add javadocs to Command class

common/src/main/java/me/lucko/luckperms/common/commands/abstraction/Command.java

@@ -34,43 +34,57 @@ import me.lucko.luckperms.common.commands.CommandResult;
 import me.lucko.luckperms.common.commands.sender.Sender;
 import me.lucko.luckperms.common.locale.LocalizedSpec;
 import me.lucko.luckperms.common.plugin.LuckPermsPlugin;
+import me.lucko.luckperms.common.utils.Predicates;
 
 import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.function.Predicate;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * An abstract command class
  *
- * @param <T> the type required by the {@link #execute(LuckPermsPlugin, Sender, Object, List, String)} method of this command
+ * @param <T> the argument type required by the command
  * @param <S> the type of any child commands
  */
 public abstract class Command<T, S> {
 
+    /**
+     * The commands specification.
+     *
+     * Contains details about usage, description, etc
+     */
+    @Nonnull
     private final LocalizedSpec spec;
 
     /**
      * The name of the command. Should be properly capitalised.
      */
+    @Nonnull
     private final String name;
 
     /**
      * The permission required to use this command. Nullable.
      */
+    @Nullable
     private final CommandPermission permission;
 
     /**
      * A predicate used for testing the size of the arguments list passed to this command
      */
-    private final Predicate<Integer> argumentCheck;
+    @Nonnull
+    private Predicate<Integer> argumentCheck = Predicates.alwaysFalse();
 
     /**
      * Child commands. Nullable.
      */
+    @Nullable
     private final List<Command<S, ?>> children;
 
-    public Command(LocalizedSpec spec, String name, CommandPermission permission, Predicate<Integer> argumentCheck, List<Command<S, ?>> children) {
+    public Command(@Nonnull LocalizedSpec spec, @Nonnull String name, @Nullable CommandPermission permission, @Nonnull Predicate<Integer> argumentCheck, @Nullable List<Command<S, ?>> children) {
         this.spec = spec;
         this.name = name;
         this.permission = permission;
@@ -78,32 +92,104 @@ public abstract class Command<T, S> {
         this.children = children == null ? null : ImmutableList.copyOf(children);
     }
 
-    public Command(LocalizedSpec spec, String name, CommandPermission permission, Predicate<Integer> argumentCheck) {
+    public Command(@Nonnull LocalizedSpec spec, @Nonnull String name, @Nullable CommandPermission permission, @Nonnull Predicate<Integer> argumentCheck) {
         this(spec, name, permission, argumentCheck, null);
     }
 
-    public Command(LocalizedSpec spec, String name, Predicate<Integer> argumentCheck) {
+    public Command(@Nonnull LocalizedSpec spec, @Nonnull String name, @Nonnull Predicate<Integer> argumentCheck) {
         this(spec, name, null, argumentCheck, null);
     }
 
-    public abstract CommandResult execute(LuckPermsPlugin plugin, Sender sender, T t, List<String> args, String label) throws CommandException;
-
-    public List<String> tabComplete(LuckPermsPlugin plugin, Sender sender, List<String> args) {
-        return Collections.emptyList();
-    }
-
+    /**
+     * Gets the commands spec.
+     *
+     * @return the command spec
+     */
+    @Nonnull
     public LocalizedSpec getSpec() {
         return this.spec;
     }
 
+    /**
+     * Gets the short name of this command
+     *
+     * <p>The result should be appropriately capitalised.</p>
+     *
+     * @return the command name
+     */
+    @Nonnull
     public String getName() {
         return this.name;
     }
 
+    /**
+     * Gets the permission required by this command, if present
+     *
+     * @return the command permission
+     */
+    @Nonnull
+    public Optional<CommandPermission> getPermission() {
+        return Optional.ofNullable(this.permission);
+    }
+
+    /**
+     * Gets the predicate used to validate the number of arguments provided to
+     * the command on execution
+     *
+     * @return the argument checking predicate
+     */
+    @Nonnull
     public Predicate<Integer> getArgumentCheck() {
         return this.argumentCheck;
     }
 
