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

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

  unmodifiableMap()方法在java.util包中可用。

• unmodifiableMap() method is used to get a non-modifiable view of the given Map (map).

  unmodifiableMap()方法用于獲取給定Map(地圖)的不可修改視圖。

• unmodifiableMap() 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.

  unmodifiableMap()方法是一個靜態方法，可以使用類名進行訪問，如果嘗試使用類對象訪問該方法，那么也不會出現任何錯誤。

• unmodifiableMap() method does not throw an exception at the time of returning unmodifiable view of the given map.

  返回給定地圖的不可修改視圖時， unmodifiableMap()方法不會引發異常。

Syntax:

句法：

    public static Map unmodifiableMap(Map map);

Parameter(s):

參數：

• Map map – represents the map object for which a non-modifiable view is to be retrieved.

  地圖地圖 –代表要檢索其不可修改視圖的地圖對象。

Return value:

返回值：

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

此方法的返回類型為Map ，它返回給定map的不可修改視圖。

Example:

例：

// Java program to demonstrate the example 
// of Map unmodifiableMap() method of collections
import java.util.*;
public class UnmodifiableMapOfCollections {
public static void main(String args[]) {
// Instantiates a linked hashmap object
Map < Integer, String > lhm = new LinkedHashMap < Integer, String > ();
// By using put() method is to add
//objects in a linked hashmap 
lhm.put(10, "C");
lhm.put(20, "C++");
lhm.put(30, "JAVA");
lhm.put(40, "PHP");
lhm.put(50, "SFDC");
// Display Linked HashMap
System.out.println("linked hashmap: " + lhm);
// By using unmodifiableMap() method is to
// represent the linked hashmap in unmodifiable view
Map m = Collections.unmodifiableMap(lhm);
//We will get an exception when we
//try to add an object in an unmodifiable map
/* mm.put(60,"COBOL");*/
}
}

Output

輸出量

linked hashmap: {10=C, 20=C++, 30=JAVA, 40=PHP, 50=SFDC}

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