How are Java source code files named

A Java source code file takes the name of a public class or interface that is defined withinthe file. A source code file may contain at most one public class or interface. If a publicclass or interface is defined within a source code file, then the source code file must takethe name of the public class or interface. If no public class or interface is defined within asource code file, then the file must take on a name that is different than its classes andinterfaces. Source code files use the .java extension.