8289260: BigDecimal movePointLeft() and movePointRight() do not follow their API spec

Reviewed-by: darcy

Author: rgiulietti

src/java.base/share/classes/java/math/BigDecimal.java

@@ -2993,7 +2993,7 @@ public BigDecimal setScale(int newScale) {
      * @throws ArithmeticException if scale overflows.
      */
     public BigDecimal movePointLeft(int n) {
-        if (n == 0) return this;
+        if (n == 0 && scale >= 0) return this;
 
         // Cannot use movePointRight(-n) in case of n==Integer.MIN_VALUE
         int newScale = checkScale((long)scale + n);
@@ -3017,7 +3017,7 @@ public BigDecimal movePointLeft(int n) {
      * @throws ArithmeticException if scale overflows.
      */
     public BigDecimal movePointRight(int n) {
-        if (n == 0) return this;
+        if (n == 0 && scale >= 0) return this;
 
         // Cannot use movePointLeft(-n) in case of n==Integer.MIN_VALUE
         int newScale = checkScale((long)scale - n);

test/jdk/java/math/BigDecimal/MovePointTests.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8289260
+ */
+
+import java.math.BigDecimal;
+
+public class MovePointTests {
+
+    public static void main(String argv[]) {
+        BigDecimal bd;
+
+        bd = BigDecimal.valueOf(1, -3);
+        checkNotIdentical(bd, bd.movePointLeft(0));
+        checkNotIdentical(bd, bd.movePointRight(0));
+
+        bd = BigDecimal.valueOf(1, 0);
+        checkIdentical(bd, bd.movePointLeft(0));
+        checkIdentical(bd, bd.movePointRight(0));
+
+        bd = BigDecimal.valueOf(1, 3);
+        checkIdentical(bd, bd.movePointLeft(0));
+        checkIdentical(bd, bd.movePointRight(0));
+
+        bd = BigDecimal.valueOf(1, -3);
+        checkNotEquals(bd, bd.movePointLeft(1));
+        checkNotEquals(bd, bd.movePointLeft(-1));
+        checkNotEquals(bd, bd.movePointRight(1));
+        checkNotEquals(bd, bd.movePointRight(-1));
+
+        bd = BigDecimal.valueOf(1, 0);
+        checkNotEquals(bd, bd.movePointLeft(1));
+        checkNotEquals(bd, bd.movePointLeft(-1));
+        checkNotEquals(bd, bd.movePointRight(1));
+        checkNotEquals(bd, bd.movePointRight(-1));
+
+        bd = BigDecimal.valueOf(1, 3);
+        checkNotEquals(bd, bd.movePointLeft(1));
+        checkNotEquals(bd, bd.movePointLeft(-1));
+        checkNotEquals(bd, bd.movePointRight(1));
+        checkNotEquals(bd, bd.movePointRight(-1));
+
+        bd = BigDecimal.valueOf(1, -3);
+        checkNotEquals(bd, bd.movePointLeft(10));
+        checkNotEquals(bd, bd.movePointLeft(-10));
+        checkNotEquals(bd, bd.movePointRight(10));
+        checkNotEquals(bd, bd.movePointRight(-10));
+
+        bd = BigDecimal.valueOf(1, 0);
+        checkNotEquals(bd, bd.movePointLeft(10));
+        checkNotEquals(bd, bd.movePointLeft(-10));
+        checkNotEquals(bd, bd.movePointRight(10));
+        checkNotEquals(bd, bd.movePointRight(-10));
+
+        bd = BigDecimal.valueOf(1, 3);
+        checkNotEquals(bd, bd.movePointLeft(10));
+        checkNotEquals(bd, bd.movePointLeft(-10));
+        checkNotEquals(bd, bd.movePointRight(10));
+        checkNotEquals(bd, bd.movePointRight(-10));
+    }
+
+    private static void checkIdentical(BigDecimal bd, BigDecimal res) {
+        if (res != bd) {  // intentionally !=
+            throw new RuntimeException("Unexpected result " +
+                    bd + " != " + res);
+        }
+    }
+
+    private static void checkNotIdentical(BigDecimal bd, BigDecimal res) {
+        if (res == bd) {  // intentionally ==
+            throw new RuntimeException("Unexpected result " +
+                    bd + " == " + res);
+        }
+    }
+
+    private static void checkNotEquals(BigDecimal bd, BigDecimal res) {
+        if (res.equals(bd)) {
+            throw new RuntimeException("Unexpected result " +
+                    bd + ".equals(" + res + ")");
+        }
+    }
+
+}