Make a Collection Read-Only


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);
  }
}
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Collection Collection:
  1. Fill a collection
  2. Get the difference of two collections
  3. Get the min value within a collection
  4. Is collection empty, and all of its elements are empty
  5. Make a Collection Read-Only
  6. Make a collection an immutable collection
  7. Sort custom class and user defined Comparator