Java Collections unmodifiableSortedMap()用法及代碼示例

java.util.Collections類的unmodifiableSortedMap()方法用於返回指定的已排序映射的不可修改視圖。此方法允許模塊為用戶提供對內部排序映射的隻讀訪問權限。對返回的排序圖“read through”到指定排序圖的查詢操作。嘗試通過其集合視圖或通過其subMap，headMap或tailMap視圖直接修改返回的已排序Map會導致UnsupportedOperationException。

如果指定的排序圖可序列化，則返回的排序圖將可序列化。

用法:

public static <K, V> SortedMap<K, V>
    unmodifiableSortedMap(SortedMap<K, ? extends V> m)

參數：此方法將已排序的映射作為參數，要為其返回不可修改的視圖。

返回值：此方法返回指定排序映射的不可修改視圖。

以下示例說明了unmodifiableSortedMap()方法

示例1:

// Java program to demonstrate 
// unmodifiableSortedMap() method 
// for <String, String> value 
  
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) 
        throws Exception 
    { 
  
        try { 
  
            // creating object of SortedMap<String, String> 
            SortedMap<String, String> 
                map = new TreeMap<String, String>(); 
  
            // populate the map 
            map.put("First", "10"); 
            map.put("Second", "20"); 
            map.put("Third", "30"); 
  
            // make the map unmodifiable 
            Map<String, String> 
                unmodsortmap = Collections 
                                   .unmodifiableSortedMap(map); 
  
            // printing unmodifiablemap 
            System.out.println("Initial sorted map value: "
                               + map); 
        } 
  
        catch (UnsupportedOperationException e) { 
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

輸出：

Initial sorted map value: {First=10, Second=20, Third=30}

示例2:對於UnsupportedOperationException

// Java program to demonstrate 
// unmodifiableSortedMap() method 
// For UnsupportedOperationException 
  
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) throws Exception 
    { 
  
        try { 
  
            // creating object of SortedMap<String, String> 
            SortedMap<String, String> 
                map = new TreeMap<String, String>(); 
  
            // populate the map 
            map.put("First", "10"); 
            map.put("Second", "20"); 
            map.put("Third", "30"); 
  
            // make the map unmodifiable 
            Map<String, String> 
                unmodsortmap = Collections 
                                   .unmodifiableSortedMap(map); 
  
            // printing unmodifiablemap 
            System.out.println("unmodifiableSortedMap value: "
                               + map); 
  
            System.out.println("\nTrying to modify"
                               + " the unmodifiable SortedMap"); 
            unmodsortmap.put("Forth", "40"); 
        } 
  
        catch (UnsupportedOperationException e) { 
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

輸出：

unmodifiableSortedMap value: {First=10, Second=20, Third=30}

Trying to modify the unmodifiable SortedMap
Exception thrown : java.lang.UnsupportedOperationException

相關用法

注：本文由純淨天空篩選整理自RohitPrasad3大神的英文原創作品 Collections unmodifiableSortedMap() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。