Find the greatest product of five consecutive digits in the 1000-digit number.

LargestProductOf_m_ConsecutiveDigits.java

public class LargestProductOf_m_ConsecutiveDigits {
	public static int calculate(String s,int m) throws Exception{
		int max=0;
		for(int i=0;i<=s.length()-m;i++){
			int prod=getProd(s, i, m);
			if(prod>max) max=prod;
		}
		return max;
	}
	private static int getProd(String s, int i,int m) throws Exception{
		int prod=1;
		for(int j=i;j<i+m && j<=s.length()-1;j++){
			if(s.charAt(i)<'0' || s.charAt(i)>'9') throw new Exception("Faulty string");
			prod*=(int)(s.charAt(j)-'0');
		}
		return prod;
		
	}
}

LargestProductOf_m_ConsecutiveDigitsTest.java

public class LargestProductOf_m_ConsecutiveDigitsTest {
	@Test
	public void testCalculate() throws Exception {
		assertEquals(0, LargestProductOf_m_ConsecutiveDigits.calculate("123", 5));
		assertEquals(120, LargestProductOf_m_ConsecutiveDigits.calculate("12345", 5));
		assertEquals(162, LargestProductOf_m_ConsecutiveDigits.calculate("12345099211", 5));
		assertEquals(40824, LargestProductOf_m_ConsecutiveDigits.calculate("7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450", 5));
	}
}