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Groovy: A powerful, dynamic language for the JVM
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/*
 * Copyright 2003-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (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
 * limitations under the License.
 */
package org.codehaus.groovy.util;

import java.lang.ref.PhantomReference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;


public enum ReferenceType {
    SOFT {
        @Override
        protected  Reference createReference(T value, V handler, ReferenceQueue queue) {
            return new SoftRef(value, handler, queue);
        }
    },
    WEAK {
        @Override
        protected  Reference createReference(T value, V handler, ReferenceQueue queue) {
            return new WeakRef(value, handler, queue);
        }
    },
    PHANTOM {
        @Override
        protected  Reference createReference(T value, V handler, ReferenceQueue queue) {
            return new PhantomRef(value, handler, queue);
        }            
    },
    HARD {
        @Override
        protected  Reference createReference(T value, V handler, ReferenceQueue queue) {
            return new HardRef(value, handler, queue);
        }
    };
    protected abstract  Reference createReference(T value, V handler, ReferenceQueue queue);
    
    private static class SoftRef extends SoftReference implements Reference {
        private final V handler;
        public SoftRef(TT referent, V handler, ReferenceQueue q) {
            super(referent, q);
            this.handler = handler;
        }
        public V getHandler() {
            return handler;
        }        
    }
    
    private static class WeakRef extends WeakReference implements Reference {
        private final V handler;
        public WeakRef(TT referent, V handler, ReferenceQueue q) {
            super(referent, q);
            this.handler = handler;
        }
        public V getHandler() {
            return handler;
        }            
    }
    
    private static class PhantomRef extends PhantomReference implements Reference {
        private final V handler;
        public PhantomRef(TT referent, V handler, ReferenceQueue q) {
            super(referent, q);
            this.handler = handler;
        }
        public V getHandler() {
            return handler;
        }            
    }
    
    private static class HardRef implements Reference {
        private TT ref;
        private final V handler;
        public HardRef(TT referent, V handler, ReferenceQueue q) {
            this.ref = referent;
            this.handler = handler;
        }
        public V getHandler() {
            return handler;
        }
        public TT get() {
            return ref;
        }
        public void clear() {
            ref = null;
        }        
    }
    
}