--- /dev/null 2015-09-16 15:21:13.000000000 -0700 +++ new/src/java.base/share/classes/jdk.internal.jvmci.options/src/jdk/internal/jvmci/options/StableOptionValue.java 2015-09-16 15:21:13.000000000 -0700 @@ -0,0 +1,75 @@ +/* + * Copyright (c) 2013, 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. + * + * 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 + * or visit www.oracle.com if you need additional information or have any + * questions. + */ +package jdk.internal.jvmci.options; + +/** + * An option that always returns the same {@linkplain #getValue() value}. + */ +public class StableOptionValue extends OptionValue { + + /** + * Creates a stable option value. + */ + public StableOptionValue(T value) { + super(value); + } + + /** + * Used to assert the invariant for stability. Without using locks, this check is not safe + * against races and so it's only an assertion. + */ + private boolean getValueCalled; + + /** + * Creates an uninitialized stable option value for a subclass that initializes itself + * {@link #defaultValue() lazily}. + */ + public StableOptionValue() { + } + + /** + * Gets the value of this option. + */ + @Override + public final T getValue() { + T result = super.getValue(); + assert initGetValueCalled(); + return result; + } + + private boolean initGetValueCalled() { + getValueCalled = true; + return true; + } + + /** + * {@inheritDoc} + *

+ * This must only be called if {@link #getValue()} has never been called. + */ + @Override + public final void setValue(Object v) { + assert !getValueCalled; + super.setValue(v); + } +}