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Java Collections - Collections.synchronizedNavigableMap() Examples

[Last Updated: Nov 8, 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 <K,V> NavigableMap<K,V> synchronizedNavigableMap(NavigableMap<K,V> m)

Returns a synchronized (thread-safe) NavigableMap backed by the specified NavigableMap.


Examples


package com.logicbig.example.collections;

import java.util.NavigableMap;
import java.util.Random;
import java.util.TreeMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

public class SynchronizedNavigableMapExample {

    private static AtomicInteger counter = new AtomicInteger();

    public static void main(String... args) throws InterruptedException {
        NavigableMap<Integer, Integer> map = new TreeMap<>();

        final ExecutorService e = Executors.newFixedThreadPool(10);
        for (int i = 0; i < 10; i++) {
            e.execute(() -> map.put(counter.incrementAndGet(),
                    (int) (Math.random() * 100)));
        }
        e.shutdown();
        e.awaitTermination(1000, TimeUnit.SECONDS);
        System.out.println(map.size());//should be 10
    }
}

Output

8




Using Collections.synchronizedNavigableMap: 

package com.logicbig.example.collections;

import java.util.Collections;
import java.util.NavigableMap;
import java.util.TreeMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

public class SynchronizedNavigableMapExample2 {
    private static AtomicInteger counter = new AtomicInteger();

    public static void main(String... args) throws InterruptedException {
        NavigableMap<Integer, Integer> m = new TreeMap<>();
        NavigableMap<Integer, Integer> map = Collections.synchronizedNavigableMap(m);

        final ExecutorService e = Executors.newFixedThreadPool(10);
        for (int i = 0; i < 10; i++) {
            e.execute(() -> map.put(counter.incrementAndGet(),
                    (int) (Math.random() * 100)));
        }
        e.shutdown();
        e.awaitTermination(1000, TimeUnit.SECONDS);
        System.out.println(map.size());//should be 10
    }
}

Output

10

See Also