1 /* 2 * Copyright (c) 2016, 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 org.graalvm.compiler.phases.common; 24 25 import java.util.function.Supplier; 26 27 /** 28 * A {@link Supplier} which always returns the same value, computed from an other supplier on the 29 * first access. 30 * 31 * <p> 32 * This implementation is not thread-safe and assumes the underlying supplier does not return null. 33 * If the underlying supplier returns null it will be called on each access until it returns a 34 * non-null value. 35 * </p> 36 */ 37 public class LazyValue<T> implements Supplier<T> { 38 private final Supplier<T> supplier; 39 private T value; 40 41 public LazyValue(Supplier<T> supplier) { 42 this.supplier = supplier; 43 } 44 45 @Override 46 public T get() { 47 if (value == null) { 48 value = supplier.get(); 49 } 50 return value; 51 } 52 }