src/java.base/share/classes/jdk/internal/misc/PreviewFeatures.java

/*
 * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */
package jdk.internal.misc;

/**
 * Defines static methods to test if preview features are enabled at run-time.
 */
public class PreviewFeatures {
    private static final boolean ENABLED = isPreviewEnabled();

    private PreviewFeatures() {
    }

    /**
     * {@return true if preview features are enabled, otherwise false}
     */
    public static boolean isEnabled() {
        return ENABLED;
    }

    /**
     * Ensures that preview features are enabled.
     * @throws UnsupportedOperationException if preview features are not enabled
     */
    public static void ensureEnabled() {
        if (!isEnabled()) {
            throw new UnsupportedOperationException(
                "Preview Features not enabled, need to run with --enable-preview");
        }
    }

    private static native boolean isPreviewEnabled();
}