反引用null对象

Class.testfor1_c.getEZRen：第18行第1列 类。testfor1_c.：第4行第1列

public class testfor1_c {

public testfor1_c(ApexPages.StandardController stdcontroller) { 
    getEZRen();
}

public Integer Count_u18 {get; set;} // variable for people < 18
public Integer Count_1830 {get; set;} // variable for people >=18 AND <30
public Integer Count_g30 {get; set;} // variable for people >30

public void getEZRen() {

List<Einzelrisiko__c> EZRList = [SELECT Alter__c FROM Einzelrisiko__c]; // create List EZRList with the information Alter__c of all people

FOR (Einzelrisiko__c EZR : EZRList) {  // Loop thru the all people

    IF(EZR.Alter__c < 18) { Count_u18++; } // if Alter__c < 18 variable Count_u18 increase
    IF(EZR.Alter__c >= 18 && EZR.Alter__c <=30) { Count_1830++; } // if Alter__c >=18 AND <=30 variable Count_1830 increase
    IF(EZR.Alter__c > 30) { Count_g30++; } // if Alter__c > 30 variable Count_g30 increase

}

}

}

<apex:page standardcontroller="account" extensions="testfor1_c">

Anzahl {!Count_u18} // show the value of people <18
Anzahl {!Count_1830} // show the value of people >=18 AND <=30
Anzahl {!Count_g30} // show the value of people >30

</apex:page>

提前感谢,，

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peX

IFEZR.Alter\uuu c>=18&&EZR.Alter\uu c您只需要初始化整数属性

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希望它能帮助你

好的，你说支票是什么意思？我是Java和Salesforce的新手。这意味着EZR.Alter__;c在某个时候为null，你必须检查它是否为null。就像你可以使用ifEZR.Alter_u_;c=null用于在出现null值时执行操作----通过此链接，在调试模式下运行代码一次。我仍然得到错误，请查看下面我的帖子。

public class testfor1_c {

      public testfor1_c(ApexPages.StandardController stdcontroller) { 
          Count_u18 = 0;
          Count_1830 = 0;
          Count_g30 = 0;
          getEZRen();
      }

      public Integer Count_u18 {get; set;} // variable for people < 18
      public Integer Count_1830 {get; set;} // variable for people >=18 AND <30
      public Integer Count_g30 {get; set;} // variable for people >30

      public void getEZRen() {

         List<Einzelrisiko__c> EZRList = [SELECT Alter__c FROM Einzelrisiko__c]; // create List EZRList with the information Alter__c of all people

         for(Einzelrisiko__c EZR : EZRList) {  // Loop thru the all people

               IF(EZR.Alter__c < 18) { Count_u18++; } // if Alter__c < 18 variable Count_u18 increase
               IF(EZR.Alter__c >= 18 && EZR.Alter__c <=30) { Count_1830++; } // if Alter__c >=18 AND <=30 variable Count_1830 increase
              IF(EZR.Alter__c > 30) { Count_g30++; } // if Alter__c > 30 variable Count_g30 increase
         }
      }
}