先定義為字串型別，字串相加只會增加字串的長度，將兩個字串相連。再轉化成整型相加求和即可。

public class Test8 {
	
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		System.out.print("請輸入相加的個數：");
		int n = s.nextInt();
		String num = "0";
		int sum = 0;
		
		for(int i = 0; i < n; i++) {
			num = num + 2;
			sum = sum + Integer.valueOf(num);
		}
		
		System.out.println(sum);
	}
}