Here you can find the source of readLong(ObjectInput in)
public static Long readLong(ObjectInput in) throws IOException
//package com.java2s; //License from project: Apache License import java.io.IOException; import java.io.ObjectInput; public class Main { public static Long readLong(ObjectInput in) throws IOException { return (in.readBoolean() ? null : new Long(in.readLong())); }/*from w w w . j a v a 2 s .com*/ }