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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.util.internal;
  
  import static io.netty.util.internal.ObjectUtil.checkNonEmpty;
  
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.security.AccessController;
  import java.security.PrivilegedAction;
  
  /**
   * A collection of utility methods to retrieve and parse the values of the Java system properties.
   */
  public final class SystemPropertyUtil {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(SystemPropertyUtil.class);
  
      /**
       * Returns {@code true} if and only if the system property with the specified {@code key}
       * exists.
       */
      public static boolean contains(String key) {
          return get(key) != null;
      }
  
      /**
       * Returns the value of the Java system property with the specified
       * {@code key}, while falling back to {@code null} if the property access fails.
       *
       * @return the property value or {@code null}
       */
      public static String get(String key) {
          return get(key, 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(final String key, String def) {
          checkNonEmpty(key, "key");
  
          String value = null;
          try {
              if (System.getSecurityManager() == null) {
                  value = System.getProperty(key);
              } else {
                  value = AccessController.doPrivileged(new PrivilegedAction<String>() {
                      @Override
                      public String run() {
                          return System.getProperty(key);
                      }
                  });
              }
          } catch (SecurityException e) {
              logger.warn("Unable to retrieve a system property '{}'; default values will be used.", key, e);
          }
  
          if (value == null) {
              return 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 boolean getBoolean(String key, boolean def) {
          String value = get(key);
          if (value == null) {
              return def;
          }
 
         value = value.trim().toLowerCase();
         if (value.isEmpty()) {
             return def;
         }
 
         if ("true".equals(value) || "yes".equals(value) || "1".equals(value)) {
             return true;
         }
 
         if ("false".equals(value) || "no".equals(value) || "0".equals(value)) {
             return false;
         }
 
         logger.warn(
                 "Unable to parse the boolean system property '{}':{} - using the default value: {}",
                 key, value, def
         );
 
         return def;
     }
 
     /**
      * 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 getInt(String key, int def) {
         String value = get(key);
         if (value == null) {
             return def;
         }
 
         value = value.trim();
         try {
             return Integer.parseInt(value);
         } catch (Exception e) {
             // Ignore
         }
 
         logger.warn(
                 "Unable to parse the integer system property '{}':{} - using the default value: {}",
                 key, value, def
         );
 
         return def;
     }
 
     /**
      * 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 long getLong(String key, long def) {
         String value = get(key);
         if (value == null) {
             return def;
         }
 
         value = value.trim();
         try {
             return Long.parseLong(value);
         } catch (Exception e) {
             // Ignore
         }
 
         logger.warn(
                 "Unable to parse the long integer system property '{}':{} - using the default value: {}",
                 key, value, def
         );
 
         return def;
     }
 
     private SystemPropertyUtil() {
         // Unused
     }
 }