Java Collection How to - Convert a Map to a read only map

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Question

We would like to know how to convert a Map to a read only map.

Answer

//from w  ww .  java 2 s. c  o m
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class Main {
  public static void main(String[] argv) throws Exception {

    Map map = new HashMap();
    map = Collections.unmodifiableMap(map);


    try {
      map.put("key","new value");
    } catch (UnsupportedOperationException e) {
      System.out.println(e.getMessage());
    }

  }
}

The code above generates the following result.

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