6560935: BigInteger.modPow() throws ArithmeticException for negative exponent

Reviewed-by: alanb

jdk/src/share/classes/java/math/BigInteger.java

@@ -478,7 +478,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
 
     /**
      * Constructs a randomly generated BigInteger, uniformly distributed over
-     * the range {@code 0} to (2<sup>{@code numBits}</sup> - 1), inclusive.
+     * the range 0 to (2<sup>{@code numBits}</sup> - 1), inclusive.
      * The uniformity of the distribution assumes that a fair source of random
      * bits is provided in {@code rnd}.  Note that this constructor always
      * constructs a non-negative BigInteger.
@@ -1332,7 +1332,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
      *
      * @param  val value by which this BigInteger is to be divided.
      * @return {@code this / val}
-     * @throws ArithmeticException {@code val==0}
+     * @throws ArithmeticException if {@code val} is zero.
      */
     public BigInteger divide(BigInteger val) {
         MutableBigInteger q = new MutableBigInteger(),
@@ -1352,7 +1352,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
      * @return an array of two BigIntegers: the quotient {@code (this / val)}
      *         is the initial element, and the remainder {@code (this % val)}
      *         is the final element.
-     * @throws ArithmeticException {@code val==0}
+     * @throws ArithmeticException if {@code val} is zero.
      */
     public BigInteger[] divideAndRemainder(BigInteger val) {
         BigInteger[] result = new BigInteger[2];
@@ -1371,7 +1371,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
      * @param  val value by which this BigInteger is to be divided, and the
      *         remainder computed.
      * @return {@code this % val}
-     * @throws ArithmeticException {@code val==0}
+     * @throws ArithmeticException if {@code val} is zero.
      */
     public BigInteger remainder(BigInteger val) {
         MutableBigInteger q = new MutableBigInteger(),
@@ -1547,7 +1547,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
      *
      * @param  m the modulus.
      * @return {@code this mod m}
-     * @throws ArithmeticException {@code m <= 0}
+     * @throws ArithmeticException {@code m} &le; 0
      * @see    #remainder
      */
     public BigInteger mod(BigInteger m) {
@@ -1566,7 +1566,9 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
      * @param  exponent the exponent.
      * @param  m the modulus.
      * @return <tt>this<sup>exponent</sup> mod m</tt>
-     * @throws ArithmeticException {@code m <= 0}
+     * @throws ArithmeticException {@code m} &le; 0 or the exponent is
+     *         negative and this BigInteger is not <i>relatively
+     *         prime</i> to {@code m}.
      * @see    #modInverse
      */
     public BigInteger modPow(BigInteger exponent, BigInteger m) {
@@ -2015,7 +2017,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
      *
      * @param  m the modulus.
      * @return {@code this}<sup>-1</sup> {@code mod m}.
-     * @throws ArithmeticException {@code  m <= 0}, or this BigInteger
+     * @throws ArithmeticException {@code  m} &le; 0, or this BigInteger
      *         has no multiplicative inverse mod m (that is, this BigInteger
      *         is not <i>relatively prime</i> to m).
      */
@@ -2449,7 +2451,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
     /**
      * Returns {@code true} if this BigInteger is probably prime,
      * {@code false} if it's definitely composite.  If
-     * {@code certainty} is {@code  <= 0}, {@code true} is
+     * {@code certainty} is &le; 0, {@code true} is
      * returned.
      *
      * @param  certainty a measure of the uncertainty that the caller is