Return | Method | Summary |
---|---|---|
static<T> Collection<T> | unmodifiableCollection(Collection<? extends T> c) | Returns an unmodifiable view of the specified collection. |
static<T> List<T> | unmodifiableList(List<? extends T> list) | Returns an unmodifiable view of the specified list. |
static<K,V> Map<K,V> | unmodifiableMap(Map<? extends K,? extends V> m) | Returns an unmodifiable view of the specified map. |
static<T> Set<T> | unmodifiableSet(Set<? extends T> s) | Returns an unmodifiable view of the specified set. |
static<K,V> SortedMap<K,V> | unmodifiableSortedMap(SortedMap<K,? extends V> m) | Returns an unmodifiable view of the specified sorted map. |
static<T> SortedSet<T> | unmodifiableSortedSet(SortedSet<T> s) | Returns an unmodifiable view of the specified sorted set. |
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
public class Main {
public static void main(String args[]) {
List<Character> list = new ArrayList<Character>();
list.add('X');
System.out.println("Element added to list: " + list.get(0));
Collection<Character> immutableCol = Collections.unmodifiableCollection(list);
immutableCol.add('Y');
}
}
The output:
Element added to list: X
Exception in thread "main" java.lang.UnsupportedOperationException
at java.util.Collections$UnmodifiableCollection.add(Collections.java:1018)
at Main.main(Main.java:17)
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class Main {
public static void main(String args[]) throws Exception {
List<String> list = new ArrayList<String>();
list.add("A");
list.add("B");
list.add("C");
list = Collections.unmodifiableList(list);
list.add(1, "G");
System.out.println(list);
}
}
The output:
Exception in thread "main" java.lang.UnsupportedOperationException
at java.util.Collections$UnmodifiableList.add(Collections.java:1159)
at Main.main(Main.java:13)
import java.util.Collections;
import java.util.Hashtable;
import java.util.Map;
public class Main {
public static void main(String[] s) {
Hashtable<String,String> table = new Hashtable<String,String>();
table.put("key1", "value1");
table.put("key2", "value2");
table.put("key3", "value3");
Map m = Collections.unmodifiableMap(table);
m.put("key3", "value3");
System.out.println(m);
}
}
The output:
Exception in thread "main" java.lang.UnsupportedOperationException
at java.util.Collections$UnmodifiableMap.put(Collections.java:1285)
at Main.main(Main.java:14)
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
public class Main {
public static void main(String[] args) {
Set OBJECT_SET;
Set objectSet = new HashSet();
objectSet.add(new Integer(5));
objectSet.add(null);
OBJECT_SET = Collections.unmodifiableSet(objectSet);
final Iterator iter = OBJECT_SET.iterator();
Object obj = null;
while (iter.hasNext()) {
obj = iter.next();
if (obj instanceof Number) {
System.out.println(obj);
}
}
}
}
The output:
5
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