Command::IsFinished() must be overriden by subclasses again (#353)

Documentation was added for InstantCommand and TimedCommand.

wpilibj/src/shared/java/edu/wpi/first/wpilibj/command/Command.java

@@ -277,16 +277,15 @@ public abstract class Command implements NamedSendable {
    * <p>It may be useful for a team to reference the {@link Command#isTimedOut() isTimedOut()}
    * method for time-sensitive commands.
    *
-   * <p>By default this will always return false, which means it will never end automatically. It
-   * may still be cancelled manually or interrupted by another command. For most real-world
-   * scenarios you will override this method with additional logic.
+   * <p>Returning false will result in the command never ending automatically. It may still be
+   * cancelled manually or interrupted by another command. Returning true will result in the
+   * command executing once and finishing immediately. We recommend using {@link InstantCommand}
+   * for this.
    *
    * @return whether this command is finished.
    * @see Command#isTimedOut() isTimedOut()
    */
-  protected boolean isFinished() {
-    return false;
-  }
+  protected abstract boolean isFinished();
 
   /**
    * Called when the command ended peacefully. This is where you may want to wrap up loose ends,

wpilibj/src/shared/java/edu/wpi/first/wpilibj/command/InstantCommand.java

@@ -7,10 +7,21 @@
 
 package edu.wpi.first.wpilibj.command;
 
+/**
+ * This command will execute once, then finish immediately afterward.
+ *
+ * <p>Subclassing {@link InstantCommand} is shorthand for returning true from
+ * {@link Command isFinished}.
+ */
 public class InstantCommand extends Command {
+
   public InstantCommand() {
   }
 
+  /**
+   * Creates a new {@link InstantCommand InstantCommand} with the given name.
+   * @param name the name for this command
+   */
   public InstantCommand(String name) {
     super(name);
   }

wpilibj/src/shared/java/edu/wpi/first/wpilibj/command/TimedCommand.java

@@ -7,6 +7,10 @@
 
 package edu.wpi.first.wpilibj.command;
 
+/**
+ * A {@link TimedCommand} will wait for a timeout before finishing.
+ * {@link TimedCommand} is used to execute a command for a given amount of time.
+ */
 public class TimedCommand extends Command {
   public TimedCommand(String name, double timeout) {
     super(name, timeout);