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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2009 Red Hat, Inc.
 *
 * Red Hat licenses this file to you 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.jboss.netty.util.internal;

import java.util.regex.Pattern;

/**
 * Accesses the system property swallowing a {@link SecurityException}.
 *
 * @author The Netty Project
 * @author Trustin Lee
 *
 * @version $Rev: 2161 $, $Date: 2010-02-18 11:12:15 +0900 (Thu, 18 Feb 2010) $
 *
 */
public class SystemPropertyUtil {

    /**
     * Returns the value of the Java system property with the specified
     * {@code key}.
     *
     * @return the property value.
     *         {@code null} if there's no such property or if an access to the
     *         specified property is not allowed.
     */
    public static String get(String key) {
        try {
            return System.getProperty(key);
        } catch (Exception e) {
            return null;
        }
    }

    /**
     * Returns the value of the Java system property with the specified
     * {@code key}, while falling back to the specified default value if
     * the property access fails.
     *
     * @return the property value.
     *         {@code def} if there's no such property or if an access to the
     *         specified property is not allowed.
     */
    public static String get(String key, String def) {
        String value = get(key);
        if (value == null) {
            value = def;
        }
        return value;
    }

    /**
     * Returns the value of the Java system property with the specified
     * {@code key}, while falling back to the specified default value if
     * the property access fails.
     *
     * @return the property value.
     *         {@code def} if there's no such property or if an access to the
     *         specified property is not allowed.
     */
    public static int get(String key, int def) {
        String value = get(key);
        if (value == null) {
            return def;
        }

        if (Pattern.matches("-?[0-9]+", value)) {
            return Integer.parseInt(value);
        } else {
            return def;
        }
    }

    private SystemPropertyUtil() {
        // Unused
    }
}