e02 - Handout A -

Handout A, p. 1: Useful Reference Items

You may find it useful to know that the code String.format("%.2f", gpa) will format a double variable gpa with exactly two places after the decimal point.

In addition, 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.lang.Math has the following method for converting the double values into -1.0, 0.0 and 1.0 based on their sign. Type casting could be used to convert the returned double value to an int value.

static double signum(double d) Returns the signum function of the argument;
zero if the argument is zero,
1.0 if the argument is greater than zero,
-1.0 if the argument is less than zero.

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

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

And finally, java.lang.String implements Comparable<String> in the way that you would expect.

Handout A, p. 2: Sample Output

$ java StudentMain
Student(6234567,"Bob",3.25,CMPSC)
Student(7152353,"Charlie",3.96,CMPSC)
Student(2352353,"Alice",3.97,CMPEN)
Student(2888888,"Danielle",4.00,CMPSC)
Student(1152353,"Ed",2.90,CMPEN)
$ java StudentMain name
Student(2352353,"Alice",3.97,CMPEN)
Student(6234567,"Bob",3.25,CMPSC)
Student(7152353,"Charlie",3.96,CMPSC)
Student(2888888,"Danielle",4.00,CMPSC)
Student(1152353,"Ed",2.90,CMPEN)
$ java StudentMain majorName
Student(2352353,"Alice",3.97,CMPEN)
Student(1152353,"Ed",2.90,CMPEN)
Student(6234567,"Bob",3.25,CMPSC)
Student(7152353,"Charlie",3.96,CMPSC)
Student(2888888,"Danielle",4.00,CMPSC)
$ java StudentMain gpaDesc
Student(2888888,"Danielle",4.00,CMPSC)
Student(2352353,"Alice",3.97,CMPEN)
Student(7152353,"Charlie",3.96,CMPSC)
Student(6234567,"Bob",3.25,CMPSC)
Student(1152353,"Ed",2.90,CMPEN)
$ java StudentMain perm
Student(1152353,"Ed",2.90,CMPEN)
Student(2352353,"Alice",3.97,CMPEN)
Student(2888888,"Danielle",4.00,CMPSC)
Student(6234567,"Bob",3.25,CMPSC)
Student(7152353,"Charlie",3.96,CMPSC)
$

End of Handout