diff -r 000000000000 -r 724f3e1ea53e emul/compact/src/main/java/java/math/SignedMutableBigInteger.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/emul/compact/src/main/java/java/math/SignedMutableBigInteger.java	Sat Sep 07 13:51:24 2013 +0200
@@ -0,0 +1,135 @@
+/*
+ * Copyright (c) 1999, 2007, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ */
+
+package java.math;
+
+/**
+ * A class used to represent multiprecision integers that makes efficient
+ * use of allocated space by allowing a number to occupy only part of
+ * an array so that the arrays do not have to be reallocated as often.
+ * When performing an operation with many iterations the array used to
+ * hold a number is only increased when necessary and does not have to
+ * be the same size as the number it represents. A mutable number allows
+ * calculations to occur on the same number without having to create
+ * a new number for every step of the calculation as occurs with
+ * BigIntegers.
+ *
+ * Note that SignedMutableBigIntegers only support signed addition and
+ * subtraction. All other operations occur as with MutableBigIntegers.
+ *
+ * @see     BigInteger
+ * @author  Michael McCloskey
+ * @since   1.3
+ */
+
+class SignedMutableBigInteger extends MutableBigInteger {
+
+   /**
+     * The sign of this MutableBigInteger.
+     */
+    int sign = 1;
+
+    // Constructors
+
+    /**
+     * The default constructor. An empty MutableBigInteger is created with
+     * a one word capacity.
+     */
+    SignedMutableBigInteger() {
+        super();
+    }
+
+    /**
+     * Construct a new MutableBigInteger with a magnitude specified by
+     * the int val.
+     */
+    SignedMutableBigInteger(int val) {
+        super(val);
+    }
+
+    /**
+     * Construct a new MutableBigInteger with a magnitude equal to the
+     * specified MutableBigInteger.
+     */
+    SignedMutableBigInteger(MutableBigInteger val) {
+        super(val);
+    }
+
+   // Arithmetic Operations
+
+   /**
+     * Signed addition built upon unsigned add and subtract.
+     */
+    void signedAdd(SignedMutableBigInteger addend) {
+        if (sign == addend.sign)
+            add(addend);
+        else
+            sign = sign * subtract(addend);
+
+    }
+
+   /**
+     * Signed addition built upon unsigned add and subtract.
+     */
+    void signedAdd(MutableBigInteger addend) {
+        if (sign == 1)
+            add(addend);
+        else
+            sign = sign * subtract(addend);
+
+    }
+
+   /**
+     * Signed subtraction built upon unsigned add and subtract.
+     */
+    void signedSubtract(SignedMutableBigInteger addend) {
+        if (sign == addend.sign)
+            sign = sign * subtract(addend);
+        else
+            add(addend);
+
+    }
+
+   /**
+     * Signed subtraction built upon unsigned add and subtract.
+     */
+    void signedSubtract(MutableBigInteger addend) {
+        if (sign == 1)
+            sign = sign * subtract(addend);
+        else
+            add(addend);
+        if (intLen == 0)
+             sign = 1;
+    }
+
+    /**
+     * Print out the first intLen ints of this MutableBigInteger's value
+     * array starting at offset.
+     */
+    public String toString() {
+        return this.toBigInteger(sign).toString();
+    }
+
+}