1 /* 2 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 package jdk.vm.ci.options; 24 25 /** 26 * An option that always returns the same {@linkplain #getValue() value}. 27 */ 28 public class StableOptionValue<T> extends OptionValue<T> { 29 30 /** 31 * Creates a stable option value. 32 */ 33 public StableOptionValue(T value) { 34 super(value); 35 } 36 37 /** 38 * Used to assert the invariant for stability. Without using locks, this check is not safe 39 * against races and so it's only an assertion. 40 */ 41 private boolean getValueCalled; 42 43 /** 44 * Creates an uninitialized stable option value for a subclass that initializes itself 45 * {@link #defaultValue() lazily}. 46 */ 47 public StableOptionValue() { 48 } 49 50 /** 51 * Gets the value of this option. 52 */ 53 @Override 54 public final T getValue() { 55 T result = super.getValue(); 56 assert initGetValueCalled(); 57 return result; 58 } 59 60 private boolean initGetValueCalled() { 61 getValueCalled = true; 62 return true; 63 } 64 65 /** 66 * {@inheritDoc} 67 * <p> 68 * This must only be called if {@link #getValue()} has never been called. 69 */ 70 @Override 71 public final void setValue(Object v) { 72 assert !getValueCalled; 73 super.setValue(v); 74 } 75 }