when I hit M-x and write 'ensime' I get an error
`flet' is an obsolete macro (as of 24.3); use either `cl-flet' or `cl-letf'.
'let: Wrong type argument: arrayp, nil'
When I had 'require ensime' in _emacs, it told me something more:
Debugger entered--Lisp error: (wrong-type-argument arrayp nil)
file-truename(nil)
(let ((java (file-truename (executable-find "javac")))) (warn "JDK_HOME and JAVA_HOME are not set, inferring from %s" java) (ensime--parent-dir (ensime--parent-dir java)))
(cond ((getenv "JDK_HOME")) ((getenv "JAVA_HOME")) ((file-exists-p "/usr/libexec/java_home") (s-chomp (shell-command-to-string "/usr/libexec/java_home"))) ((quote t) (let ((java (file-truename (executable-find "javac")))) (warn "JDK_HOME and JAVA_HOME are not set, inferring from %s" java) (ensime--parent-dir (ensime--parent-dir java)))))
eval((cond ((getenv "JDK_HOME")) ((getenv "JAVA_HOME")) ((file-exists-p "/usr/libexec/java_home") (s-chomp (shell-command-to-string "/usr/libexec/java_home"))) ((quote t) (let ((java (file-truename (executable-find "javac")))) (warn "JDK_HOME and JAVA_HOME are not set, inferring from %s" java) (ensime--parent-dir (ensime--parent-dir java))))))
custom-initialize-reset(ensime-default-java-home (cond ((getenv "JDK_HOME")) ((getenv "JAVA_HOME")) ((file-exists-p "/usr/libexec/java_home") (s-chomp (shell-command-to-string "/usr/libexec/java_home"))) ((quote t) (let ((java (file-truename (executable-find "javac")))) (warn "JDK_HOME and JAVA_HOME are not set, inferring from %s" java) (ensime--parent-dir (ensime--parent-dir java))))))
custom-declare-variable(ensime-default-java-home (cond ((getenv "JDK_HOME")) ((getenv "JAVA_HOME")) ((file-exists-p "/usr/libexec/java_home") (s-chomp (shell-command-to-string "/usr/libexec/java_home"))) ((quote t) (let ((java (file-truename (executable-find "javac")))) (warn "JDK_HOME and JAVA_HOME are not set, inferring from %s" java) (ensime--parent-dir (ensime--parent-dir java))))) "Location of the JDK's base directory" :type string :group ensime-server)
eval-buffer(#<buffer *load*-216581> nil "c:/Users/leokr_000/AppData/Roaming/.emacs.d/elpa/ensime-20141007.246/ensime-vars.el" nil t) ; Reading at buffer position 2344
load-with-code-conversion("c:/Users/leokr_000/AppData/Roaming/.emacs.d/elpa/ensime-20141007.246/ensime-vars.el" "c:/Users/leokr_000/AppData/Roaming/.emacs.d/elpa/ensime-20141007.246/ensime-vars.el" nil t)
require(ensime-vars)
eval-buffer(#<buffer *load*-524611> nil "c:/Users/leokr_000/AppData/Roaming/.emacs.d/elpa/ensime-20141007.246/ensime.el" nil t) ; Reading at buffer position 1766
load-with-code-conversion("c:/Users/leokr_000/AppData/Roaming/.emacs.d/elpa/ensime-20141007.246/ensime.el" "c:/Users/leokr_000/AppData/Roaming/.emacs.d/elpa/ensime-20141007.246/ensime.el" nil t)
require(ensime)
eval-buffer(#<buffer *load*> nil "c:/Users/leokr_000/AppData/Roaming/_emacs" nil t) ; Reading at buffer position 220
load-with-code-conversion("c:/Users/leokr_000/AppData/Roaming/_emacs" "c:/Users/leokr_000/AppData/Roaming/_emacs" t t)
load("~/_emacs" t t)
#[0 "\205\262
This "_emacs" file was in fact copied from here https://github.com/ensime/ensime-server/wiki/Quick-Start-Guide I am running Windows 8 and emacs 24.3.
Apparently, Emas can't find your javac executable. Make sure you do have javac (or javac.exe maybe for your platform) somewhere and this this somewhere is listed in exec-path. Detailed explanation:
Debugger entered--Lisp error: (wrong-type-argument arrayp nil)
This says that the code tried to treat nil as if it were an array (a string is also an array).
file-truename(nil)
This says that it happened while calling file-truename with argument nil, and indeed, file-truename takes a file name (a string) as argument, so nil is not a valid argument for it.
(let ((java (file-truename (executable-find "javac"))))
This says that it happened while evaluating this code, where we see that the arg to file-truename is actually the value returned by (executable-find "javac") and this expression should return either the absolute file name of javac (as found in exec-path), or nil if it can't find it.