Primitives.java

import checkers.interning.quals.*;

import java.util.*;

public class Primitives {

    void test() {
        int a = 3;

        if (a == 3)
            System.out.println("yes");
        else
            System.out.println("no");

        if (a != 2)
            System.out.println("yes");
        else
            System.out.println("no");

        String name = "Interning";
        if ((name.indexOf('[') == -1) && (name.indexOf('(') == -1))
            System.out.println("has no open punctuation");
        else
            System.out.println("has open punctuation");

        Number n = new Integer(22);
        boolean is_double = (n instanceof Double); // valid

        int index = 0;
        index = Integer.decode ("22"); // valid: auto-unboxing conversion

        // auto-unboxing conversion again
        Map<String,Integer> m = new HashMap<String,Integer>();
        if (m.get("hello") == 22) {
            System.out.println("hello maps to 22");
        }

    }

  public static int pow_fast(int base, int expt) throws ArithmeticException {
    if (expt < 0)
      throw new ArithmeticException("Negative base passed to pow");

    int this_square_pow = base;
    int result = 1;
    while (expt>0) {
      if ((expt & 1) != 0)
        result *= this_square_pow;
      expt >>= 1;
      this_square_pow *= this_square_pow;
    }
    return result;
  }

  /** Return the greatest common divisor of the two arguments. */
  public static int gcd(int a, int b) {

    // Euclid's method
    if (b == 0)
      return (Math.abs(a));
    a = Math.abs(a);
    b = Math.abs(b);
    while (b != 0) {
      int tmp = b;
      b = a % b;
      a = tmp;
    }
    return a;
  }

  /** Return the greatest common divisor of the elements of int array a. */
  public static int gcd(int[] a) {
    // Euclid's method
    if (a.length == 0) {
      return 0;
    }
    int result = a[0];
    for (int i=1; i<a.length; i++) {
      result = gcd(a[i], result);
      if ((result == 1) || (result == 0))
        return result;
    }
    return result;
  }

  /**
   * Return the gcd (greatest common divisor) of the differences
   * between the elements of int array a.
   **/
  public static int gcd_differences(int[] a) {
    // Euclid's method
    if (a.length < 2) {
      return 0;
    }
    int result = a[1] - a[0];
    for (int i=2; i<a.length; i++) {
      result = gcd(a[i] - a[i-1], result);
      if ((result == 1) || (result == 0))
        return result;
    }
    return result;
  }


}