e01 - Handout B -

Useful Reference Items related to Sorting

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 its two arguments o1 and o2 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 interface java.lang.Comparable<T> includes the following method signature:

int compareTo(T o) Compares this object with the specified object o 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 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.Integer:

public static int compare(int i1, int i2) Compares the two specified int values.
The sign of the int value returned
matches the contract of the compare method in java.util.Comparator

End of Handout