example.rb

require 'java'

class Example 

  java_annotation 'Deprecated'
  java_field "public java.lang.String abc"

  def test0
    to_java.abc = "quack"
  end

  def test1
    to_java.abc
  end

  def test2
    # for non-public
    f = to_java.java_class.get_declared_field('abc')
    f.accessible = true
    f.get(to_java)
  end

end

run.sh-session

$  jrubyc --java example.rb