// The MIT License (MIT) // // Copyright (c) 2018 Robert C. Seacord // // Permission is hereby granted, free of charge, to any person obtaining a copy // of this software and associated documentation files (the "Software"), to deal // in the Software without restriction, including without limitation the rights // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell // copies of the Software, and to permit persons to whom the Software is // furnished to do so, subject to the following conditions: // // The above copyright notice and this permission notice shall be included in all // copies or substantial portions of the Software. // // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE // SOFTWARE. package MET11J; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.util.LinkedHashMap; class SerialHasher { public static void main(String[] args) throws IOException, ClassNotFoundException { MyKey key = new MyKey(1); LinkedHashMap<MyKey, String> ht = new LinkedHashMap<>(); ht.put(key, "Value"); System.out.println("Entry: " + ht.get(key)); // Retrieve using the key, works // Serialize the hash table object try (FileOutputStream fos = new FileOutputStream("hashdata.ser"); ObjectOutputStream oos = new ObjectOutputStream(fos)) { oos.writeObject(ht); } // Deserialize the hash table object LinkedHashMap<MyKey, String> ht_in; try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream("hashdata.ser"))) { ht_in = (LinkedHashMap <MyKey, String>) ois.readObject(); } if (ht_in.containsValue("Value")) // Check whether the object actually exists in the hash table System.out.println("Value was found in deserialized object."); // Can fail after serialization and deserialization. Consequently, // it may be impossible to retrieve the value of the object after // deserialization by using the original key. if (ht_in.get(key) == null) // Gets printed System.out.println("Object was not found when retrieved using the key."); } }