hamsterdb: use :java instead of custom requirement

Closes Homebrew/homebrew#37119.

Signed-off-by: Xu Cheng <xucheng@me.com>

Formula/hamsterdb.rb

@@ -1,28 +1,3 @@
-class JavaRequirement < Requirement
-  fatal true
-
-  def self.jdk_home
-    [
-      `/usr/libexec/java_home`.chomp,
-      ENV['JAVA_HOME']
-    ].find { |dir| dir && File.exist?("#{dir}/bin/javac") && File.exist?("#{dir}/include") }
-  end
-
-  satisfy :build_env => false do
-    self.class.jdk_home
-  end
-
-  def message; <<-EOS.undent
-    Could not find a JDK (i.e. not a JRE)
-
-    Do one of the following:
-    - install a JDK that is detected with /usr/libexec/java_home
-    - set the JAVA_HOME environment variable
-    - specify --without-java
-    EOS
-  end
-end
-
 class Hamsterdb < Formula
   homepage "http://hamsterdb.com"
   url "http://files.hamsterdb.com/dl/hamsterdb-2.1.9.tar.gz"
@@ -48,7 +23,7 @@ class Hamsterdb < Formula
 
   depends_on "boost"
   depends_on "gnutls"
-  depends_on JavaRequirement if build.with? "java"
+  depends_on :java => :recommended
   depends_on "protobuf" if build.with? "remote"
 
   resource "libuv" do
@@ -77,7 +52,7 @@ class Hamsterdb < Formula
     features = []
 
     if build.with? "java"
-      features << "JDK=#{JavaRequirement.jdk_home}"
+      features << "JDK=#{ENV["JAVA_HOME"]}"
     else
       features << "--disable-java"
     end