程式碼看著有點亂，有點複雜！單步除錯一下其實不復雜！當然前提是要搞清楚演算法的思想！

package yxd.sf.eightcoins;


public class EightCoins {

	public static int compareTo(int[] coins, int[] left, int[] right) {
		
		int leftTotal = 0;
		int rightTotal = 0;
		int fakeCoin = 0;
		int coinsSize = 0;
		
		if (coins.length % 2 == 0) {
			coinsSize = coins.length/2;			//將現在的硬幣分成兩半
			System.arraycopy(coins, 0, left, 0, coinsSize);		//前一半硬幣放到left
			for (int i = 0; i < coinsSize; i++) {
				leftTotal = leftTotal + left[i]; 		//前一半硬幣的總重量
			}
			System.arraycopy(coins, coinsSize, right, 0, coinsSize);		//後一半硬幣放到right
			for (int j = 0; j < coinsSize; j++) {
				rightTotal = rightTotal + right[j];			//後一半硬幣的總重量
			}
		}
		//比較right和left兩邊的硬幣重量
		if (leftTotal < rightTotal && coinsSize != 1) {			
			coins = right;
			int[] right_1 = new int[coinsSize/2];
			int[] left_1 = new int[coinsSize/2];
			right = right_1;		//動態改變陣列大小，減治後硬幣減半
			left = left_1;
			System.arraycopy(coins, 0, left, 0, coinsSize/2);
			System.arraycopy(coins, coinsSize/2, right, 0, coinsSize/2);
		} else if (leftTotal > rightTotal && coinsSize != 1) {
			coins = left;
			int[] right_1 = new int[coinsSize/2];
			int[] left_1 = new int[coinsSize/2];
			right = right_1;
			left = left_1;
			System.arraycopy(coins, 0, left, 0, coinsSize/2);
			System.arraycopy(coins, coinsSize/2, right, 0, coinsSize/2);
		}
		if (left.length != 1 && right.length != 1 && fakeCoin == 0) {
			fakeCoin = compareTo(coins, left, right);    //遞迴呼叫，如果不令“fakeCoin=”最終返回會為0
		}
		if (left.length == 1 && right.length == 1 && coinsSize == 2) {
			if (left[0] < right[0]) {
				fakeCoin = right[0];
			} else if (left[0] == right[0]){
				System.out.println(left[0] + "and" + right[0]);
			} else {
				fakeCoin = left[0];
			}
		}
		return fakeCoin;
	}
	public static void main(String[] args) {
		int[] coins = {1, 1, 1, 2, 1, 1, 1, 1};
		int[] left = new int[4];
		int[] right = new int[4];
		int flag = 0;
		int location = compareTo(coins, left, right);
		for (int i = 0; i < coins.length; i++) {
			flag++;
			if (coins[i] == location) {
				System.out.println("第" + flag + "枚硬幣為假幣！");
			}
		}
	}

}