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Java Program to convert a Map to a read only map
Let’s say the following is our Map −
Map<String, String>map = new HashMap<String,String>(); map.put("1","A"); map.put("2","B"); map.put("3","C");
Make it read-only using the unmodifiableMap() method −
map = Collections.unmodifiableMap(map);
Example
import java.util.Collections; import java.util.HashMap; import java.util.Map; public class Demo { public static void main(String[] argv) throws Exception { Map<String, String>map = new HashMap<String,String>(); map.put("1","A"); map.put("2","B"); map.put("3","C"); // making it read-only map = Collections.unmodifiableMap(map); try { map.put("4","D"); map.put("5","E"); map.put("6","F"); } catch (UnsupportedOperationException e) { System.out.println(e.getMessage()); } } }
Output
null
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