Class EmptyMap

src/main/java/freemarker/template/EmptyMap.java:15–70

Read-only empty map. #remove(Object), #clear() and #putAll(Map) with an empty Map as parameter are supported operations (and do nothing) since FreeMarker 2.3.20. @deprecated Use Collections#EMPTY_MAP on J2SE 1.3 or later.

 * @deprecated Use {@link Collections#EMPTY_MAP} on J2SE 1.3 or later.   
 */
public class EmptyMap implements Map, Cloneable {
    public static final EmptyMap instance = new EmptyMap(); 
    
    public void clear() {
        // no op
    }
    
    public boolean containsKey(Object arg0) {
        return false;
    }
    
    public boolean containsValue(Object arg0) {
        return false;
    }
    
    public Set entrySet() {
        return Collections.EMPTY_SET;
    }
    
    public Object get(Object arg0) {
        return null;
    }
    
    public boolean isEmpty() {
        return true;
    }
    
    public Set keySet() {
        return Collections.EMPTY_SET;
    }
    
    public Object put(Object arg0, Object arg1) {
        throw new UnsupportedOperationException("This Map is read-only.");
    }
    
    public void putAll(Map arg0) {
        // Checking for arg0.isEmpty() wouldn't reflect precisely how putAll in
        // AbstractMap works. 
        if (arg0.entrySet().iterator().hasNext()) {
            throw new UnsupportedOperationException("This Map is read-only.");
        }
    }
    
    public Object remove(Object arg0) {
        return null;
    }
    
    public int size() {
        return 0;
    }
    
    public Collection values() {
        return Collections.EMPTY_LIST;
    }

}