想实现一个功能，将1~12个数字分成四组，分别放入a，b,c,d中必须用Map<String,ArrayList<String>>这个结构，我想问一下该怎么写呢？如果要是分成六组呢，更多呢？
        public static void main(String[] args)
    {
        String[] array={"a","b","c","d"};
        
        int[] num = new int[12];
        Map<String,ArrayList<String>> map = new HashMap();
        for(int i=0;i<num.length;i++)
        {
            num[i]=i+1;
            //System.out.print(num[i]+" ");
        }
        for(int i=0;i<array.length;i++)
        {
            ArrayList list = new ArrayList();
            for(int j=0;j<num.length;j++)
            {
                if(num[j]<4)
                {
                    list.add(String.valueOf(num[j]));
                    continue;
                }
                else if(num[j]>=4&&num[j]<8)
                {
                    list.add(String.valueOf(num[j]));
                    continue;
                }
                else if(num[j]>=8&&num[j]<10)
                {
                    list.add(String.valueOf(num[j]));
                    continue;
                }
                    
                else
                {
                    list.add(String.valueOf(num[j]));
                    continue;
                }   
                    
                    
                    
            }
            map.put(array[i], list);
            
        }
        
        for(String key:map.keySet())
        {
            System.out.println(key+" "+map.get(key));
        }
        
    }