class Wire { private final float delay; // time delay of this wire private final Gate destination; // where wire goes, or null private final Gate source; // source of wire, or null // Wire name is the source-destination names /** Initializer scans and processes one wire definition. * @param sc The scanner from which the definition is read. */ public Wire( Scanner sc ) { // textual names of source and dest String srcName = ScanSupport.nextName( sc ); String dstName = ScanSupport.nextName( sc ); // if there are no next names on this line, these are "" // therefore, the findGate calls below will fail // lookup names of source and dest source = TernaryLogic.findGate( srcName ); if (source == null) { Errors.warn( "Wire '" + srcName + "' '" + dstName + "' source undefined." ); } destination = TernaryLogic.findGate( dstName ); if (destination == null) { Errors.warn( "Wire '" + srcName + "' '" + dstName + "' destination undefined." ); } delay = ScanSupport.nextFloat( sc ); if (delay != delay) { // really asks if delay == NaN Errors.warn( "Wire '" + srcName + "' '" + dstName + "' has no delay." ); } else if (delay  this.toString() ); // Now, tell the gates that they've been wired together if (destination != null) destination.addIncoming( this ); if (source != null) source.addOutgoing( this ); } /** Convert this wire to a format like that used for input * @return The textual description of the wire */ public String toString() { String srcName; String dstName; if (source == null) { srcName = "???"; } else { srcName = source.name; } if (destination == null) { dstName = "???"; } else { dstName = destination.name; } return( "wire " + srcName + " " + dstName + " " + delay ); } // ***** Logic Simulation ***** /** simulation class for an input change to this wire */ public static final class InputChangeEvent extends Simulation.Event { private final Wire w; // the wire with an input that changes private final int oldv; // the former value on w private final int newv; // the new value on w /** Construct an input change event * @param time the time at which the input changes. * @param w the wire where the input changes. * @param ov the previous logic value carried over w. * @param nv the new logic value carried over w. */ public InputChangeEvent( float time, Wire w, int ov, int nv) { super( time ); this.w = w; this.oldv = ov; this.newv = nv; } /** Every event must provide a trigger method */ public void trigger() { Simulation.schedule( new OutputChangeEvent( time + w.delay, w, oldv, newv ) ); } }; /** simulation class for an output change to this wire */ public static final class OutputChangeEvent extends Simulation.Event { private final Wire w; // the wire with an output that changes private final int oldv; // the former value on w private final int newv; // the new value on w /** Construct an output change event * @param time the time at which the output changes. * @param w the wire where the output changes. * @param ov the previous logic value carried over w. * @param nv the new logic value carried over w. */ public OutputChangeEvent( float time, Wire w, int ov, int nv ) { super( time ); this.w = w; this.oldv = ov; this.newv = nv; } /** Every event must provide a trigger method */ public void trigger() { Simulation.schedule( new Gate.InputChangeEvent( time, w.destination, oldv, newv ) ); } } } 

Background: Look at class Wire in the code distributed for for MP6. in a) One of the simulation classes can be private. Which one, and why must the other one remain public? (0.5 point)