bundles/org.simantics.utils.datastructures/src/org/simantics/utils/datastructures/persistent/ImmutableStack.java

   1 /*******************************************************************************\r
   2  * Copyright (c) 2007, 2010 Association for Decentralized Information Management\r
   3  * in Industry THTH ry.\r
   4  * All rights reserved. This program and the accompanying materials\r
   5  * are made available under the terms of the Eclipse Public License v1.0\r
   6  * which accompanies this distribution, and is available at\r
   7  * http://www.eclipse.org/legal/epl-v10.html\r
   8  *\r
   9  * Contributors:\r
  10  *     VTT Technical Research Centre of Finland - initial API and implementation\r
  11  *******************************************************************************/\r
  12 package org.simantics.utils.datastructures.persistent;\r
  13 \r
  14 public abstract class ImmutableStack<T> {\r
  15         \r
  16         private ImmutableStack() {              \r
  17         }\r
  18         \r
  19         private static class SingleStackNode<T> extends ImmutableStack<T> {\r
  20                 ImmutableStack<T> parent;\r
  21                 T value;\r
  22                 \r
  23                 public SingleStackNode(ImmutableStack<T> parent, T value) {             \r
  24                         this.parent = parent;\r
  25                         this.value = value;\r
  26                 }\r
  27 \r
  28                 @Override\r
  29                 public T get(int i) {\r
  30                         return i==0 ? value : parent.get(i-1);\r
  31                 }       \r
  32         }\r
  33         \r
  34         private static class MultiStackNode<T> extends ImmutableStack<T> {\r
  35                 ImmutableStack<T> parent;\r
  36                 T[] values;\r
  37                 \r
  38                 public MultiStackNode(ImmutableStack<T> parent, T[] values) {           \r
  39                         this.parent = parent;\r
  40                         this.values = values;\r
  41                 }\r
  42 \r
  43                 @Override\r
  44                 public T get(int i) {\r
  45                         return i<values.length ? values[i] : parent.get(i-values.length);\r
  46                 }       \r
  47         }\r
  48         \r
  49         private static class EmptyStack<T> extends ImmutableStack<T> {\r
  50 \r
  51                 @Override\r
  52                 public T get(int i) {\r
  53                         throw new IllegalArgumentException("No such element in stack.");\r
  54                 }\r
  55                 \r
  56         }\r
  57         \r
  58         @SuppressWarnings({ "rawtypes" })\r
  59         static final EmptyStack EMPTY = new EmptyStack();\r
  60         \r
  61         public ImmutableStack<T> push(T value) {\r
  62                 return new SingleStackNode<T>(this, value);\r
  63         }\r
  64         \r
  65         public ImmutableStack<T> push(T[] values) {\r
  66                 if(values.length > 1)\r
  67                         return new MultiStackNode<T>(this, values);\r
  68                 else if(values.length == 1)\r
  69                         return new SingleStackNode<T>(this, values[0]);\r
  70                 else\r
  71                         return this;\r
  72         }\r
  73         \r
  74         public abstract T get(int i); \r
  75         \r
  76         @SuppressWarnings("unchecked")\r
  77         public static <T> ImmutableStack<T> empty() {\r
  78                 return (ImmutableStack<T>)EMPTY;\r
  79         }\r
  80         \r
  81         public static <T> ImmutableStack<T> of(T value) {\r
  82                 return new SingleStackNode<T>(null, value);\r
  83         }\r
  84         \r
  85         @SuppressWarnings("unchecked")\r
  86         public static <T> ImmutableStack<T> of(T[] values) {\r
  87                 if(values.length > 1)\r
  88                         return new MultiStackNode<T>((ImmutableStack<T>)empty(), values);\r
  89                 else if(values.length == 1)\r
  90                         return new SingleStackNode<T>((ImmutableStack<T>)empty(), values[0]);\r
  91                 else\r
  92                         return empty();\r
  93         }\r
  94 }\r