Reject overflowing digit recompositions

src/main/java/kyu7/DescendingOrder.java

@@ -18,12 +18,12 @@
             arrayList.add(i);
         }
         arrayList.sort(Comparator.reverseOrder());
-        int result = 0;
+        StringBuilder result = new StringBuilder();
         for (int i : arrayList
         ) {
-            result = result * 10 + i;
+            result.append(i);
         }
-        return result;
+        return Integer.parseInt(result.toString());
     }
 
 }

src/main/java/kyu7/MinimumLine.java

@@ -2,17 +2,20 @@
 
 
 import java.util.Arrays;
+import java.util.stream.Collectors;
 
 
 public class MinimumLine {
 
     // 7 https://www.codewars.com/kata/5ac6932b2f317b96980000ca/train/java
 
     public static int minValue(int[] values) {
-        return Arrays.stream(values)
+        String result = Arrays.stream(values)
                 .sorted()
                 .distinct()
-                .reduce(0, (result, digit) -> result * 10 + digit);
+                .mapToObj(String::valueOf)
+                .collect(Collectors.joining());
+        return Integer.parseInt(result);
     }
 
 }

src/test/java/kyu7/DescendingOrderTest.java

@@ -17,6 +17,11 @@
 import static kyu7.DescendingOrder.*;
 @Tag("smoke")
 public class DescendingOrderTest {
+    @Test
+    void rejectsReorderedValuesOutsideIntegerRange() {
+        assertThrows(NumberFormatException.class, () -> sortDesc(2_147_483_647));
+    }
+
     @Test
     void smokeTestsShouldExecuteApi() {
         quality.SmokeMethodTestHarness.verify(kyu7.DescendingOrder.class);

src/test/java/kyu7/MinimumLineTest.java

@@ -17,6 +17,13 @@
 import static kyu7.MinimumLine.*;
 @Tag("smoke")
 public class MinimumLineTest {
+    @Test
+    void rejectsConcatenatedValuesOutsideIntegerRange() {
+        int[] values = {9, 8, 7, 6, 5, 4, 3, 2, 1, 99};
+
+        assertThrows(NumberFormatException.class, () -> minValue(values));
+    }
+
     @Test
     void smokeTestsShouldExecuteApi() {
         quality.SmokeMethodTestHarness.verify(kyu7.MinimumLine.class);