问如何使用JSch API发送UNIX命令？

EN

%   ftp test.cs.xxxx.edu  
Connected to test.cs.xxxx.edu.  
220 test FTP server (Version 5.53 ........) ready.  
Name (test.cs.xxxx.edu:yourlogin): yourlogin  
331 Password required for yourlogin.  
Password:  
230 User yourlogin logged in.  
ftp> cd HPSC/exercises  
ftp> get JHFLKDHLFKD.zip 

JSch jsch = new JSch();       

Session session_1 = jsch.getSession("user1", "host1", 22); 
session_1.setConfig("StrictHostKeyChecking", "no");
session_1.setPassword("pass1"); 
session_1.connect();
System.out.println("The session 1  has been established");

ChannelExec exec = (ChannelExec)session_1.openChannel("exec");

exec.connect(); 
exec.setCommand("ftp test.cs.xxxx.edu"); 
exec.setCommand("user2"); 
exec.setCommand("pass2"); 
exec.setCommand("cd \test\test\test"); 
exec.setCommand("get JHFLKDHLFKD.zip");