字符串所有子串（Java）

public class SumNumString {
	
	
	public static int sumOfString(String str) {
		if(str == null || str.length() <=0 )
			return 0;
		
		int sum = 0;
		
		for(int i = 0; i < str.length(); i++ ) {
			for(int j = i+1; j<=str.length(); j++) {
				String substr = str.substring(i,j);
				System.out.print(substr+" ");
				int num = Integer.parseInt(substr);
				sum += num;
			}
		}
		
		
		return sum;
	}

	public static void main(String[] args) {
		
		System.out.println(sumOfString("147"));

	}

}