Java Collections synchronizedMap() Method with Examples

by Online Tutorials Library July 22, 2022

Java Collections synchronizedMap() Method

The synchronizedMap() method of Java Collections class is used to get a synchronized (thread-safe) map backed by the specified map.

Syntax

Following is the declaration of synchronizedMap() method:

Parameter

Parameter	Description	Required/Optional
m	It is the map which will be wrapped in a synchronized map.	Required

Returns

The synchronizedMap() method returns a synchronized view of the specified Map.

Exceptions

Example 1

  import java.util.*;  public class CollectionsSynchronizedMapExample1 {  public static void main(String[] args) {  Map map = new HashMap();  map.put(“1”, “Rahul”);  map.put(“4”, “Karan”);  map.put(“3”, “Mohan”);  Map synmap = Collections.synchronizedMap(map);  System.out.println(“Synchronized map is :” + synmap);                    }  }  ,>,>,>

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Output:

Synchronized map is :{1=Rahul, 3=Mohan, 4=Karan}

Example 2

  import java.util.*;  public class CollectionsSynchronizedMapExample2 {  public static void main(String[] args) {  Map map = new HashMap<>();  map.put(1, 1001);  map.put(2, 1002);  map.put(3, 1003);  map.put(4, 1004);  map.put(5, 1005);  System.out.println(“Map before Synchronized map: ” + map);  Map synmap = Collections.synchronizedMap(map);        map.remove(4, 1004);       System.out.println(“Synchronized map after remove(4, 1004):” + synmap);       }  }  ,>,>

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Output:

Map before Synchronized map: {1=1001, 2=1002, 3=1003, 4=1004, 5=1005}  Synchronized map after remove(4, 1004):{1=1001, 2=1002, 3=1003, 5=1005}

Example 3

  import java.util.*;  import java.util.concurrent.ExecutorService;  import java.util.concurrent.Executors;  import java.util.concurrent.TimeUnit;  import java.util.concurrent.atomic.AtomicInteger;  public class CollectionsSynchronizedMapExample3 {  private static AtomicInteger counter = new AtomicInteger();  public static void main(String[] args) throws  InterruptedException{       Map m = new HashMap<>();       Map map = Collections.synchronizedMap(m);       final ExecutorService e = Executors.newFixedThreadPool(10);       for (int i = 0; i < 10000; 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 10000       }  }  ,>,>

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Output:

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Java Collections synchronizedMap() Method with Examples

Java Collections synchronizedMap() Method

Syntax

Parameter

Returns

Exceptions

Example 1

Example 2

Example 3

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