Code review cleanups

Library/Homebrew/extend/os/linux/requirements/java_requirement.rb

@@ -4,11 +4,8 @@ class JavaRequirement < Requirement
   default_formula "jdk"
 
   env do
-    next unless @java_home
     env_java_common
-    if (Pathname.new(@java_home)/"include").exist? # Oracle JVM
-      env_oracle_jdk
-    end
+    env_oracle_jdk
   end
 
   private

Library/Homebrew/extend/os/mac/requirements/java_requirement.rb

@@ -3,12 +3,7 @@ class JavaRequirement
 
   env do
     env_java_common
-    java_home = Pathname.new(@java_home)
-    if (java_home/"include").exist? # Oracle JVM
-      env_oracle_jdk
-    else # Apple JVM
-      env_apple
-    end
+    env_oracle_jdk || env_apple
   end
 
   private

Library/Homebrew/requirements/java_requirement.rb

@@ -83,15 +83,19 @@ class JavaRequirement < Requirement
   end
 
   def env_java_common
+    return unless @java_home
     java_home = Pathname.new(@java_home)
     ENV["JAVA_HOME"] = java_home
     ENV.prepend_path "PATH", java_home/"bin"
   end
 
   def env_oracle_jdk
+    return unless @java_home
     java_home = Pathname.new(@java_home)
+    return unless (java_home/"include").exist?
     ENV.append_to_cflags "-I#{java_home}/include"
     ENV.append_to_cflags "-I#{java_home}/include/#{oracle_java_os}"
+    true
   end
 
   def oracle_java_os