UI Extensions

You can customize the inputlist based picker that is used for code-actions and various other actions by overriding the require('jdtls.ui').pick_one_async function:

If using nvim-fzy:

lua require('jdtls.ui').pick_one_async = require('fzy').pick_one

If using telescope.nvim:

lua <<
local finders = require'telescope.finders'
local sorters = require'telescope.sorters'
local actions = require'telescope.actions'
local pickers = require'telescope.pickers'
require('jdtls.ui').pick_one_async = function(items, prompt, label_fn, cb)
  local opts = {}
  pickers.new(opts, {
    prompt_title = prompt,
    finder    = finders.new_table {
      results = items,
      entry_maker = function(entry)
        return {
          value = entry,
          display = label_fn(entry),
          ordinal = label_fn(entry),
        }
      end,
    },
    sorter = sorters.get_generic_fuzzy_sorter(),
    attach_mappings = function(prompt_bufnr)
      actions.select_default:replace(function()
        local selection = actions.get_selected_entry(prompt_bufnr)
        actions.close(prompt_bufnr)

        cb(selection.value)
      end)

      return true
    end,
  }):find()
end
EOF

If using nvim-lsputils:

local jdtls_ui = require'jdtls.ui'
function jdtls_ui.pick_one_async(items, _, _, cb)
  require'lsputil.codeAction'.code_action_handler(nil, nil, items, nil, nil, nil, cb)
end