Add vscode-java-language-server linter

ale_linters/java/javalsp.vim

@@ -0,0 +1,28 @@
+" Author: Horacio Sanson <https://github.com/hsanson>
+" Description: Support for the Java language server https://github.com/georgewfraser/vscode-javac
+
+call ale#Set('java_javalsp_jar', 'javacs.jar')
+
+function! ale_linters#java#javalsp#Executable(buffer) abort
+    let l:jar = ale#VarFunc('java_javalsp_jar')(a:buffer)
+
+    if filereadable(l:jar)
+        return 'java'
+    endif
+
+    return ''
+endfunction
+
+function! ale_linters#java#javalsp#Command(buffer) abort
+    let l:jar = ale#VarFunc('java_javalsp_jar')(a:buffer)
+    return 'exec java -cp ' . l:jar . ' -Xverify:none org.javacs.Main'
+endfunction
+
+call ale#linter#Define('java', {
+\   'name': 'javalsp',
+\   'lsp': 'stdio',
+\   'executable_callback': 'ale_linters#java#javalsp#Executable',
+\   'command_callback': 'ale_linters#java#javalsp#Command',
+\   'language': 'java',
+\   'project_root_callback': 'ale#java#FindProjectRoot',
+\})