Would someone be able to help me please.
I am trying to complete exercise 13 from chapter 8 of the Art and Science of Java and have became stuck.
The program displays a set of towers (GRects), and then the user needs to click on any tower to have it send a signal to 'light (change the color)' the next tower in the chain. In the background with system.out I can see the signals being sent, however the event dispatcher waits (I read on another site) for this process to finish before updating the colors. Each object also has a time thread.sleep(300). My question is: Can someone please teach me how to write a new thread or show me what I am doing wrong and how I should go about fixing it. I have looked at Oracle docs on threads and can't understand what everything is, I am also new to Java and and doing self-study. While getting the exercise working is needed, I really want to learn how to make a program like this so that in the future I don't get stuck again. Any help from the online community would be greatly appreciated. Thank you in advance. The code:
/**
* Class name: SignalTower
* -----------------------
* This class defines a signal tower object that passes a message to the
* next tower in a line.
*
* Programmer:
* Date: 2015/12/25
*/
package com.chapter8;
import java.awt.Color;
import acm.graphics.GCompound;
import acm.graphics.GLabel;
import acm.graphics.GRect;
/* Class: SignalTower */
/**
* This class defines a signal tower object that passes a message
* to the next tower in a line.
*/
public class SignalTower extends GCompound {
GRect tower = new GRect(TOWER_WIDTH,TOWER_HEIGHT);
/* Constructor: SignalTower(name, link) */
/**
* Constructs a new signal tower with the following parameters:
*
* @param name The name of the tower
* @param link A link to the next tower, or null if none exists
*/
public SignalTower(String name, SignalTower link) {
towerName = name;
nextTower = link;
buildTower();
}
/* Method: signal() */
/**
* This method represents sending a signal to this tower. The effect
* is to light the signal fire here and to send an additional signal
* message to the next tower in the chain, if any.
*/
public void signal() {
lightCurrentTower();
if (nextTower != null) nextTower.signal();
}
/* Method: lightCurrentTower() */
/**
* This method lights the signal fire for this tower. This version
* supplies a temporary implementation (typically called a "stub")
* that simply prints the name of the tower to the standard output
* channel. If you wanted to redesign this class to be part of a
* graphical application, for example, you could override this
* method to draw an indication of the signal fire on the display.
*/
public void lightCurrentTower() {
try {
this.setTowerColor();
Thread.sleep(300);
} catch (InterruptedException e) {
// Handle here
}
System.out.println("Lighting " + towerName);
}
public void buildTower(){
tower.setFilled(false);
add(tower);
GLabel label = new GLabel(towerName);
label.setLocation(getTowerWidth()/2 - label.getWidth()/2, this.getTowerLabelY());
add(label);
}
public void setTowerColor(){
tower.setColor(Color.RED);
tower.setFillColor(Color.RED);
tower.setFilled(true);
}
public int getTowerWidth(){
return TOWER_WIDTH;
}
public int getTowerSpace(){
return TOWER_SPACE;
}
public int getTowerLabelY(){
return TOWER_LABEL_Y;
}
/* Private instance variables */
private String towerName; /* The name of this tower */
private SignalTower nextTower; /* A link to the next tower */
private static final int TOWER_WIDTH = 30;
private static final int TOWER_HEIGHT = 180;
private static final int TOWER_SPACE = 100;
private static final int TOWER_LABEL_Y = 200;
}
/**
* File name: BeaconsOfGondor.java
* -------------------------------
* Message passing in linked structures: The beacons of Gondor:
*
* For answer Gandalf cried aloud to his horse. “On, Shadowfax! We must hasten.
* Time is short. See! The beacons of Gondor are alight, calling for aid. War
* is kindled. See, there is the fire on Amon Dîn, and flame on Eilenach; and
* there they go speeding west: Nardol, Erelas, Min-Rimmon, Calenhad, and the
* Halifirien on the borders of Rohan.”
* —J. R. R. Tolkien, The Return of the King, 1955
*
* This program creates a graphical representation of linked structures using
* this example.
*
* Programmer: Peter Lock
* Date: 2016/1/5
*/
package com.chapter8;
import java.awt.Point;
import java.awt.event.MouseEvent;
import acm.program.GraphicsProgram;
public class BeaconsOfGondor extends GraphicsProgram implements Runnable{
private Object gobj;
public String flag = "";
SignalTower[] towers = new SignalTower[10];
SignalTower rohan = new SignalTower("Rohan", null);
SignalTower halifirien = new SignalTower("Halifirien", rohan);
SignalTower calenhad = new SignalTower("Calenhad", halifirien);
SignalTower minRimmon = new SignalTower("Min-Rimmon", calenhad);
SignalTower erelas = new SignalTower("Erelas", minRimmon);
SignalTower nardol = new SignalTower("Nardol", erelas);
SignalTower eilenach = new SignalTower("Eilenach", nardol);
SignalTower amonDin = new SignalTower("Amon Din", eilenach);
SignalTower minasTirith = new SignalTower("Minas Tirith", amonDin);
public void run(){
createTowers();
addMouseListeners();
// minasTirith.signal();
}
private void createTowers() {
add(minasTirith);
minasTirith.setLocation(minasTirith.getTowerSpace(), 30);
add(amonDin);
amonDin.setLocation(amonDin.getTowerSpace()*2, 30);
add(eilenach);
eilenach.setLocation(eilenach.getTowerSpace()*3, 30);
add(nardol);
nardol.setLocation(nardol.getTowerSpace()*4, 30);
add(erelas);
erelas.setLocation(erelas.getTowerSpace()*5, 30);
add(minRimmon);
minRimmon.setLocation(minRimmon.getTowerSpace()*6, 30);
add(calenhad);
calenhad.setLocation(calenhad.getTowerSpace()*7, 30);
add(halifirien);
halifirien.setLocation(halifirien.getTowerSpace()*8, 30);
add(rohan);
rohan.setLocation(rohan.getTowerSpace()*9, 30);
}
public void mousePressed(MouseEvent e) {
gobj = getElementAt(e.getX(), e.getY());
if(gobj != null){
Point mp = e.getPoint();
if(minasTirith.contains(mp.getX(), mp.getY())) minasTirith.signal();
if(amonDin.contains(mp.getX(), mp.getY())) amonDin.signal();
if(eilenach.contains(mp.getX(), mp.getY())) eilenach.signal();
if(nardol.contains(mp.getX(), mp.getY())) nardol.signal();
if(erelas.contains(mp.getX(), mp.getY())) erelas.signal();
if(minRimmon.contains(mp.getX(), mp.getY())) minRimmon.signal();
if(calenhad.contains(mp.getX(), mp.getY())) calenhad.signal();
if(halifirien.contains(mp.getX(), mp.getY())) halifirien.signal();
if(rohan.contains(mp.getX(), mp.getY())) rohan.signal();
}
}
}
