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Java Collections - Collections.unmodifiableNavigableMap() 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> NavigableMap<K,V> unmodifiableNavigableMap(NavigableMap<K,? extends V> m)

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


Examples


Since the NavigableMap 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.NavigableMap;
import java.util.TreeMap;

public class UnmodifiableNavigableMapExample {

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

Output

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




Modifying itself will throw the exception:

package com.logicbig.example.collections;

import java.util.Collections;
import java.util.NavigableMap;
import java.util.TreeMap;

public class UnmodifiableNavigableMapExample2 {

    public static void main(String... args) {
        NavigableMap<Integer, String> map = new TreeMap<>() {};
        map.put(1, "one");
        map.put(2, "two");
        NavigableMap<Integer, String> map2 = Collections.unmodifiableNavigableMap(map);
        map2.put(3, "three");
    }
}

Output

Caused by: java.lang.UnsupportedOperationException
	at java.base/java.util.Collections$UnmodifiableMap.put(Collections.java:1453)
	at com.logicbig.example.collections.UnmodifiableNavigableMapExample2.main(UnmodifiableNavigableMapExample2.java:20)
	... 6 more

See Also