add jdtls.

ftplugin/java.lua

@@ -0,0 +1,5 @@
+local config = {
+  cmd = { '/path/to/jdt-language-server/bin/jdtls' },
+  root_dir = vim.fs.dirname(vim.fs.find({ 'gradlew', '.git', 'mvnw' }, { upward = true })[1]),
+}
+require('jdtls').start_or_attach(config)

lua/plugins/lsp.lua

@@ -1,5 +1,6 @@
 return {
   { "nvim-treesitter/nvim-treesitter", build = ":TSUpdate" },
+  { "mfussenegger/nvim-jdtls" },
   {
     "neovim/nvim-lspconfig",
     config = function()