54 lines
2.0 KiB
Java
54 lines
2.0 KiB
Java
/*
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* The MIT License
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* Copyright © 2014-2021 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.nullobject;
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/**
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* Null Object pattern replaces null values with neutral objects. Many times this simplifies
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* algorithms since no extra null checks are needed.
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*
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* <p>In this example we build a binary tree where the nodes are either normal or Null Objects. No
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* null values are used in the tree making the traversal easy.
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*/
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public class App {
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/**
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* Program entry point.
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*
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* @param args command line args
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*/
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public static void main(String[] args) {
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var root = new NodeImpl("1",
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new NodeImpl("11",
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new NodeImpl("111", NullNode.getInstance(), NullNode.getInstance()),
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NullNode.getInstance()
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),
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new NodeImpl("12",
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NullNode.getInstance(),
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new NodeImpl("122", NullNode.getInstance(), NullNode.getInstance())
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)
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);
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root.walk();
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}
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}
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