org.openscada.utils.interner.InternerHelper.java Source code

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Here is the source code for org.openscada.utils.interner.InternerHelper.java

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/*
 * This file is part of the openSCADA project
 * Copyright (C) 2011-2012 TH4 SYSTEMS GmbH (http://th4-systems.com)
 *
 * openSCADA is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 3
 * only, as published by the Free Software Foundation.
 *
 * openSCADA is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License version 3 for more details
 * (a copy is included in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU Lesser General Public License
 * version 3 along with openSCADA. If not, see
 * <http://opensource.org/licenses/lgpl-3.0.html> for a copy of the LGPLv3 License.
 */

package org.openscada.utils.interner;

import com.google.common.collect.Interner;
import com.google.common.collect.Interners;

public final class InternerHelper {
    private InternerHelper() {
    }

    private static class NullSafeInterner implements Interner<String> {
        private final Interner<String> interner;

        private NullSafeInterner(final Interner<String> interner) {
            this.interner = interner;
        }

        @Override
        public String intern(final String string) {
            if (string == null) {
                return null;
            }
            return this.interner.intern(string);
        };
    }

    public static Interner<String> makeInterner(final String specificPropertyName, final String defaultType) {
        final String type = System.getProperty(specificPropertyName,
                System.getProperty("org.openscada.defaultStringInterner", defaultType));
        if ("weak".equals(type)) {
            return new NullSafeInterner(Interners.<String>newWeakInterner());
        } else if ("strong".equals(type)) {
            return new NullSafeInterner(Interners.<String>newStrongInterner());
        } else if ("java".equals(type)) {
            return new JavaStringInterner();
        } else {
            return makeNoOpInterner();
        }
    }

    public static Interner<String> makeNoOpInterner() {
        return new Interner<String>() {

            @Override
            public String intern(final String string) {
                return string;
            }
        };
    }
}