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Java Simplified. Extensions and Useful Constructs for the Java Platform. Codeprimate Elements (a.k.a. cp-elements) is a Java library and micro-framework used to simplify the development of software applications written in Java. Elements packages several APIs into one library in order to address various application concerns and aspects of software design and development collectively and conveniently. Elements is a highly simple, yet robust and proven library built on solid OO principles, software design patterns and best practices to effectively solve common and reoccurring problems in software development.
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/*
 * Copyright 2016 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.cp.elements.lang;

/**
 * SystemUtils is an abstract utility class designed to interact with and access properties of the Java System class.
 *
 * @author John J. Blum
 * @see java.lang.System
 * @since 1.0.0
 */
@SuppressWarnings("unused")
public abstract class SystemUtils {

  // Present Working Directory (PWD)
  public static final String CURRENT_DIRECTORY = System.getProperty("user.dir");

  // Java Virtual Machine (JVM) Names
  public static final String IBM_J9_JVM_NAME = "J9";
  public static final String ORACLE_HOTSPOT_JVM_NAME = "HotSpot";
  public static final String ORACLE_JROCKIT_JVM_NAME = "JRockit";

  // Java Virtual Machine (JVM) Vendor Names
  public static final String APPLE_JVM_VENDOR = "Apple";
  public static final String IBM_JVM_VENDOR = "IBM";
  public static final String ORACLE_JVM_VENDOR = "Oracle";

  // Operating System Names
  public static final String LINUX_OS_NAME = "Linux";
  public static final String MAC_OSX_NAME = "Mac";
  public static final String WINDOWS_OS_NAME = "Windows";

  /**
   * Utility method to determine if the installed Java Runtime Environment (JRE) meets the minimum expected version.
   * Java versions are typically of the form "1.8.0_66".  The Java version is determined by the "java.version"
   * System property.
   *
   * @param expectedVersion a numerical String value specifying the expected minimum version
   * of the installed Java Runtime Environment.
   * @return a boolean value indicating if the Java Runtime Environment meets the expected minimum version requirement.
   * @see java.lang.System#getProperty(String)
   */
  public static boolean isJavaVersionAtLeast(final String expectedVersion) {
    String actualVersionDigits = StringUtils.getDigits(System.getProperty("java.version"));

    String expectedVersionDigits = StringUtils.pad(StringUtils.getDigits(expectedVersion), '0',
      actualVersionDigits.length());

    try {
      return (Long.parseLong(actualVersionDigits) >= Long.parseLong(expectedVersionDigits));
    }
    catch (NumberFormatException ignore) {
      return false;
    }
  }

  /**
   * Utility method to determine if this Java application process is executing on the Apple JVM.
   *
   * @return a boolean value indicating whether the Java application process is executing and running
   * on the Apple JVM.
   * @see #isJvmMake(String)
   * @see #APPLE_JVM_VENDOR
   */
  public static boolean isAppleJvm() {
    return isJvmMake(APPLE_JVM_VENDOR);
  }

  /**
   * Utility method to determine if this Java application process is executing on the IBM JVM.
   *
   * @return a boolean value indicating whether the Java application process is executing and running
   * on the IBM JVM.
   * @see #isJvmMake(String)
   * @see #IBM_JVM_VENDOR
   */
  public static boolean isIBMJvm() {
    return isJvmMake(IBM_JVM_VENDOR);
  }

  /**
   * Utility method to determine if this Java application process is executing on the Oracle JVM.
   *
   * @return a boolean value indicating whether the Java application process is executing and running
   * on the Oracle JVM.
   * @see #isJvmMake(String)
   * @see #ORACLE_JVM_VENDOR
   */
  public static boolean isOracleJvm() {
    return isJvmMake(ORACLE_JVM_VENDOR);
  }

