platform/util/src/com/intellij/openapi/util/LazyInitializer.java

   1 /*
   2  * Copyright 2000-2009 JetBrains s.r.o.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 package com.intellij.openapi.util;
  17
  18 public abstract class LazyInitializer<Value, Exc extends Throwable> implements ThrowableComputable<Value, Exc> {
  19   private Value myValue;
  20
  21   public Value compute() throws Exc {
  22     if (myValue == null) {
  23       myValue = compute();
  24     }
  25     return myValue;
  26   }
  27
  28   protected abstract Value computeInternal() throws Exc;
  29 }