java list去重,分組將數據存入map中了，list,array轉換

 

查找ArrayList中的重複的String,而後將string加入到list中，去重

 

ArrayList<String> result = new ArrayList<String>();

 

for(String s: sources){

    if(Collections.frequency(reslut, s) < 1) result.add(s);

}

 

 

 

怎麼樣對一個list中的對象經過對象中相同屬性進行分組,放到map中用於頁面顯示

分享| 2011-08-10 20:04 s11ag | 瀏覽 3971 次

軟件編程語言

舉報| 2011-08-10 20:19

提問者採納

Map<String,List> map = new HashMap<String,List>();
List list = new ArrayList();
for(int i=0;i<list.size();i++){
   User user = (User)list.get(i);
  String name =  user.getName();
  if(map.containsKey(name)){
     map.get(name).add(user);
 }else{
   List l = new ArrayList();
   l.add(user);
  map.put(name,user);
}
}

 

Java List與數組之間的轉換

標籤： javaJavaJAVAlistListLIST數組

2012-12-27 17:36 43168人閱讀 評論(0) 收藏 舉報

分類：

Java（35）

版權聲明：本文爲博主原創文章，未經博主容許不得轉載。

目錄(?)[+]

1 數組轉換爲List

調用Arrays類的靜態方法asList。

asList

public static <T> List<T> asList(T... a)

Returns a fixed-size list backed by the specified array. (Changes to the returned list "write through" to the array.) This method acts as bridge between array-based and collection-based APIs, in combination with Collection.toArray(). The returned list is serializable and implements RandomAccess.

This method also provides a convenient way to create a fixed-size list initialized to contain several elements:

     List<String> stooges = Arrays.asList("Larry", "Moe", "Curly");

Parameters:

a - the array by which the list will be backed

Returns:

a list view of the specified array

用法：API中提供了一種使用的方法。更爲經常使用的示例代碼：

[java] view plain copy

1. String[] arr = new String[] {"str1", "str2"};  
2. List<String> list = Arrays.asList(arr);  

2 List轉換爲數組

這裏的List以ArrayList爲例，ArrayList的API提供了兩種可供使用的函數。

toArray

public Object[] toArray()

Returns an array containing all of the elements in this list in proper sequence (from first to last element).

The returned array will be "safe" in that no references to it are maintained by this list. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.

This method acts as bridge between array-based and collection-based APIs.

Specified by:

toArray in interface Collection<E>

Specified by:

toArray in interface List<E>

Overrides:

toArray in class AbstractCollection<E>

Returns:

an array containing all of the elements in this list in proper sequence

See Also:

Arrays.asList(Object[])

toArray

public <T> T[] toArray(T[] a)

Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. If the list fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this list.

If the list fits in the specified array with room to spare (i.e., the array has more elements than the list), the element in the array immediately following the end of the collection is set to null. (This is useful in determining the length of the list only if the caller knows that the list does not contain any null elements.)

Specified by:

toArray in interface Collection<E>

Specified by:

toArray in interface List<E>

Overrides:

toArray in class AbstractCollection<E>

Parameters:

a - the array into which the elements of the list are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.

Returns:

an array containing the elements of the list

Throws:

ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this list

NullPointerException - if the specified array is null

用法：示例代碼：

[java] view plain copy

1. List<String> list = new ArrayList<String>();  
2. list.add("str1");  
3. list.add("str2");  
4. int size = list.size();  
5. String[] arr = (String[])list.toArray(new String[size]);//使用了第二種接口，返回值和參數均爲結果  

 

 

 

 

替換時注意轉意

         String html = sb.toString().replaceAll("\\{0\\}", "");