zkoss/zk

/* Generics.java

    Purpose:
        
    Description:
        
    History:
        Tue Sep 14 18:03:59 TST 2010, Created by tomyeh

Copyright (C) 2010 Potix Corporation. All Rights Reserved.

*/
package org.zkoss.lang;

import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.Set;

/**
 * Utilities to handle generic types, such as converting a non-type object
 * to a generic type without warning.
 *
 * @author tomyeh
 * @since 6.0.0
 */
public class Generics {
    /** Returns a type-safe generic class of the given type-less class.
     */
    @SuppressWarnings("unchecked")
    public static final <T> Class<T> cast(Class cls) {
        return (Class<T>)cls;
    }
    /** Force to cast an object to the given type.
     * Notice that it is not safe to use, unless you are sure that <code>o</code>
     * is an instance of T.
     */
    @SuppressWarnings("unchecked")
    public static final <T> T cast(Object o) {
        return (T)o;
    }
    /** Returns a type-safe generic iterator of the given un-typed iterator.
     */
    @SuppressWarnings("unchecked")
    public static final <T> Iterator<T> cast(Iterator it) {
        return it;
    }
    /** Returns a type-safe generic list iterator of the given un-typed list iterator.
     */
    @SuppressWarnings("unchecked")
    public static final <T> ListIterator<T> cast(ListIterator it) {
        return it;
    }
    /** Returns a type-safe generic enumeration of the given un-typed enumeration.
     */
    @SuppressWarnings("unchecked")
    public static final <T> Enumeration<T> cast(Enumeration en) {
        return en;
    }

    /** Returns a type-safe generic collection of the given un-typed collection.
     */
    @SuppressWarnings("unchecked")
    public static final <T> Collection<T> cast(Collection col) {
        return col;
    }
    /** Returns a type-safe generic list of the given un-typed list.
     */
    @SuppressWarnings("unchecked")
    public static final <T> List<T> cast(List list) {
        return list;
    }
    /** Returns a type-safe generic set of the given un-typed set.
     */
    @SuppressWarnings("unchecked")
    public static final <T> Set<T> cast(Set set) {
        return set;
    }
    /** Returns a type-safe generic map of the given un-typed map.
     */
    @SuppressWarnings("unchecked")
    public static final <K, V> Map<K, V> cast(Map map) {
        return map;
    }
    /** Returns a type-safe generic thread-local of the given un-typed thread-local.
     */
    @SuppressWarnings("unchecked")
    public static final <T> ThreadLocal<T> cast(ThreadLocal tl) {
        return tl;
    }
}