We're stumped on getting this to work, despite considerable googling and experimentation.  Here's the item declaration:

 

    @EventHandler
    public void preinit(FMLPreInitializationEvent event) {
    		System.out.println("PRE-INITIALIZATION");
    		testItem = (Item)(new Item());
    		testItem.setRegistryName("stroutmod1_testitem1");
    		testItem.setUnlocalizedName(testItem.getRegistryName().toString());
    		testItem.setCreativeTab(CreativeTabs.MISC);
    		System.out.println("Registered item: " + testItem.getRegistryName());
    		ForgeRegistries.ITEMS.register(testItem);    		
    }

 

Note the println there showing us the registry name; when we launch, it shows "stroutmod1:stroutmod1_testitem1".

 

Now we have a en_US.lang file at stroutmod1/src/main/resources/assets/stroutmod1/lang/en_US.lang.  It's UTF-8 with no BOM, and contains:

item.stroutmod1:stroutmod1_testitem1.name=Test Item

 

Yet when we run the game, the item shows up as "item.stroutmod1:stroutmod1_testitem1.name" rather than "Test Item".

 

Any idea what we're missing?

You are modid:modid_testitem1 but you do are modid:testitem1 :

testItem.setRegistryName("testitem1");

41 minutes ago, JoeStrout said:

ForgeRegistries.ITEMS.register(testItem);

Never register things like this.
ForgeRegistries#<REGISTRY> are solely for querying & iterating over.
If you want to register an object, use the RegistryEvent's.

 

I believe that lang-file(en_US) have to be lower-case only(en_us) in 1.11+. @Choonster goes over why here.

 

48 minutes ago, Matryoshika said:

Never register things like this.
ForgeRegistries#<REGISTRY> are solely for querying & iterating over.
If you want to register an object, use the RegistryEvent's

Oops, looks like we must have found some old docs/samples.  I'll look into this right away.

 

50 minutes ago, Matryoshika said:

I believe that lang-file(en_US) have to be lower-case only(en_us) in 1.11+.

That's it!  Renaming the file to en_us.lang did the trick.

 

Thanks very much!