Java Collections unmodifiableCollection（）方法与示例

集合类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()方法用于获取给定集合的不可修改视图，当我们尝试更新给定集合时，我们将获得异常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()方法是一个静态方法，可以使用类名进行访问，并且如果我们尝试使用类对象访问该方法，那么我们也不会收到任何错误。
unmodifiableCollection() method may throw an exception at the time of modifying the given collection.
unmodifiableCollection()方法在修改给定集合时可能会引发异常。

UnsupportedOperationException: This exception may throw when we try to modify the given collection.
UnsupportedOperationException ：当我们尝试修改给定的集合时，可能会抛出此异常。

Syntax:

句法：

    public static Collection unmodifiableCollection(Collection co);

Parameter(s):

参数：

Collection co – represents the collection object for which a non-modifiable view is to be retrieved.
集合co –表示要检索其不可修改视图的集合对象。

Return value:

返回值：

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

该方法的返回类型为Collection ，它返回给定集合的不可修改的视图。

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

输出量