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Java Collections - Collections.unmodifiableNavigableSet() Examples

[Last Updated: Dec 11, 2025]

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 <T> NavigableSet<T> unmodifiableNavigableSet(NavigableSet<T> s)

Returns an unmodifiable view (read-only) of the specified NavigableSet. Attempts to modify the returned NavigableSet, whether direct or via its iterator or via subSet, headSet, or tailSet views , result in an UnsupportedOperationException.


Examples


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

package com.logicbig.example.collections;

import java.util.*;

public class UnmodifiableNavigableSetExample {

    public static void main(String... args) {
        NavigableSet<Integer> set = new TreeSet<>();
        Collections.addAll(set, 1, 4, 7);
        System.out.println("Original Set: " + set);

        NavigableSet<Integer> set2 = Collections.unmodifiableNavigableSet(set);
        System.out.println("unmodifiableNavigableSet: " + set2);
        //modifying the original
        set.add(10);
        System.out.println("unmodifiableNavigableSet: " + set2);
    }
}

Output

Original Set: [1, 4, 7]
unmodifiableNavigableSet: [1, 4, 7]
unmodifiableNavigableSet: [1, 4, 7, 10]
JDK 25




Modifying itself will throw exception:

package com.logicbig.example.collections;

import java.util.Collections;
import java.util.NavigableSet;
import java.util.TreeSet;

public class UnmodifiableNavigableSetExample2 {

    public static void main(String... args) {
        NavigableSet<Integer> set = new TreeSet<>();
        Collections.addAll(set, 1, 4, 7);
        System.out.println("Original Set: " + set);

        NavigableSet<Integer> set2 = Collections.unmodifiableNavigableSet(set);
        set2.add(10);
    }
}

Output

Original Set: [1, 4, 7]
java.lang.UnsupportedOperationException
    at java.util.Collections$UnmodifiableCollection.add (Collections.java:1093)
    at com.logicbig.example.collections.UnmodifiableNavigableSetExample2.main (UnmodifiableNavigableSetExample2.java:22)
    at jdk.internal.reflect.DirectMethodHandleAccessor.invoke (DirectMethodHandleAccessor.java:104)
    at java.lang.reflect.Method.invoke (Method.java:565)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.executeMainMethod (AbstractExecJavaBase.java:402)
    at org.codehaus.mojo.exec.ExecJavaMojo.executeMainMethod (ExecJavaMojo.java:142)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.doExecClassLoader (AbstractExecJavaBase.java:377)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.lambda$execute$0 (AbstractExecJavaBase.java:287)
    at java.lang.Thread.run (Thread.java:1474)
JDK 25




package com.logicbig.example.collections;

import java.util.Collections;
import java.util.NavigableSet;
import java.util.SortedSet;
import java.util.TreeSet;

public class UnmodifiableNavigableSetExample3 {

    public static void main(String... args) {
        NavigableSet<Integer> set = new TreeSet<>();
        Collections.addAll(set, 1, 3, 4, 7, 9, 11);
        System.out.println("Original Set: " + set);
        //headset of the original set
        SortedSet<Integer> headSet = set.headSet(4);

        NavigableSet<Integer> set2 = Collections.unmodifiableNavigableSet(set);
        System.out.println("unmodifiableNavigableSet: " + set2);
        //modifying headSet
        headSet.add(2);
        System.out.println("unmodifiableNavigableSet: " + set2);
        System.out.println("Original Set: " + set);
    }
}

Output

Original Set: [1, 3, 4, 7, 9, 11]
unmodifiableNavigableSet: [1, 3, 4, 7, 9, 11]
unmodifiableNavigableSet: [1, 2, 3, 4, 7, 9, 11]
Original Set: [1, 2, 3, 4, 7, 9, 11]
JDK 25




package com.logicbig.example.collections;

import java.util.Collections;
import java.util.NavigableSet;
import java.util.SortedSet;
import java.util.TreeSet;

public class UnmodifiableNavigableSetExample4 {

    public static void main(String... args) {
        NavigableSet<Integer> set = new TreeSet<>();
        Collections.addAll(set, 1, 3, 4, 7, 9, 11);
        System.out.println("Original Set: " + set);

        NavigableSet<Integer> set2 = Collections.unmodifiableNavigableSet(set);
        System.out.println("unmodifiableNavigableSet: " + set2);
        //headset of the unmodifiableNavigableSet
        SortedSet<Integer> headSet = set2.headSet(4);
        headSet.add(2);
    }
}

Output

Original Set: [1, 3, 4, 7, 9, 11]
unmodifiableNavigableSet: [1, 3, 4, 7, 9, 11]
java.lang.UnsupportedOperationException
    at java.util.Collections$UnmodifiableCollection.add (Collections.java:1093)
    at com.logicbig.example.collections.UnmodifiableNavigableSetExample4.main (UnmodifiableNavigableSetExample4.java:24)
    at jdk.internal.reflect.DirectMethodHandleAccessor.invoke (DirectMethodHandleAccessor.java:104)
    at java.lang.reflect.Method.invoke (Method.java:565)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.executeMainMethod (AbstractExecJavaBase.java:402)
    at org.codehaus.mojo.exec.ExecJavaMojo.executeMainMethod (ExecJavaMojo.java:142)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.doExecClassLoader (AbstractExecJavaBase.java:377)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.lambda$execute$0 (AbstractExecJavaBase.java:287)
    at java.lang.Thread.run (Thread.java:1474)
JDK 25

See Also