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Java Collections - Collections.unmodifiableSortedMap() Examples

Java Collections Java Java API 

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Class:

java.util.Collections

java.lang.Objectjava.lang.Objectjava.util.Collectionsjava.util.CollectionsLogicBig

Method:

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

Returns an unmodifiable view of the specified SortedMap. Attempts to modify the returned SortedMap, whether direct or via its collection views or subMap/headMap/tailMap, will result in an UnsupportedOperationException.


Examples


Since the SortedMap created by this method is a view of the original map, modifying the original will reflect the changes in it: 

package com.logicbig.example.collections;

import java.util.Collections;
import java.util.SortedMap;
import java.util.TreeMap;

public class UnmodifiableSortedMapExample {

    public static void main(String... args) {
        SortedMap<Integer, String> map = new TreeMap<>();
        map.put(1, "one");
        map.put(2, "two");
        System.out.println("Original Map: " + map);
        SortedMap<Integer, String> map2 = Collections.unmodifiableSortedMap(map);
        System.out.println("unmodifiableSortedMap: " + map2);
        //modifying the original one
        map.remove(2);
        System.out.println("unmodifiableSortedMap: " + map2);
    }
}

Output

Original Map: {1=one, 2=two}
unmodifiableSortedMap: {1=one, 2=two}
unmodifiableSortedMap: {1=one}




Modifying itself will throw the exception:

package com.logicbig.example.collections;

import java.util.*;

public class UnmodifiableSortedMapExample2 {

    public static void main(String... args) {
        SortedMap<Integer, String> map = new TreeMap<>();
        map.put(1, "one");
        map.put(2, "two");
        System.out.println("Original Map: " + map);
        SortedMap<Integer, String> map2 = Collections.unmodifiableSortedMap(map);
        map2.remove(1);
    }
}

Output

Caused by: java.lang.UnsupportedOperationException
	at java.base/java.util.Collections$UnmodifiableMap.remove(Collections.java:1456)
	at com.logicbig.example.collections.UnmodifiableSortedMapExample2.main(UnmodifiableSortedMapExample2.java:19)
	... 6 more

See Also