单项选择题 11. public static void test（String str） {  12. if（str == null | str.lellgth（） == 0） {  13. System.out.println（”String is empty”）；  14. } else {  15. System.out.println（”String is not empty”）；  16. }  17. }  And the invocation：  31. test（llull）；  What is the result？（）

单项选择题 A UNIX user named Bob wants to replace his chess program with a new one， but he is hot sure where the old one is installed. Bob is currently able to run a Java chess program starting from his home directory /home/bob using the command：  java -classpath /test：/home/bob/downloads/* .jar games.Chess  Bobs CLASSPATH is set （at login time） to：  /usr/lib：/home/bob/classes：/opt/java/lib：/opt/java/lib/* .jar  What is a possible location for the Chess.class file？（）

多项选择题 package com.company.application；  public class MainClass {  public static void main（String[] args） { }  }  And MainClass exists in the /apps/com/company/application directory. Assume the CLASSPATH environment variable is set to “.“ （current directory）.  Which two java commands entered at the command line will run MainClass？（）