SystemUtils.java

/**
 * Copyright 2005-2014 Restlet
 * 
 * The contents of this file are subject to the terms of one of the following
 * open source licenses: Apache 2.0 or or EPL 1.0 (the "Licenses"). You can
 * select the license that you prefer but you may not use this file except in
 * compliance with one of these Licenses.
 * 
 * You can obtain a copy of the Apache 2.0 license at
 * http://www.opensource.org/licenses/apache-2.0
 * 
 * You can obtain a copy of the EPL 1.0 license at
 * http://www.opensource.org/licenses/eclipse-1.0
 * 
 * See the Licenses for the specific language governing permissions and
 * limitations under the Licenses.
 * 
 * Alternatively, you can obtain a royalty free commercial license with less
 * limitations, transferable or non-transferable, directly at
 * http://restlet.com/products/restlet-framework
 * 
 * Restlet is a registered trademark of Restlet S.A.S.
 */

package org.restlet.engine.util;

/**
 * System utilities.
 * 
 * @author Jerome Louvel
 */
public class SystemUtils {

    /**
     * Indicates if both fields are equal. For this to be true, they must either
     * be both null or return true to the {@link Object#equals(Object)} method.
     * 
     * @param source
     *            The source field.
     * @param target
     *            The target field.
     * @return True if both fields are equals.
     */
    public static boolean equals(Object source, Object target) {
        return (target == source) || (target != null && target.equals(source));
    }

    // [ifndef gwt] method
    /**
     * Parses the "java.version" system property and returns the first digit of
     * the version number of the Java Runtime Environment (e.g. "1" for
     * "1.3.0").
     * 
     * @see <a href="http://java.sun.com/j2se/versioning_naming.html">Official
     *      Java versioning</a>
     * @return The major version number of the Java Runtime Environment.
     */
    public static int getJavaMajorVersion() {
        int result;
        final String javaVersion = System.getProperty("java.version");
        try {
            result = Integer.parseInt(javaVersion.substring(0,
                    javaVersion.indexOf(".")));
        } catch (Exception e) {
            result = 0;
        }

        return result;
    }

    // [ifndef gwt] method
    /**
     * Parses the "java.version" system property and returns the second digit of
     * the version number of the Java Runtime Environment (e.g. "3" for
     * "1.3.0").
     * 
     * @see <a href="http://java.sun.com/j2se/versioning_naming.html">Official
     *      Java versioning</a>
     * @return The minor version number of the Java Runtime Environment.
     */
    public static int getJavaMinorVersion() {
        int result;
        final String javaVersion = System.getProperty("java.version");
        try {
            result = Integer.parseInt(javaVersion.split("\\.")[1]);
        } catch (Exception e) {
            result = 0;
        }

        return result;
    }

    // [ifndef gwt] method
    /**
     * Parses the "java.version" system property and returns the update release
     * number of the Java Runtime Environment (e.g. "10" for "1.3.0_10").
     * 
     * @see <a href="http://java.sun.com/j2se/versioning_naming.html">Official
     *      Java versioning</a>
     * @return The release number of the Java Runtime Environment or 0 if it
     *         does not exist.
     */
    public static int getJavaUpdateVersion() {
        int result;
        final String javaVersion = System.getProperty("java.version");
        try {
            result = Integer.parseInt(javaVersion.substring(javaVersion
                    .indexOf('_') + 1));
        } catch (Exception e) {
            result = 0;
        }

        return result;
    }

    /**
     * Computes the hash code of a set of objects. Follows the algorithm
     * specified in List.hasCode().
     * 
     * @param objects
     *            the objects to compute the hashCode
     * 
     * @return The hash code of a set of objects.
     */
    public static int hashCode(Object... objects) {
        int result = 17;

        if (objects != null) {
            for (final Object obj : objects) {
                result = 31 * result + (obj == null ? 0 : obj.hashCode());
            }
        }

        return result;
    }

    // [ifndef gwt] method
    /**
     * Indicates if the current operating system is in the Windows family.
     * 
     * @return True if the current operating system is in the Windows family.
     */
    public static boolean isWindows() {
        return System.getProperty("os.name").toLowerCase().indexOf("win") >= 0;
    }

    /**
     * Private constructor to ensure that the class acts as a true utility class
     * i.e. it isn't instantiable and extensible.
     */
    private SystemUtils() {
    }

}