Java: Add test.

Author: aschackmull

java/ql/test/query-tests/UselessComparisonTest/B.java

@@ -0,0 +1,22 @@
+import java.util.*;
+import java.util.function.*;
+
+public class B {
+  int modcount = 0;
+
+  int[] arr;
+
+  public void modify(IntUnaryOperator func) {
+    int mc = modcount;
+    for (int i = 0; i < arr.length; i++) {
+      arr[i] = func.applyAsInt(arr[i]);
+    }
+    // Always false unless there is a call path from func.applyAsInt(..) to
+    // this method, but should not be reported, as checks guarding
+    // ConcurrentModificationExceptions are expected to always be false in the
+    // absence of API misuse.
+    if (mc != modcount)
+      throw new ConcurrentModificationException();
+    modcount++;
+  }
+}