Java集合unmodifiableMap()方法及示例

集合类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()方法用于获取给定Map(地图)的不可修改视图。

  • 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()方法是一个静态方法,可以使用类名进行访问,如果尝试使用类对象访问该方法,那么也不会出现任何错误。

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

    返回给定地图的不可修改视图时, unmodifiableMap()方法不会引发异常。

Syntax:

句法:

    public static Map unmodifiableMap(Map map);

Parameter(s):

参数:

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

    地图地图 –代表要检索其不可修改视图的地图对象。

Return value:

返回值:

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

此方法的返回类型为Map ,它返回给定map的不可修改视图。

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

输出量

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


翻译自: https://www.includehelp.com/java/collections-unmodifiablemap-method-with-example.aspx

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