java - Java - 同期されたメソッドが正しく機能しない

Question

文字列の「*」で表される猫のスレッドが「.」で表されるマウスのスレッドに続くゲームをシミュレートするプログラムを実行する必要があります。これが私が作成した同期文字列クラスです

public class SynchronizedString {

public SynchronizedString(){
    Random rand=new Random();
    length=rand.nextInt(10)+10;  //random integer between 10 and 20
    theString=new ArrayList<Character>(); 
    for(int i=0; i<length; i++){
        theString.add(' ');
    }
    mouseIndex=rand.nextInt(length-1); //random initial position for the mouse
    theString.set(mouseIndex, '.');
    catIndex=rand.nextInt(length-1); //random initial position for the cat
    while(catIndex==mouseIndex){
        catIndex=rand.nextInt(length-1); 
    }
    theString.set(catIndex,'*');
}

public synchronized void set(int position){
    String name=Thread.currentThread().getName();

    while (occupied==true || occupiedReading==true){
        try{
            System.err.println(name+" attemped to write");
            wait(); //keep on waiting until theString is free to write
        } catch(InterruptedException e) {
            e.printStackTrace();
        } 
    } //end while
    occupied=true;
    if(name.equalsIgnoreCase("CAT"))
    {
        theString.set(catIndex,' ');
        theString.set(position,'*');
        catIndex=position;
    } 
    else if(name.equalsIgnoreCase("MOUSE")) 
    {
        theString.set(mouseIndex,' ');
        theString.set(position,'.');
        mouseIndex=position;
    }

    occupied=false;
    notifyAll();
}

public synchronized ArrayList<Character> get(){
    String name=Thread.currentThread().getName();

    while (occupied==true){
        try{
            System.err.println(name+" attemped to read");
            wait(); //keep on waiting until theString is free to write
        } catch(InterruptedException e) {
            e.printStackTrace();
        } 
    } //end while
    occupiedReading=true;

    occupiedReading=false;
    notifyAll();
    return theString;
}

public synchronized void print(){
    String name=Thread.currentThread().getName();
    while(printing)
        try {
            System.err.println(name + "attempted to print");
            wait();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    printing=true;

    System.out.println();
    for(Character c:theString){
        System.out.print(c.charValue());
    }
    System.out.println();

    printing=false;
    notify();
}

ArrayList<Character> theString;
private int length;
private int mouseIndex;
boolean printing;
private int catIndex;
private boolean occupied=false;
private boolean occupiedReading=false;

}

次に、Cat と Mouse の 2 つのスレッドを実行し続け、synchronizedString を読み取り、位置を変更して上書きします。

public class Cat extends Thread {
public Cat(SynchronizedString s){
    super("CAT");
    sharedString=s;
    catched=false;
    position=sharedString.get().indexOf('*');
}

public void run(){
    while(catched==false){
        if(position==sharedString.get().indexOf('.'));
            catched=true;
        toModify=sharedString.get();
        position=toModify.indexOf('*');
        if(position==(toModify.size()-1)){
            direction=false;
        }
        if(position==0){
            direction=true;
        }
        if(direction)
            position=position+1;
        else
            position=position-1;
        sharedString.set(position);
    }
}

boolean direction=true;
private ArrayList<Character> toModify;
boolean catched;
private int position;
private SynchronizedString sharedString;

そしてマウススレッド

public class Mouse extends Thread {
public Mouse(SynchronizedString s){
    super("MOUSE");
    sharedString=s;
    catched=false;
    position=sharedString.get().indexOf('.');
}

public void run(){
    while(catched==false){
        if(position==sharedString.get().indexOf('*'));
            catched=true;
        toModify=sharedString.get();
        position=toModify.indexOf('.');
        if(position==(toModify.size()-1))
            position=position-1;
        else if(position==0)
            position=position+1;
        else{
            Random rand=new Random();
            if(rand.nextBoolean())
                position=position+1;
            else
                position=position-1;
        }
        sharedString.set(position);
    }
}

private ArrayList<Character> toModify;
private boolean catched;
private int position;
private SynchronizedString sharedString;

同期された文字列を出力するために使用している表示クラスは次のとおりです

public class Display extends Thread {
public Display(SynchronizedString s){
    synchronizedString=s;
    toPrint=synchronizedString.get();
}

public void run(){
    while(toPrint.indexOf('.')!=toPrint.indexOf('*'))
    {
        try {
            sleep(100);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        toPrint=synchronizedString.get();
        System.out.println();
        for(Character c:toPrint){
            System.out.print(c.charValue());
        }
        System.out.println();
    }
}
ArrayList<Character> toPrint;
private SynchronizedString synchronizedString;

そして、ここでスレッドを開始します。

public class Demo {
public static void main(String[]args){
    SynchronizedString sharedString=new SynchronizedString();

    Display display=new Display(sharedString);
    Cat cat=new Cat(sharedString);
    Mouse mouse=new Mouse(sharedString);

    display.start();
    cat.start();
    mouse.start();
}

問題は、猫とネズミの両方が 1 回だけ移動し、その後は同じ位置にとどまることです。誰かがこの問題で私を助けることができますか?