Disable frivolous PMD warnings and enable PMD in ntcore (#3419)

Some valid warnings like throwing NullPointerException or using a for
loop instead of System.arraycopy() were fixed.

Abstract classes marked with PMD.AbstractClassWithoutAbstractMethod were
made concrete because they already had protected constructors.

Fixes #1697.

wpilibOldCommands/src/main/java/edu/wpi/first/wpilibj/PIDBase.java

@@ -27,7 +27,6 @@ import java.util.concurrent.locks.ReentrantLock;
  * @deprecated All APIs which use this have been deprecated.
  */
 @Deprecated(since = "2020", forRemoval = true)
-@SuppressWarnings("PMD.TooManyFields")
 public class PIDBase implements PIDInterface, PIDOutput, Sendable, AutoCloseable {
   public static final double kDefaultPeriod = 0.05;
   private static int instances;
@@ -81,9 +80,6 @@ public class PIDBase implements PIDInterface, PIDOutput, Sendable, AutoCloseable
   private double m_setpoint;
   private double m_prevSetpoint;
 
-  @SuppressWarnings("PMD.UnusedPrivateField")
-  private double m_error;
-
   private double m_result;
 
   private LinearFilter m_filter;
@@ -199,7 +195,7 @@ public class PIDBase implements PIDInterface, PIDOutput, Sendable, AutoCloseable
    * Read the input, calculate the output accordingly, and write to the output. This should only be
    * called by the PIDTask and is created during initialization.
    */
-  @SuppressWarnings({"LocalVariableName", "PMD.ExcessiveMethodLength", "PMD.NPathComplexity"})
+  @SuppressWarnings("LocalVariableName")
   protected void calculate() {
     if (m_pidInput == null || m_pidOutput == null) {
       return;
@@ -291,7 +287,6 @@ public class PIDBase implements PIDInterface, PIDOutput, Sendable, AutoCloseable
       m_thisMutex.lock();
       try {
         m_prevError = error;
-        m_error = error;
         m_totalError = totalError;
         m_result = result;
       } finally {

wpilibOldCommands/src/main/java/edu/wpi/first/wpilibj/command/Command.java

@@ -36,7 +36,6 @@ import java.util.Enumeration;
  * @see CommandGroup
  * @see IllegalUseOfCommandException
  */
-@SuppressWarnings("PMD.GodClass")
 public abstract class Command implements Sendable, AutoCloseable {
   /** The time since this command was initialized. */
   private double m_startTime = -1;

wpilibOldCommands/src/main/java/edu/wpi/first/wpilibj/command/CommandGroup.java

@@ -30,13 +30,13 @@ import java.util.Vector;
  */
 public class CommandGroup extends Command {
   /** The commands in this group (stored in entries). */
-  @SuppressWarnings({"PMD.LooseCoupling", "PMD.UseArrayListInsteadOfVector"})
+  @SuppressWarnings("PMD.UseArrayListInsteadOfVector")
   private final Vector<Entry> m_commands = new Vector<>();
   /*
    * Intentionally package private
    */
   /** The active children in this group (stored in entries). */
-  @SuppressWarnings({"PMD.LooseCoupling", "PMD.UseArrayListInsteadOfVector"})
+  @SuppressWarnings("PMD.UseArrayListInsteadOfVector")
   final Vector<Entry> m_children = new Vector<>();
   /** The current command, -1 signifies that none have been run. */
   private int m_currentCommandIndex = -1;
@@ -205,7 +205,7 @@ public class CommandGroup extends Command {
   }
 
   @Override
-  @SuppressWarnings({"MethodName", "PMD.CyclomaticComplexity", "PMD.NPathComplexity"})
+  @SuppressWarnings("MethodName")
   void _execute() {
     Entry entry = null;
     Command cmd = null;

wpilibOldCommands/src/main/java/edu/wpi/first/wpilibj/command/Scheduler.java

@@ -15,6 +15,7 @@ import edu.wpi.first.wpilibj.smartdashboard.SendableBuilder;
 import edu.wpi.first.wpilibj.smartdashboard.SendableRegistry;
 import java.util.Enumeration;
 import java.util.Hashtable;
+import java.util.Map;
 import java.util.Vector;
 
 /**
@@ -46,8 +47,7 @@ public final class Scheduler implements Sendable, AutoCloseable {
   }
 
   /** A hashtable of active {@link Command Commands} to their {@link LinkedListElement}. */
-  @SuppressWarnings("PMD.LooseCoupling")
-  private final Hashtable<Command, LinkedListElement> m_commandTable = new Hashtable<>();
+  private final Map<Command, LinkedListElement> m_commandTable = new Hashtable<>();
   /** The {@link Set} of all {@link Subsystem Subsystems}. */
   private final Set m_subsystems = new Set();
   /** The first {@link Command} in the list. */
@@ -59,13 +59,12 @@ public final class Scheduler implements Sendable, AutoCloseable {
   /** Whether or not we are currently disabled. */
   private boolean m_disabled;
   /** A list of all {@link Command Commands} which need to be added. */
-  @SuppressWarnings({"PMD.LooseCoupling", "PMD.UseArrayListInsteadOfVector"})
+  @SuppressWarnings("PMD.UseArrayListInsteadOfVector")
   private final Vector<Command> m_additions = new Vector<>();
   /**
    * A list of all {@link edu.wpi.first.wpilibj.buttons.Trigger.ButtonScheduler Buttons}. It is
    * created lazily.
    */
-  @SuppressWarnings("PMD.LooseCoupling")
   private Vector<ButtonScheduler> m_buttons;
 
   private boolean m_runningCommandsChanged;
@@ -129,7 +128,7 @@ public final class Scheduler implements Sendable, AutoCloseable {
    *
    * @param command the {@link Command} to add
    */
-  @SuppressWarnings({"MethodName", "PMD.CyclomaticComplexity"})
+  @SuppressWarnings("MethodName")
   private void _add(Command command) {
     if (command == null) {
       return;
@@ -194,7 +193,6 @@ public final class Scheduler implements Sendable, AutoCloseable {
    *   <li>Add Defaults
    * </ol>
    */
-  @SuppressWarnings({"PMD.CyclomaticComplexity", "PMD.NPathComplexity"})
   public void run() {
     m_runningCommandsChanged = false;