SecureRandom

Returns a stream producing the given streamSize number of pseudorandom double values, each between zero (inclusive) and one (exclusive).

A pseudorandom double value is generated as if it's the result of calling the method nextDouble().

Returns an effectively unlimited stream of pseudorandom double values, each between zero (inclusive) and one (exclusive).

A pseudorandom double value is generated as if it's the result of calling the method nextDouble().

Returns a stream producing the given streamSize number of pseudorandom double values, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom double value is generated as if it's the result of calling the following method with the origin and bound:

<code>double nextDouble(double origin, double bound) {
    double r = nextDouble();
    r = r * (bound - origin) + origin;
    if (r &gt;= bound) // correct for rounding
      r = Math.nextDown(bound);
    return r;
  }</code>

Returns an effectively unlimited stream of pseudorandom double values, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom double value is generated as if it's the result of calling the following method with the origin and bound:

<code>double nextDouble(double origin, double bound) {
    double r = nextDouble();
    r = r * (bound - origin) + origin;
    if (r &gt;= bound) // correct for rounding
      r = Math.nextDown(bound);
    return r;
  }</code>

Returns a stream producing the given streamSize number of pseudorandom int values.

A pseudorandom int value is generated as if it's the result of calling the method nextInt().

Returns an effectively unlimited stream of pseudorandom int values.

A pseudorandom int value is generated as if it's the result of calling the method nextInt().

Returns a stream producing the given streamSize number of pseudorandom int values, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom int value is generated as if it's the result of calling the following method with the origin and bound:

<code>int nextInt(int origin, int bound) {
    int n = bound - origin;
    if (n &gt; 0) {
      return nextInt(n) + origin;
    }
    else {  // range not representable as int
      int r;
      do {
        r = nextInt();
      } while (r &lt; origin || r &gt;= bound);
      return r;
    }
  }</code>

Returns an effectively unlimited stream of pseudorandom int values, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom int value is generated as if it's the result of calling the following method with the origin and bound:

<code>int nextInt(int origin, int bound) {
    int n = bound - origin;
    if (n &gt; 0) {
      return nextInt(n) + origin;
    }
    else {  // range not representable as int
      int r;
      do {
        r = nextInt();
      } while (r &lt; origin || r &gt;= bound);
      return r;
    }
  }</code>

Returns a stream producing the given streamSize number of pseudorandom long values.

A pseudorandom long value is generated as if it's the result of calling the method nextLong().

Returns an effectively unlimited stream of pseudorandom long values.

A pseudorandom long value is generated as if it's the result of calling the method nextLong().

Returns a stream producing the given streamSize number of pseudorandom long, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom long value is generated as if it's the result of calling the following method with the origin and bound:

<code>long nextLong(long origin, long bound) {
    long r = nextLong();
    long n = bound - origin, m = n - 1;
    if ((n &amp; m) == 0L)  // power of two
      r = (r &amp; m) + origin;
    else if (n &gt; 0L) {  // reject over-represented candidates
      for (long u = r &gt;&gt;&gt; 1;            // ensure nonnegative
           u + m - (r = u % n) &lt; 0L;    // rejection check
           u = nextLong() &gt;&gt;&gt; 1) // retry
          ;
      r += origin;
    }
    else {              // range not representable as long
      while (r &lt; origin || r &gt;= bound)
        r = nextLong();
    }
    return r;
  }</code>

Returns an effectively unlimited stream of pseudorandom long values, each conforming to the given origin (inclusive) and bound (exclusive).

A pseudorandom long value is generated as if it's the result of calling the following method with the origin and bound:

<code>long nextLong(long origin, long bound) {
    long r = nextLong();
    long n = bound - origin, m = n - 1;
    if ((n &amp; m) == 0L)  // power of two
      r = (r &amp; m) + origin;
    else if (n &gt; 0L) {  // reject over-represented candidates
      for (long u = r &gt;&gt;&gt; 1;            // ensure nonnegative
           u + m - (r = u % n) &lt; 0L;    // rejection check
           u = nextLong() &gt;&gt;&gt; 1) // retry
          ;
      r += origin;
    }
    else {              // range not representable as long
      while (r &lt; origin || r &gt;= bound)
        r = nextLong();
    }
    return r;
  }</code>

Returns the next pseudorandom, uniformly distributed boolean value from this random number generator's sequence. The general contract of nextBoolean is that one boolean value is pseudorandomly generated and returned. The values true and false are produced with (approximately) equal probability.

The method nextBoolean is implemented by class Random as if by:

<code>public boolean nextBoolean() {
    return next(1) != 0;
  }</code>

Returns the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence.

The general contract of nextDouble is that one double value, chosen (approximately) uniformly from the range 0.0d (inclusive) to 1.0d (exclusive), is pseudorandomly generated and returned.

