Handout B, p. 1: Useful Reference Items

Here are a few reminders of things we discussed in class, but that you might reasonably need a “reference” for if you were using them in the real world.

The interface java.util.Comparator<T> includes the following method signature:

int compare(T o1, T o2) Compares this object with the specified object for order.
Returns a negative integer, zero, or a positive integer
as this object is less than, equal to, or greater than the specified object.

The interface java.lang.Comparable<T> includes the following method signature:

int compareTo(T o) Compares its two arguments for order.
Returns a negative integer, zero, or a positive integer
as the first argument is less than, equal to, or greater than the second.

The class java.util.ArrayList<E> includes this method:

void sort(Comparator<? super E> c) Sorts this list according to the order induced by the specified Comparator.

The class java.util.Collections contains the following static method:

static <T extends Comparable<? super T>> void sort(List<T> list) Sorts the specified list into ascending order,
according to the natural ordering of its elements.

The classes java.lang.String and java.lang.Double implement Comparable<String> and Comparable<Double>, each in the way that you would expect.

Other potentially useful methods

In java.lang.Double:

public static int compare(double d1, double d2) Compares the two specified double values.
The sign of the integer value returned
is the same as that of the integer that
would be returned by the call:
new Double(d1).compareTo(new Double(d2))

End of Handout