While loop problem

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November 14th, 2012, 10:20 PM

lisa92

Contributing User

Join Date: Oct 2011

Posts: 43

Time spent in forums: 10 h 31 m 45 sec
Reputation Power: 2

While loop problem

Object is supposed to change mode (movement algorithm) depending on the time elapsed (switch btw chase or scatter). I created an while loop but the object moves only in one mode.

Code:

	//////
	private static int seconds=0;
	private static boolean ghostalive;
	
	protected static final int chaseMode = 0;
	protected static final int scatterMode = 1;
	protected static final int frightenedMode = 2;
	
	static int mode; //initially ghost start in scatterMode
 
	public Ghost(int x, int y, Maze maze){
		super(x, y, maze);
		futureDirection = 0;
		timer = 0;
		mode = getMode();
	}     
	
	public static int getMode(){
		mode=setMode();
		return mode;
	}

	//LEVEL 1
	//scatter for 7s 
	//chase for 20s 
	//scatter for 7s 
	//chase for 20s 
	//scatter for 5s 
	//chase for 20s
	//scatter for 5s 
	//chase indefinite

	public static int setMode(){
		
	while(ghostalive){
		
		mode = scatterMode;
		if(seconds>7)
			mode = chaseMode;//chaseMode=true;
		if(seconds>27)
			mode = scatterMode;
		if(seconds>34)
			mode = chaseMode;
		if(seconds>54) 
			mode = scatterMode;
		if(seconds>59) 
			mode = chaseMode;
		if(seconds>79)
			mode = scatterMode;
		if(seconds>84)
			mode = chaseMode;
		
		seconds++;
		
	}	return mode;
	}

November 14th, 2012, 11:04 PM

Jacques1

pollyanna

Join Date: Jul 2012

Location: Germany

Posts: 1,875

Time spent in forums: 1 Month 2 Weeks 2 Days 4 h 14 m 32 sec
Reputation Power: 813

Hi,

when you say that some objects move I guess there's code in a separate thread? Otherwise this wouldn't make sense at all.

Your mistake is that you assume the "seconds" counter actually determines the number of seconds. But Java will process a loop iteration in an instance, so the whole thing is over before you even notice it. You'll need something like Thread.sleep() to actually wait a second.

And you should follow naming conventions. A "set" or "get" methods are supposed to do nothing but "set" and "get" a variable (like the name suggests). Any other logic should be named differently.

November 15th, 2012, 04:11 AM

Aurum84

Contributing User

Join Date: Nov 2012

Posts: 74

Time spent in forums: 3 Days 23 h 5 m 49 sec
Reputation Power: 17

Jacques1 is right here. Even though you named a variable 'seconds', does not imply that it actually *is* a second.
I ran your code, and the Ghost perfectly outputs the behaviour you expected in the command-line.
The issue you have here is that the code is executed in a split-second, also because it all is calculated in the constructor, resulting in that you only perceive the last mode of the Ghost. To resolve this: make the Ghost a Thread

There are some other issues, besides Jacques1 mentioned:

A get/set method should do only just that. put the Ghost logic in another method, for example: updateMode.
Your current setMethod references and updates the variable 'mode' and returns it. It does not need to return it, since it is a variable accessible by the entire instance of Ghost. Therefore the code-part
Code:
```
mode=setMode();
```
can be changed to
Code:
```
setMode() //or: updateMode()
```
Change the large if-statement to an else-if construction, because only 1 clause can be true.

While loop problem

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