Merge pull request #9427 from alimate/BAEL-4153

BAEL-4153: Polluting the Heap

core-java-modules/core-java-lang-syntax/src/test/java/com/baeldung/varargs/HeapPollutionUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.varargs;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class HeapPollutionUnitTest {
+
+    @Test(expected = ClassCastException.class)
+    public void givenGenericVararg_whenUsedUnsafe_shouldThrowClassCastException() {
+        String one = firstOfFirst(Arrays.asList("one", "two"), Collections.emptyList());
+
+        assertEquals("one", one);
+    }
+
+    @Test(expected = ClassCastException.class)
+    public void givenGenericVararg_whenRefEscapes_mayCauseSubtleBugs() {
+        String[] args = returnAsIs("One", "Two");
+    }
+
+    private static String firstOfFirst(List<String>... strings) {
+        List<Integer> ints = Collections.singletonList(42);
+        Object[] objects = strings;
+        objects[0] = ints;
+
+        return strings[0].get(0);
+    }
+
+    private static <T> T[] toArray(T... arguments) {
+        return arguments;
+    }
+
+    private static <T> T[] returnAsIs(T a, T b) {
+        return toArray(a, b);
+    }
+}