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Java Utilities
There is a newer version: 2.18.0
package com.cedarsoftware.util;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
import java.util.function.Supplier;

/**
 * SealableMap provides a Map or Map wrapper that can be 'sealed' and 'unsealed.'  When sealed, the
 * Map is mutable, when unsealed it is immutable (read-only). The view methods iterator(), keySet(),
 * values(), and entrySet() return a view that honors the Supplier's sealed state.  The sealed state
 * can be changed as often as needed.
 * 


 * NOTE: Please do not reformat this code as the current format makes it easy to see the overall structure.
 * 


 * @author John DeRegnaucourt ([email protected])
 *         

 *         Copyright (c) Cedar Software LLC
 *         


 *         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
 *         


 *         License
 *         


 *         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.
 */
public class SealableMap implements Map {
    private final Map map;
    private final transient Supplier sealedSupplier;

    /**
     * Create a SealableMap. Since a Map is not supplied, this will use a ConcurrentHashMapNullSafe internally. If you
     * want a HashMap to be used internally, use the SealableMap constructor that takes a Map and pass it the
     * instance you want it to wrap.
     * @param sealedSupplier {@code Supplier} that returns 'true' to indicate sealed, 'false' for mutable.
     */
    public SealableMap(Supplier sealedSupplier) {
        this.sealedSupplier = sealedSupplier;
        this.map = new ConcurrentHashMapNullSafe<>();
    }

    /**
     * Use this constructor to wrap a Map (any kind of Map) and make it a SealableMap. No duplicate of the Map is
     * created and the original map is operated on directly if unsealed, or protected from changes if sealed.
     * @param map Map instance to protect.
     * @param sealedSupplier {@code Supplier} that returns 'true' to indicate sealed, 'false' for mutable.
     */
    public SealableMap(Map map, Supplier sealedSupplier) {
        this.sealedSupplier = sealedSupplier;
        this.map = map;
    }
    
    private void throwIfSealed() {
        if (sealedSupplier.get()) {
            throw new UnsupportedOperationException("This map has been sealed and is now immutable");
        }
    }

    // Immutable
    public boolean equals(Object obj) { return map.equals(obj); }
    public int hashCode() { return map.hashCode(); }
    public String toString() { return map.toString(); }
    public int size() { return map.size(); }
    public boolean isEmpty() { return map.isEmpty(); }
    public boolean containsKey(Object key) { return map.containsKey(key); }
    public boolean containsValue(Object value) { return map.containsValue(value); }
    public V get(Object key) { return map.get(key); }
    public Set keySet() { return new SealableSet<>(map.keySet(), sealedSupplier); }
    public Collection values() { return new SealableList<>(new ArrayList<>(map.values()), sealedSupplier); }
    public Set> entrySet() { return new SealableSet<>(map.entrySet(), sealedSupplier); }

    // Mutable
    public V put(K key, V value) { throwIfSealed(); return map.put(key, value); }
    public V remove(Object key) { throwIfSealed(); return map.remove(key); }
    public void putAll(Map m) { throwIfSealed(); map.putAll(m); }
    public void clear() { throwIfSealed(); map.clear(); }
}