work of -z in unix

Question

if [ -z "${ABC}" ] 
then
LOGDIR=`${JAVA_HOME}/bin/java -cp ${a}/aim.jar my.app.util.GetLogDir "${rsp}"`

Can some one help me with this. What this if is exactly doing. Is it checking if abc exists and the calling GetLogDir's main with some arguments?

Answer 1

   -z string
              True if the length of string is zero.

To check whether ABC is empty. If it is then the command will be executed and result will be in the LOGDIR.

Answer 2

From man test:

 -z string                   True if  the  length  of  string
                             string is zero.