集合類unmodifiableCollection()方法 (Collections Class unmodifiableCollection() method)

• unmodifiableCollection() method is available in java.util package.

  unmodifiableCollection()方法在java.util包中可用。

• unmodifiableCollection() method is used to get an unmodifiable view of the given collection and when we try to update the given collection then we will get an exception UnsupportedOperationException.

  unmodifiableCollection()方法用于獲取給定集合的不可修改視圖，當我們嘗試更新給定集合時，我們將獲得異常UnsupportedOperationException。

• unmodifiableCollection() method is a static method, it is accessible with the class name and if we try to access the method with the class object then also we will not get any error.

  unmodifiableCollection()方法是一個靜態方法，可以使用類名進行訪問，并且如果我們嘗試使用類對象訪問該方法，那么我們也不會收到任何錯誤。

• unmodifiableCollection() method may throw an exception at the time of modifying the given collection.

  unmodifiableCollection()方法在修改給定集合時可能會引發異常。

  UnsupportedOperationException: This exception may throw when we try to modify the given collection.

  UnsupportedOperationException ：當我們嘗試修改給定的集合時，可能會拋出此異常。

Syntax:

句法：

    public static Collection unmodifiableCollection(Collection co);

Parameter(s):

參數：

• Collection co – represents the collection object for which a non-modifiable view is to be retrieved.

  集合co –表示要檢索其不可修改視圖的集合對象。

Return value:

返回值：

The return type of this method is Collection, it returns an unmodifiable view of the given collection.

該方法的返回類型為Collection ，它返回給定集合的不可修改的視圖。

Example:

例：

// Java program to demonstrate the example 
// of Collection unmodifiableCollection()
// method of Collections
import java.util.*;
public class UnmodifiableCollectionOfCollections {
public static void main(String args[]) {
// Instatiates an array list object
List < Integer > arr_l = new ArrayList < Integer > ();
// By using add() method is to add
// objects in an array list 
arr_l.add(10);
arr_l.add(20);
arr_l.add(30);
arr_l.add(40);
arr_l.add(50);
// Display ArrayList
System.out.println("Array List: " + arr_l);
// By using unmodifiableCollection() method is to
// represent the array list in an unmodifiable view
Collection co = Collections.unmodifiableCollection(arr_l);
// We will get an exception if we 
// try to add an element in an unmodifiable
// collection
/* co.add(60); */
}
}

Output

輸出量

Array List: [10, 20, 30, 40, 50]

翻譯自: https://www.includehelp.com/java/collections-unmodifiablecollection-method-with-example.aspx