java实现多字段sql分组

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;


public class Java_group_sql {
  public static final Object[] arr1=new Object[]{"11","22","33","44","55"};
  public static final Object[] arr2=new Object[]{"22","22","33","44","55"};
  public static final Object[] arr3=new Object[]{"33","22","33","44","55"};
  public static final Object[] arr4=new Object[]{"44","22","33","44","55"};
  public static final Object[] arr5=new Object[]{"11","22","33","44","55"};
  public static final Object[] arr6=new Object[]{"11","22","33","44","55"};
/**
  * list要分组的数据（数据中查询出或者其他）
  * @param list
  * @param idx 按照具体字段进行分组（idx是数组的下标）
   * @return
  */
  public static List<List<Object[]>> group(List<Object[]> list,int idx){
  Map<Object,List<Object[]>> map=new HashMap<Object, List<Object[]>>();
  for (int i = 0; i < list.size(); i++) {
List<Object[]> temp=null;
List<Object[]> value=(List<Object[]>)map.get(list.get(i)[idx].toString());
if(value==null){
temp=new ArrayList<Object[]>();
temp.add(list.get(i));
map.put(list.get(i)[idx].toString(), temp);
}else{
temp=(List<Object[]>)map.get(list.get(i)[idx].toString());
temp.add(list.get(i));
map.put(list.get(i)[idx].toString(), temp);
}
}
Iterator it=map.keySet().iterator();
List<List<Object[]>> resList=new ArrayList<List<Object[]>>();
Object key=null;
while(it.hasNext()){
key=it.next();
if(key!=null){
resList.add(map.get(key));
}
}
  return resList;
  }
  //测试
  public static void main(String[] args) {
List<Object[]> list=new ArrayList<Object[]>();
list.add(arr1);
list.add(arr2);
list.add(arr3);
list.add(arr4);
list.add(arr5);
list.add(arr6);
List<List<Object[]>> resList=group(list,0);
for (int i = 0; i < resList.size(); i++) {
List<Object[]> inner=resList.get(i);
System.out.println("==============");
for (int j = 0; j < inner.size(); j++) {
Object[] obj=inner.get(j);
System.out.println("["+obj[0]+","+obj[1]+","+obj[2]+","+obj[3]+"]");
}
}

}
}