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 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
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package org.apache.commons.collections.functors;

import java.io.Serializable;
import java.util.Iterator;
import java.util.Map;

import org.apache.commons.collections.Closure;
import org.apache.commons.collections.Predicate;

Closure implementation calls the closure whose predicate returns true,
like a switch statement.
Author:
Stephen Colebourne
Since:
Commons Collections 3.0
Version:
$Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $/**
 * Closure implementation calls the closure whose predicate returns true,
 * like a switch statement.
 * 
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
 *
 * @author Stephen Colebourne
 */
public class SwitchClosure implements Closure, Serializable {

    
Serial version UID /** Serial version UID */
    private static final long serialVersionUID = 3518477308466486130L;

    
The tests to consider /** The tests to consider */
    private final Predicate[] iPredicates;
    
The matching closures to call /** The matching closures to call */
    private final Closure[] iClosures;
    
The default closure to call if no tests match /** The default closure to call if no tests match */
    private final Closure iDefault;

    
Factory method that performs validation and copies the parameter arrays.
Params:
predicates –  array of predicates, cloned, no nulls
closures –  matching array of closures, cloned, no nulls
defaultClosure –  the closure to use if no match, null means nop
Throws:
IllegalArgumentException – if array is null
IllegalArgumentException – if any element in the array is null
Returns:
the chained closure/**
     * Factory method that performs validation and copies the parameter arrays.
     * 
     * @param predicates  array of predicates, cloned, no nulls
     * @param closures  matching array of closures, cloned, no nulls
     * @param defaultClosure  the closure to use if no match, null means nop
     * @return the <code>chained</code> closure
     * @throws IllegalArgumentException if array is null
     * @throws IllegalArgumentException if any element in the array is null
     */
    public static Closure getInstance(Predicate[] predicates, Closure[] closures, Closure defaultClosure) {
        FunctorUtils.validate(predicates);
        FunctorUtils.validate(closures);
        if (predicates.length != closures.length) {
            throw new IllegalArgumentException("The predicate and closure arrays must be the same size");
        }
        if (predicates.length == 0) {
            return (defaultClosure == null ? NOPClosure.INSTANCE : defaultClosure);
        }
        predicates = FunctorUtils.copy(predicates);
        closures = FunctorUtils.copy(closures);
        return new SwitchClosure(predicates, closures, defaultClosure);
    }

    
Create a new Closure that calls one of the closures depending 
on the predicates. 

The Map consists of Predicate keys and Closure values. A closure 
is called if its matching predicate returns true. Each predicate is evaluated
until one returns true. If no predicates evaluate to true, the default
closure is called. The default closure is set in the map with a 
null key. The ordering is that of the iterator() method on the entryset 
collection of the map.
Params:
predicatesAndClosures –  a map of predicates to closures
Throws:
IllegalArgumentException – if the map is null
IllegalArgumentException – if any closure in the map is null
ClassCastException –  if the map elements are of the wrong type
Returns:
the switch closure/**
     * Create a new Closure that calls one of the closures depending 
     * on the predicates. 
     * <p>
     * The Map consists of Predicate keys and Closure values. A closure 
     * is called if its matching predicate returns true. Each predicate is evaluated
     * until one returns true. If no predicates evaluate to true, the default
     * closure is called. The default closure is set in the map with a 
     * null key. The ordering is that of the iterator() method on the entryset 
     * collection of the map.
     * 
     * @param predicatesAndClosures  a map of predicates to closures
     * @return the <code>switch</code> closure
     * @throws IllegalArgumentException if the map is null
     * @throws IllegalArgumentException if any closure in the map is null
     * @throws ClassCastException  if the map elements are of the wrong type
     */
    public static Closure getInstance(Map predicatesAndClosures) {
        Closure[] closures = null;
        Predicate[] preds = null;
        if (predicatesAndClosures == null) {
            throw new IllegalArgumentException("The predicate and closure map must not be null");
        }
        if (predicatesAndClosures.size() == 0) {
            return NOPClosure.INSTANCE;
        }
        // convert to array like this to guarantee iterator() ordering
        Closure defaultClosure = (Closure) predicatesAndClosures.remove(null);
        int size = predicatesAndClosures.size();
        if (size == 0) {
            return (defaultClosure == null ? NOPClosure.INSTANCE : defaultClosure);
        }
        closures = new Closure[size];
        preds = new Predicate[size];
        int i = 0;
        for (Iterator it = predicatesAndClosures.entrySet().iterator(); it.hasNext();) {
            Map.Entry entry = (Map.Entry) it.next();
            preds[i] = (Predicate) entry.getKey();
            closures[i] = (Closure) entry.getValue();
            i++;
        }
        return new SwitchClosure(preds, closures, defaultClosure);
    }
    
    
Constructor that performs no validation.
Use getInstance if you want that.
Params:
predicates –  array of predicates, not cloned, no nulls
closures –  matching array of closures, not cloned, no nulls
defaultClosure –  the closure to use if no match, null means nop/**
     * Constructor that performs no validation.
     * Use <code>getInstance</code> if you want that.
     * 
     * @param predicates  array of predicates, not cloned, no nulls
     * @param closures  matching array of closures, not cloned, no nulls
     * @param defaultClosure  the closure to use if no match, null means nop
     */
    public SwitchClosure(Predicate[] predicates, Closure[] closures, Closure defaultClosure) {
        super();
        iPredicates = predicates;
        iClosures = closures;
        iDefault = (defaultClosure == null ? NOPClosure.INSTANCE : defaultClosure);
    }

    
Executes the closure whose matching predicate returns true
Params:
input –  the input object/**
     * Executes the closure whose matching predicate returns true
     * 
     * @param input  the input object
     */
    public void execute(Object input) {
        for (int i = 0; i < iPredicates.length; i++) {
            if (iPredicates[i].evaluate(input) == true) {
                iClosures[i].execute(input);
                return;
            }
        }
        iDefault.execute(input);
    }

    
Gets the predicates, do not modify the array.
Returns:
the predicates
Since:
Commons Collections 3.1/**
     * Gets the predicates, do not modify the array.
     * 
     * @return the predicates
     * @since Commons Collections 3.1
     */
    public Predicate[] getPredicates() {
        return iPredicates;
    }

    
Gets the closures, do not modify the array.
Returns:
the closures
Since:
Commons Collections 3.1/**
     * Gets the closures, do not modify the array.
     * 
     * @return the closures
     * @since Commons Collections 3.1
     */
    public Closure[] getClosures() {
        return iClosures;
    }

    
Gets the default closure.
Returns:
the default closure
Since:
Commons Collections 3.1/**
     * Gets the default closure.
     * 
     * @return the default closure
     * @since Commons Collections 3.1
     */
    public Closure getDefaultClosure() {
        return iDefault;
    }
    
}