判斷List中的重複數據

1.
// 通過去重之後的HashSet長度來判斷原list是否包含重複元素
boolean isRepeat = list.size() != new HashSet<String>(list).size();
        System.out.println("list中包含重複元素：" + isRepeat);
        System.out.println("over");*/
		
2.
public static void same(List<String> list) {
        String [] indexArr ;
        Map<String, String> map = new HashMap<String, String>();
        for (int i = 0; i < list.size(); i++) {
            String key = list.get(i);
            String old = map.get(key);
            if (old != null) {
                map.put(key, old + "," + (i + 1));
            } else {
                map.put(key, "" + (i + 1));
            }
        }
        Iterator<String> it = map.keySet().iterator();
        int index = -1;
        while (it.hasNext()) {
            String key = it.next();
            String value = map.get(key);
            if (value.indexOf(",") != -1) {
                System.out.println(key + " 重複,行： " + value);
                indexArr = value.split(",");

                for (int i = 0; i < indexArr.length; i++) {
                    index = Integer.parseInt(indexArr[i])-1;
                    list.set(index, list.get(index)+(1+i));
                }
            }
        }

        for (String val : list) {
            System.out.println("val = "+val);
        }
        System.out.println("..................");

    }	
3.循環list中的所有元素然後刪除重複
public   static   List  removeDuplicate(List list)  {       
  for  ( int  i  =   0 ; i  <  list.size()  -   1 ; i ++ )  {       
      for  ( int  j  =  list.size()  -   1 ; j  >  i; j -- )  {       
           if  (list.get(j).equals(list.get(i)))  {       
              list.remove(j);       
            }        
        }        
      }        
    return list;       
}  	
4.通過HashSet踢除重複元素
public static List removeDuplicate(List list) {   
HashSet h = new HashSet(list);   
list.clear();   
list.addAll(h);   
return list;   
}   
5.
// 刪除ArrayList中重複元素，保持順序     
 public static void removeDuplicateWithOrder(List list) {    
    Set set = new HashSet();    
     List newList = new ArrayList();    
   for (Iterator iter = list.iterator(); iter.hasNext();) {    
         Object element = iter.next();    
         if (set.add(element))    
            newList.add(element);    
      }     
     list.clear();    
     list.addAll(newList);    
    System.out.println( " remove duplicate " + list);    
 }   
 
6.把list裏的對象遍歷一遍，用list.contain()，如果不存在就放入到另外一個list集合中
public static List removeDuplicate(List list){  
        List listTemp = new ArrayList();  
        for(int i=0;i<list.size();i++){  
            if(!listTemp.contains(list.get(i))){  
                listTemp.add(list.get(i));  
            }  
        }  
        return listTemp;  
    }