test/java/io/Serializable/replaceWithNull/ReplaceWithNull.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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/* @test
 * @bug 4065313
 * @clean A ReplaceWithNull MyObjectOutputStream
 * @summary Ensure that it is okay to replace an object with null.
 */
import java.io.*;

class A { }

class MyObjectOutputStream extends ObjectOutputStream {
  public MyObjectOutputStream(OutputStream out) throws IOException {
    super(out);
    enableReplaceObject(true);
  }
  protected Object replaceObject(Object obj) throws IOException {
    if(obj instanceof A) return null;
    else return obj;
  }
}

public class ReplaceWithNull {
    public static void main(String args[]) throws IOException {
        A a = new A();

        MyObjectOutputStream out =
            new MyObjectOutputStream(new ByteArrayOutputStream());
        out.writeObject(a);     //raised NullPointerException.
        out.close();
    }
}