遇到 ExceptionInInitializerError 怎么解决？java报错

遇到 ExceptionInInitializerError 怎么解决？java报错

在编写java的样例代码时出现这种问题。这种情况应该如何解决和避免那？

package com.lang.ininitialException;
 
import java.util.ArrayList;
import java.util.List;
 
public class StaticParamsSingle {
 
  private static StaticParamsSingle sps = buildStaticParams();
//  private static StaticParamsSingle sps = new StaticParamsSingle();
  private static int NUM_A = getA();
  private static int NUM_B = getB();
  private static List<String> LIST_A = getListA();
   
  private StaticParamsSingle(){
    System.out.println("初始化构造方法");
  }
   
  private static StaticParamsSingle buildStaticParams() {
    if (sps == null) {
      sps = new StaticParamsSingle();
    }
     
    int result = NUM_A + NUM_B;
    System.out.println("result is:" + result);
    LIST_A.add("haha");
    return sps;
  }
   
  public static StaticParamsSingle getInstance() {
    return sps;
  }
   
  private static int getA(){
    System.out.println("初始化A");
    return 5;
  }
   
  private static int getB() {
    System.out.println("初始化B");
    return 10;
  }
   
  private static List<String> getListA() {
    System.out.println("初始化List");
    return new ArrayList<String>();
  }
   
  public static void main(String args[]) {
    StaticParamsSingle.getInstance();
     
  }
}

错误信息：

Exception in thread "main" java.lang.ExceptionInInitializerError
Caused by: java.lang.NullPointerException
    at com.lang.ininitialException.StaticParamsSingle.buildStaticParams(StaticParamsSingle.java:25)
    at com.lang.ininitialException.StaticParamsSingle.<clinit>(StaticParamsSingle.java:8)

原因是什么，为什么会发生异常，以及下面到底发生了什么。如果有人能帮忙？提前谢谢