Java Q & A: use the Factory Method mode (convert)

Java Q & A: use the Factory Method mode
Q: When I read the article "Polymorphism in its purest form", I saw an unfamiliar term "Factory method ". Can you explain what is Factory method and how to use it?
A: Factory method is just the name of A method for instantiating an object. Like a Factory, a Factory method task is to create -- or manufacture -- objects.
Let's look at an example.
Each program must have an error reporting method. Take a look at the following interface:
Code List 1
Public interface Trace {
// Turn on and off debugging
Public void setDebug (boolean debug );
// Write out a debug message
Public void debug (String message );
// Write out an error message
Public void error (String message );
}
Assume that two implementations are written. One implementation (code listing 3) writes information to the command line, and the other (code listing 2) writes information to the file.
Code List 2
Public class FileTrace implements Trace {

Private java. io. PrintWriter pw;
Private boolean debug;
Public FileTrace () throws java. io. IOException {
// A real FileTrace wowould need to obtain the filename somewhere
// For the example I'll hardcode it
Pw = new java. io. PrintWriter (new java. io. FileWriter ("c: race. log "));
      }
Public void setDebug (boolean debug ){
This. debug = debug;
      }
Public void debug (String message ){