This finalize() method does not make a call to its superclass's finalize() method.  So, any finalizer actions defined for the superclass will not be performed.  Add a call to super.finalize().

The only thing this finalize() method does is call the superclass's finalize() method, making it redundant.  Delete it.

This empty finalize() method explicitly negates the effect of any finalizer defined by its superclass.  Any finalizer actions defined for the superclass will not be performed.  Unless this is intended, delete this method.

This finalizer nulls out fields. This is usually an error, as it does not aid garbage collection, and the object is going to be garbage collected anyway.

This finalizer does nothing except null out fields. This is completely pointless, and requires that the object be garbage collected, finalized, and then garbage collected again. You should just remove the finalize method.

This class implements the java.util.Iterator interface.  However, its next() method is not capable of throwing java.util.NoSuchElementException.  The next() method should be changed so it throws NoSuchElementException if is called when there are no more elements to return.

The method in the subclass doesn't override a similar method in a superclass because the type of a parameter doesn't exactly match the type of the corresponding parameter in the superclass. For example, if you have:

import alpha.Foo;
public class A {
  public int f(Foo x) { return 17; }
}
----
import beta.Foo;
public class B extends A {
  public int f(Foo x) { return 42; }
  public int f(alpha.Foo x) { return 27; }
}

The f(Foo) method defined in class B doesn't override the f(Foo) method defined in class A, because the argument types are Foo's from different packages.

In this case, the subclass does define a method with a signature identical to the method in the superclass, so this is presumably understood. However, such methods are exceptionally confusing. You should strongly consider removing or deprecating the method with the similar but not identical signature.

This method returns a value that is not checked. The return value should be checked since it can indicate an unusual or unexpected function execution. For example, the File.delete() method returns false if the file could not be successfully deleted (rather than throwing an Exception). If you don't check the result, you won't notice if the method invocation signals unexpected behavior by returning an atypical return value.

This method ignores the return value of one of the variants of java.io.InputStream.read() which can return multiple bytes.  If the return value is not checked, the caller will not be able to correctly handle the case where fewer bytes were read than the caller requested.  This is a particularly insidious kind of bug, because in many programs, reads from input streams usually do read the full amount of data requested, causing the program to fail only sporadically.

This method ignores the return value of java.io.InputStream.skip() which can skip multiple bytes.  If the return value is not checked, the caller will not be able to correctly handle the case where fewer bytes were skipped than the caller requested.  This is a particularly insidious kind of bug, because in many programs, skips from input streams usually do skip the full amount of data requested, causing the program to fail only sporadically. With Buffered streams, however, skip() will only skip data in the buffer, and will routinely fail to skip the requested number of bytes.

This code invokes a method that requires a security permission check. If this code will be granted security permissions, but might be invoked by code that does not have security permissions, then the invocation needs to occur inside a doPrivileged block.

Never call System.runFinalizersOnExit or Runtime.runFinalizersOnExit for any reason: they are among the most dangerous methods in the Java libraries. -- Joshua Bloch

The method creates a database resource (such as a database connection or row set), does not assign it to any fields, pass it to other methods, or return it, and does not appear to close the object on all paths out of the method.  Failure to close database resources on all paths out of a method may result in poor performance, and could cause the application to have problems communicating with the database.

The method creates a database resource (such as a database connection or row set), does not assign it to any fields, pass it to other methods, or return it, and does not appear to close the object on all exception paths out of the method.  Failure to close database resources on all paths out of a method may result in poor performance, and could cause the application to have problems communicating with the database.

The method creates an IO stream object, does not assign it to any fields, pass it to other methods that might close it, or return it, and does not appear to close the stream on all paths out of the method.  This may result in a file descriptor leak.  It is generally a good idea to use a finally block to ensure that streams are closed.

The method creates an IO stream object, does not assign it to any fields, pass it to other methods, or return it, and does not appear to close it on all possible exception paths out of the method.  This may result in a file descriptor leak.  It is generally a good idea to use a finally block to ensure that streams are closed.

This method might drop an exception.  In general, exceptions should be handled or reported in some way, or they should be thrown out of the method.

This method might ignore an exception.  In general, exceptions should be handled or reported in some way, or they should be thrown out of the method.

A method that returns either Boolean.TRUE, Boolean.FALSE or null is an accident waiting to happen. This method can be invoked as though it returned a value of type boolean, and the compiler will insert automatic unboxing of the Boolean value. If a null value is returned, this will result in a NullPointerException.

This class allocates an object that is based on a class that only supplies static methods. This object does not need to be created, just access the static methods directly using the class name as a qualifier.

This Serializable class is an inner class of a non-serializable class. Thus, attempts to serialize it will also attempt to associate instance of the outer class with which it is associated, leading to a runtime error.

If possible, making the inner class a static inner class should solve the problem. Making the outer class serializable might also work, but that would mean serializing an instance of the inner class would always also serialize the instance of the outer class, which it often not what you really want.

A non-serializable value is stored into a non-transient field of a serializable class.

This code creates a java.util.Random object, uses it to generate one random number, and then discards the Random object. This produces mediocre quality random numbers and is inefficient. If possible, rewrite the code so that the Random object is created once and saved, and each time a new random number is required invoke a method on the existing Random object to obtain it.

If it is important that the generated Random numbers not be guessable, you must not create a new Random for each random number; the values are too easily guessable. You should strongly consider using a java.security.SecureRandom instead (and avoid allocating a new SecureRandom for each random number needed).

This Serializable class is an inner class. Any attempt to serialize it will also serialize the associated outer instance. The outer instance is serializable, so this won't fail, but it might serialize a lot more data than intended. If possible, making the inner class a static inner class (also known as a nested class) should solve the problem.

This class defines a serialVersionUID field that is not final.  The field should be made final if it is intended to specify the version UID for purposes of serialization.