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

@@ -1,10 +1,11 @@
 return {
-  {"nvim-treesitter/nvim-treesitter", build = ":TSUpdate"},
+  { "nvim-treesitter/nvim-treesitter", build = ":TSUpdate" },
+  { "mfussenegger/nvim-jdtls" },
   {
     "neovim/nvim-lspconfig",
     config = function()
       local lspconfig = require("lspconfig")
-      lspconfig.lua_ls.setup{}
+      lspconfig.lua_ls.setup {}
     end,
   },
   {
@@ -26,7 +27,7 @@ return {
       vim.api.nvim_create_autocmd('LspAttach', {
         desc = 'LSP actions',
         callback = function(event)
-          local opts = {buffer = event.buf}
+          local opts = { buffer = event.buf }
           vim.keymap.set('n', 'K', '<cmd>lua vim.lsp.buf.hover()<cr>', opts)
           vim.keymap.set('n', 'gd', '<cmd>lua vim.lsp.buf.definition()<cr>', opts)
           vim.keymap.set('n', 'gD', '<cmd>lua vim.lsp.buf.declaration()<cr>', opts)
@@ -35,7 +36,7 @@ return {
           vim.keymap.set('n', 'gr', '<cmd>lua vim.lsp.buf.references()<cr>', opts)
           vim.keymap.set('n', 'gs', '<cmd>lua vim.lsp.buf.signature_help()<cr>', opts)
           vim.keymap.set('n', '<F2>', '<cmd>lua vim.lsp.buf.rename()<cr>', opts)
-          vim.keymap.set({'n', 'x'}, '<F3>', '<cmd>lua vim.lsp.buf.format({async = true})<cr>', opts)
+          vim.keymap.set({ 'n', 'x' }, '<F3>', '<cmd>lua vim.lsp.buf.format({async = true})<cr>', opts)
           vim.keymap.set('n', '<F4>', '<cmd>lua vim.lsp.buf.code_action()<cr>', opts)
         end,
       })