public class Count3Quit {
	
	public static void main (String[] args) {
		boolean [] arr = new boolean [12580];
		int leftNum = arr.length;
		int flag = 0;
		int index = 0;
		
		for(int i = 0; i < arr.length; i++) {
			arr[i] = true;
		}
		
		while (leftNum > 1) {
			if(arr[index] == true) {
				flag++;
				if(flag == 3) {
					flag = 0;
					arr[index] = false;
					leftNum--;
				}
			}
			
			index++;
			
			if(index == arr.length)
				index = 0;
		}

		for(int i = 0; i < arr.length; i++) {
			if(arr[i] == true)
				System.out.println(i);
		}
		
	}
	
}
 

<pre name="code" class="java">以上有參考尚學堂 馬士兵老師的程式碼，純粹是陣列那方面的知識

接著是一種利用面向物件思想的解決辦法，把500個數字看成是500個小人

</pre><pre name="code" class="java"><pre name="code" class="java">public class Count3Quit2 {
	
	public static void main (String[] args) {
		KidCircle kc = new KidCircle(500);
		int flag = 0;
		Kid k = kc.first;
		
		while(kc.count > 1) {
			flag++;
			if(flag == 3){
				kc.delete(k);
				flag = 0;
			}
			k = k.right;
			
		}
		
		System.out.println(kc.first.id);
		
	}
	
}

class Kid {
	int id;
	Kid left;
	Kid right;
	
}

class KidCircle {
	int count = 0;
	Kid first;
	Kid last;
	
	KidCircle (int n) {
		for(int i = 0; i < n; i++)
			add();
	}
	
	void add () {
		Kid k = new Kid();
		k.id = count;
		
		if (count <= 0) {
			k.left = k;
			k.right = k;
			first = k;
			last = k;
		}
		
		else {
			last.right = k;
			first.left = k;
			k.left = last;
			k.right = first;
			last = k;
		}
		
		count ++;
	}
	
	void delete(Kid k) {
		if (count <= 0)
			return;
		
		else if (count == 1) {
			last = first = null;
		}
		
		else {
			k.left.right = k.right;
			k.right.left = k.left;
			
			if (k == first) {
				first = k.right;
			}
			else if (k == last) {
				last = k.left;
			}
		}
		
		count --;
	}
	
	
	
}