The method nextDouble is implemented by class Random as if by:

<code>public double nextDouble() {
    return (((long)next(26) &lt;&lt; 27) + next(27))
      / (double)(1L &lt;&lt; 53);
  }</code>

The hedge "approximately" is used in the foregoing description only because the next method is only approximately an unbiased source of independently chosen bits. If it were a perfect source of randomly chosen bits, then the algorithm shown would choose double values from the stated range with perfect uniformity.

[In early versions of Java, the result was incorrectly calculated as:

<code>return (((long)next(27) &lt;&lt; 27) + next(27))
      / (double)(1L &lt;&lt; 54);</code>

Returns the next pseudorandom, uniformly distributed float value between 0.0 and 1.0 from this random number generator's sequence.

The general contract of nextFloat is that one float value, chosen (approximately) uniformly from the range 0.0f (inclusive) to 1.0f (exclusive), is pseudorandomly generated and returned. All 224 possible float values of the form m x 2-24, where m is a positive integer less than 224, are produced with (approximately) equal probability.

The method nextFloat is implemented by class Random as if by:

<code>public float nextFloat() {
    return next(24) / ((float)(1 &lt;&lt; 24));
  }</code>

The hedge "approximately" is used in the foregoing description only because the next method is only approximately an unbiased source of independently chosen bits. If it were a perfect source of randomly chosen bits, then the algorithm shown would choose float values from the stated range with perfect uniformity.

[In early versions of Java, the result was incorrectly calculated as:

<code>return next(30) / ((float)(1 &lt;&lt; 30));</code>

Returns the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence.

The general contract of nextGaussian is that one double value, chosen from (approximately) the usual normal distribution with mean 0.0 and standard deviation 1.0, is pseudorandomly generated and returned.

The method nextGaussian is implemented by class Random as if by a threadsafe version of the following:

<code>private double nextNextGaussian;
  private boolean haveNextNextGaussian = false;
 
  public double nextGaussian() {
    if (haveNextNextGaussian) {
      haveNextNextGaussian = false;
      return nextNextGaussian;
    } else {
      double v1, v2, s;
      do {
        v1 = 2 * nextDouble() - 1;   // between -1.0 and 1.0
        v2 = 2 * nextDouble() - 1;   // between -1.0 and 1.0
        s = v1 * v1 + v2 * v2;
      } while (s &gt;= 1 || s == 0);
      double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
      nextNextGaussian = v2 * multiplier;
      haveNextNextGaussian = true;
      return v1 * multiplier;
    }
  }</code>

Returns the next pseudorandom, uniformly distributed int value from this random number generator's sequence. The general contract of nextInt is that one int value is pseudorandomly generated and returned. All 232 possible int values are produced with (approximately) equal probability.

The method nextInt is implemented by class Random as if by:

<code>public int nextInt() {
    return next(32);
  }</code>

Returns a pseudorandom, uniformly distributed int value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence. The general contract of nextInt is that one int value in the specified range is pseudorandomly generated and returned. All bound possible int values are produced with (approximately) equal probability. The method nextInt(int bound) is implemented by class Random as if by:

<code>public int nextInt(int bound) {
    if (bound &lt;= 0)
      throw new IllegalArgumentException("bound must be positive");
 
    if ((bound &amp; -bound) == bound)  // i.e., bound is a power of 2
      return (int)((bound * (long)next(31)) &gt;&gt; 31);
 
    int bits, val;
    do {
        bits = next(31);
        val = bits % bound;
    } while (bits - val + (bound-1) &lt; 0);
    return val;
  }</code>

The hedge "approximately" is used in the foregoing description only because the next method is only approximately an unbiased source of independently chosen bits. If it were a perfect source of randomly chosen bits, then the algorithm shown would choose int values from the stated range with perfect uniformity.

The algorithm is slightly tricky. It rejects values that would result in an uneven distribution (due to the fact that 2^31 is not divisible by n). The probability of a value being rejected depends on n. The worst case is n=2^30+1, for which the probability of a reject is 1/2, and the expected number of iterations before the loop terminates is 2.

The algorithm treats the case where n is a power of two specially: it returns the correct number of high-order bits from the underlying pseudo-random number generator. In the absence of special treatment, the correct number of low-order bits would be returned. Linear congruential pseudo-random number generators such as the one implemented by this class are known to have short periods in the sequence of values of their low-order bits. Thus, this special case greatly increases the length of the sequence of values returned by successive calls to this method if n is a small power of two.

Returns the next pseudorandom, uniformly distributed value from this random number generator's sequence. The general contract of nextLong is that one value is pseudorandomly generated and returned.

The method nextLong is implemented by class Random as if by:

<code>public long nextLong() {
    return ((long)next(32) &lt;&lt; 32) + next(32);
  }</code>