Added LargestFiveDigitNumber impl and TCs

src/test/java/io/github/sandeeplakka/codewars/kyu7/LargestFiveDigitNumber.java

@@ -0,0 +1,46 @@
+package io.github.sandeeplakka.codewars.kyu7;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/*
+Largest 5 digit number in a series
+
+In the following 6 digit number: 283910
+91 is the greatest sequence of 2 consecutive digits.
+
+In the following 10 digit number: 1234567890
+67890 is the greatest sequence of 5 consecutive digits.
+
+Complete the solution so that it returns the greatest sequence of
+five consecutive digits found within the number given.
+The number will be passed in as a string of only digits.
+It should return a five digit integer. The number passed may be as large as 1000 digits.
+Adapted from ProjectEuler.net
+
+Categories : Algorithms
+
+ */
+public class LargestFiveDigitNumber {
+    @Test
+    public void exampleTests() {
+        doTest("283910", 83910);
+        doTest("1234567890", 67890);
+        doTest("731674765", 74765);
+    }
+
+    private void doTest(String input, int expected) {
+        assertEquals(expected, solve(input));
+    }
+
+    public static int solve(final String digits) {
+        int startIdx = 0;
+        int val = 0;
+        for (int i = 0; i <= digits.length() - 5; i++) {
+            int thisVal = Integer.parseInt(digits.substring(startIdx + i, startIdx + i + 5));
+            val = Math.max(val, thisVal);
+        }
+        return val;
+    }
+}