java list去重,分组将数据存入map中了，list,array转换

 

查找ArrayList中的重复的String,而后将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);

}

 

 

 

怎么样对一个list中的对象经过对象中相同属性进行分组,放到map中用于页面显示

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

软件编程语言

举报| 2011-08-10 20:19

提问者采纳

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与数组之间的转换

标签： javaJavaJAVAlistListLIST数组

2012-12-27 17:36 43168人阅读 评论(0) 收藏 举报

分类：

Java（35）

版权声明：本文为博主原创文章，未经博主容许不得转载。

目录(?)[+]

1 数组转换为List

调用Arrays类的静态方法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中提供了一种使用的方法。更为经常使用的示例代码：

[java] view plain copy

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

2 List转换为数组

这里的List以ArrayList为例，ArrayList的API提供了两种可供使用的函数。

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：示例代码：

[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]);//使用了第二种接口，返回值和参数均为结果  

 

 

 

 

替换时注意转意

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