  /**
   * Determines whether this Java Virtual Machine (JVM) is the expected make (vendor).  The current JVM is determined
   * by the "java.vm.vendor" System property.
   *
   * @param expectedJvmVendor a String indicating the expected JVM vendor (make).
   * @return a boolean value indicating whether this JVM is the expected make.
   * @see java.lang.System#getProperty(String)
   */
  protected static boolean isJvmMake(final String expectedJvmVendor) {
    String jvmVendor = System.getProperty("java.vm.vendor");
    return (jvmVendor != null && jvmVendor.contains(expectedJvmVendor));
  }

  /**
   * Utility method to determine if this Java application process is executing on either the 'client' or 'server'
   * Java HotSpot VM.
   *
   * @return a boolean value indicating whether this Java application process is executing on the Java HotSpot VM.
   * @see #isJvmModel(String)
   * @see #ORACLE_HOTSPOT_JVM_NAME
   */
  public static boolean isHotSpotJvm() {
    return isJvmModel(ORACLE_HOTSPOT_JVM_NAME);
  }

  /**
   * Utility method to determine if this Java application process is executing on the IBM J9 VM.
   *
   * @return a boolean value indicating whether this Java application process is executing on the IBM J9 VM.
   * @see #isJvmModel(String)
   * @see #IBM_J9_JVM_NAME
   */
  public static boolean isJ9Jvm() {
    return isJvmModel(IBM_J9_JVM_NAME);
  }

  /**
   * Utility method to determine if this Java application process is executing on the 'client' or 'server'
   * Oracle JRockit VM.
   *
   * @return a boolean value indicating whether this Java application process is executing on the Oracle JRockit VM.
   * @see #isJvmModel(String)
   * @see #ORACLE_JROCKIT_JVM_NAME
   */
  public static boolean isJRockitJvm() {
    return isJvmModel(ORACLE_JROCKIT_JVM_NAME);
  }

  /**
   * Determines whether this Java Virtual Machine (JVM) is the expected model.  The current JVM is determined
   * by the "java.vm.name" System property.
   *
   * @param expectedJvmName a String indicating the name of the expected JVM model.
   * @return a boolean determining whether this JVM is the expected model.
   * @see java.lang.System#getProperty(String)
   */
  protected static boolean isJvmModel(final String expectedJvmName) {
    String jvmName = System.getProperty("java.vm.name");
    return (jvmName != null && jvmName.contains(expectedJvmName));
  }

  /**
   * Utility method to determine if this Java application process is executing in a Linux operating system environment.
   *
   * @return a boolean value indicating whether this Java application process is executing in Linux.
   * @see #isOS(String)
   * @see #LINUX_OS_NAME
   */
  public static boolean isLinux() {
    return isOS(LINUX_OS_NAME);
  }

  /**
   * Utility method to determine if this Java application process is executing in a Apple Mac OSX operating system
   * environment.
   *
   * @return a boolean value indicating whether this Java application process is executing in Mac OSX.
   * @see #isOS(String)
   * @see #MAC_OSX_NAME
   */
  public static boolean isMacOSX() {
    return isOS(MAC_OSX_NAME);
  }

  /**
   * Utility method to determine if this Java application process is executing in a Microsoft Windows-based
   * operating system environment.
   *
   * @return a boolean value indicating whether this Java application process is executing in Windows.
   * @see #isOS(String)
   * @see #WINDOWS_OS_NAME
   */
  public static boolean isWindows() {
    return isOS(WINDOWS_OS_NAME);
  }

  /**
   * Determines wheehr this Operating System is the expected Operating System environment.  The current OS is determined
   * by the "os.name" System property.
   *
   * @param expectedOsName a String indicating the name of the expected OS environment.
   * @return a boolean value indicating whether this OS is the expected OS.
   * @see java.lang.System#getProperty(String)
   */
  protected static boolean isOS(final String expectedOsName) {
    String osName = System.getProperty("os.name");
    return (osName != null && osName.contains(expectedOsName));
  }

}