Just use a regular builder

src/main/java/net/minecraft/commands/CommandDispatcher.java

@@ -10,16 +10,11 @@ import java.util.Map;
 public class CommandDispatcher {
     private final Map<String, Runnable> commands = Maps.newHashMap();
 
-    public CommandBuilder createCommand(final String name) {
-        return new CommandBuilder() {
-            @Override
-            public void onFinish() {
-                if (commands.containsKey(name)) {
-                    throw new IllegalArgumentException("New command " + name + " conflicts with existing command " + name);
-                }
-                commands.put(name, getCommandExecutor());
-            }
-        };
+    public void register(CommandBuilder command) {
+        if (commands.containsKey(command.getName())) {
+            throw new IllegalArgumentException("New command " + command.getName() + " conflicts with existing command " + command.getName());
+        }
+        commands.put(command.getName(), command.getExecutor());
     }
 
     public void execute(String command) throws CommandException {

src/main/java/net/minecraft/commands/builder/CommandBuilder.java

@@ -1,28 +1,27 @@
 package net.minecraft.commands.builder;
 
-public abstract class CommandBuilder {
-    private boolean finished;
-    private Runnable commandExecutor;
+public class CommandBuilder {
+    private final String name;
+    private Runnable executor;
 
-    public void finish() {
-        if (finished) {
-            throw new IllegalStateException("Cannot finish() multiple times!");
-        }
-        if (commandExecutor == null) {
-            throw new IllegalStateException("Cannot finish() without a command executor!");
-        }
-        onFinish();
-        finished = true;
+    protected CommandBuilder(String name) {
+        this.name = name;
     }
 
-    protected abstract void onFinish();
+    public static CommandBuilder command(String name) {
+        return new CommandBuilder(name);
+    }
 
-    public CommandBuilder executes(Runnable runnable) {
-        this.commandExecutor = runnable;
+    public String getName() {
+        return name;
+    }
+
+    public CommandBuilder executes(Runnable executor) {
+        this.executor = executor;
         return this;
     }
 
-    public Runnable getCommandExecutor() {
-        return commandExecutor;
+    public Runnable getExecutor() {
+        return executor;
     }
 }