Added exercise octal

config.json

@@ -31,7 +31,8 @@
     "rna-transcription",
     "sieve",
     "simple-cipher",
-    "pascals-triangle"	
+    "octal",
+    "pascals-triangle"
   ],
   "deprecated": [
   ],

octal/build.gradle

@@ -0,0 +1,11 @@
+apply plugin: "java"
+apply plugin: "eclipse"
+apply plugin: "idea"
+
+repositories {
+  mavenCentral()
+}
+
+dependencies {
+  testCompile "junit:junit:4.10"
+}

octal/example.java

@@ -0,0 +1,33 @@
+public class Octal {
+
+    private String octal;
+    private int decimal;
+
+    public Octal(String octal) {
+        this.octal = octal;
+        this.decimal = getDecimalFromOctal(octal);
+    }
+
+    public int getDecimal() {
+        return decimal;
+    }
+
+    private static int getDecimalFromOctal(String octal) {
+        if (!isValid(octal)) {
+            return 0;
+        }
+
+        int sum = 0;
+
+        for (int index = 0; index < octal.length(); index++) {
+            sum += Character.getNumericValue(octal.charAt(index)) * Math.pow(8, octal.length() - index - 1);
+        }
+
+        return sum;
+    }
+
+    private static boolean isValid(String binaryRepresentation) {
+        return binaryRepresentation.chars()
+                .allMatch(x -> Character.isDigit((char) x) && Character.getNumericValue((char) x) < 8);
+    }
+}

octal/src/main/java/Octal.java

@@ -0,0 +1,2 @@
+public class Octal {
+}

octal/src/test/java/OctalTest.java

@@ -0,0 +1,47 @@
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import java.util.Arrays;
+import java.util.Collection;
+
+import static org.junit.Assert.assertEquals;
+
+@RunWith(Parameterized.class)
+public class OctalTest {
+
+    private String input;
+    private int expectedOutput;
+
+    @Parameterized.Parameters
+    public static Collection<Object[]> data() {
+        return Arrays.asList(new Object[][]{
+                {"1", 1},
+                {"10", 8},
+                {"17", 15},
+                {"11", 9},
+                {"130", 88},
+                {"2047", 1063},
+                {"7777", 4095},
+                {"1234567", 342391},
+                {"carrot", 0},
+                {"8", 0},
+                {"9", 0},
+                {"6789", 0},
+                {"abc1z", 0},
+                {"011", 9}
+        });
+    }
+
+    public OctalTest(String input, int expectedOutput) {
+        this.input = input;
+        this.expectedOutput = expectedOutput;
+    }
+
+    @Test
+    public void test() {
+        Octal octal = new Octal(input);
+
+        assertEquals(expectedOutput, octal.getDecimal());
+    }
+}