+    /**
+     * Gets the commands children
+     *
+     * @return any child commands
+     */
+    @Nonnull
+    public Optional<List<Command<S, ?>>> getChildren() {
+        return Optional.ofNullable(this.children);
+    }
+
+    /**
+     * Gets the commands description.
+     *
+     * @return the description
+     */
+    public String getDescription() {
+        return getSpec().description();
+    }
+
+    /**
+     * Gets the usage of this command.
+     * Will only return a non empty result for main commands.
+     *
+     * @return the usage of this command.
+     */
+    public String getUsage() {
+        String usage = getSpec().usage();
+        return usage == null ? "" : usage;
+    }
+
+    /**
+     * Gets the arguments required by this command
+     *
+     * @return the commands arguments
+     */
+    public Optional<List<Arg>> getArgs() {
+        return Optional.ofNullable(getSpec().args());
+    }
+
+    // Main execution method for the command.
+    public abstract CommandResult execute(LuckPermsPlugin plugin, Sender sender, T t, List<String> args, String label) throws CommandException;
+
+    // Tab completion method - default implementation is provided as some commands do not provide tab completions.
+    public List<String> tabComplete(LuckPermsPlugin plugin, Sender sender, List<String> args) {
+        return Collections.emptyList();
+    }
+
     /**
      * Sends a brief command usage message to the Sender.
      * If this command has child commands, the children are listed. Otherwise, a basic usage message is sent.
@@ -137,37 +223,12 @@ public abstract class Command<T, S> {
     }
 
     /**
-     * Returns if this command should be displayed in command listings, or "hidden"
+     * Gets if this command should be displayed in command listings, or "hidden"
      *
-     * @return if this command should be displayed in command listings, or "hidden"
+     * @return if the command should be displayed
      */
     public boolean shouldDisplay() {
         return true;
     }
 
-    public String getDescription() {
-        return this.spec.description();
-    }
-
-    /**
-     * Returns the usage of this command. Will only return a non empty result for main commands.
-     *
-     * @return the usage of this command.
-     */
-    public String getUsage() {
-        String usage = this.spec.usage();
-        return usage == null ? "" : usage;
-    }
-
-    public Optional<CommandPermission> getPermission() {
-        return Optional.ofNullable(this.permission);
-    }
-
-    public Optional<List<Arg>> getArgs() {
-        return Optional.ofNullable(this.spec.args());
-    }
-
-    public Optional<List<Command<S, ?>>> getChildren() {
-        return Optional.ofNullable(this.children);
-    }
 }

common/src/main/java/me/lucko/luckperms/common/commands/abstraction/MainCommand.java

@@ -42,6 +42,8 @@ import java.util.Optional;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.stream.Collectors;
 
+import javax.annotation.Nonnull;
+
 public abstract class MainCommand<T, I> extends Command<Void, T> {
 
     // equals 1 if the command doesn't take a mid argument, e.g. /lp log sub-command....
@@ -191,6 +193,7 @@ public abstract class MainCommand<T, I> extends Command<Void, T> {
         return getChildren().get().stream().anyMatch(sc -> sc.isAuthorized(sender));
     }
 
+    @Nonnull
     @Override
     public Optional<List<Command<T, ?>>> getChildren() {
         return super.getChildren();

common/src/main/java/me/lucko/luckperms/common/commands/impl/migration/MigrationMainCommand.java

@@ -45,6 +45,8 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.concurrent.locks.ReentrantLock;
 
+import javax.annotation.Nonnull;
+
 public class MigrationMainCommand extends MainCommand<Object, Object> {
     private static final Map<String, String> PLUGINS = ImmutableBiMap.<String, String>builder()
             // bukkit
@@ -69,6 +71,7 @@ public class MigrationMainCommand extends MainCommand<Object, Object> {
         super(CommandSpec.MIGRATION.spec(locale), "Migration", 1, null);
     }
 
+    @Nonnull
     @Override
     public synchronized Optional<List<Command<Object, ?>>> getChildren() {
         if (this.commands == null) {

sponge/src/main/java/me/lucko/luckperms/sponge/commands/SpongeMainCommand.java

@@ -53,6 +53,8 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.stream.Collectors;
 
+import javax.annotation.Nonnull;
+
 public class SpongeMainCommand extends Command<Void, LPSubjectData> {
     private final LPSpongePlugin plugin;
 
@@ -225,6 +227,7 @@ public class SpongeMainCommand extends Command<Void, LPSubjectData> {
         return this.subCommands.values().stream().flatMap(List::stream).collect(ImmutableCollectors.toList());
     }
 
+    @Nonnull
     @Override
     public Optional<List<Command<LPSubjectData, ?>>> getChildren() {
         return Optional.of(getSubCommands());