48 lines
1.5 KiB
Java
48 lines
1.5 KiB
Java
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//: containers/ReadOnly.java
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// Using the Collections.unmodifiable methods.
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import java.util.*;
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import net.mindview.util.*;
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import static net.mindview.util.Print.*;
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public class ReadOnly {
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static Collection<String> data =
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new ArrayList<String>(Countries.names(6));
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public static void main(String[] args) {
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Collection<String> c =
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Collections.unmodifiableCollection(
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new ArrayList<String>(data));
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print(c); // Reading is OK
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//! c.add("one"); // Can't change it
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List<String> a = Collections.unmodifiableList(
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new ArrayList<String>(data));
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ListIterator<String> lit = a.listIterator();
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print(lit.next()); // Reading is OK
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//! lit.add("one"); // Can't change it
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Set<String> s = Collections.unmodifiableSet(
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new HashSet<String>(data));
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print(s); // Reading is OK
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//! s.add("one"); // Can't change it
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// For a SortedSet:
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Set<String> ss = Collections.unmodifiableSortedSet(
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new TreeSet<String>(data));
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Map<String,String> m = Collections.unmodifiableMap(
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new HashMap<String,String>(Countries.capitals(6)));
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print(m); // Reading is OK
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//! m.put("Ralph", "Howdy!");
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// For a SortedMap:
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Map<String,String> sm =
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Collections.unmodifiableSortedMap(
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new TreeMap<String,String>(Countries.capitals(6)));
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}
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} /* Output:
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[ALGERIA, ANGOLA, BENIN, BOTSWANA, BULGARIA, BURKINA FASO]
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ALGERIA
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[BULGARIA, BURKINA FASO, BOTSWANA, BENIN, ANGOLA, ALGERIA]
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{BULGARIA=Sofia, BURKINA FASO=Ouagadougou, BOTSWANA=Gaberone, BENIN=Porto-Novo, ANGOLA=Luanda, ALGERIA=Algiers}
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*///:~
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