Java示例只读集合

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 {

      List stuff = Arrays.asList(new String[] { "a", "b" });

      List list = new ArrayList(stuff);

      list = Collections.unmodifiableList(list);

      try {

         list.set(0, "new value");

      } catch (UnsupportedOperationException e) {

      }

      Set set = new HashSet(stuff);

      set = Collections.unmodifiableSet(set);

      Map map = new HashMap();

      map = Collections.unmodifiableMap(map);

      System.out.println("Collection is read-only now.");

   }

}