e03 - Handout A -

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

Handout A, p. 2

class `java.util.ArrayList<E>`

The following excerpts from the javadoc for java.util.ArrayList<E> may be helpful to you in completing this exam.

Inheritance Hierarchy (complete)

java.lang.Object
  java.util.AbstractCollection<E>
    java.util.AbstractList<E>
      java.util.ArrayList<E>

All Implemented Interfaces:	`Serializable, Cloneable, Iterable<E>, Collection<E>, List<E>, RandomAccess`
Direct Known Subclasses:	`AttributeList, RoleList, RoleUnresolvedList`

Constructors (complete)

`ArrayList()`	Constructs an empty list with an initial capacity of ten.
`ArrayList(Collection<? extends E> c)`	Constructs a list containing the elements of the specified collection, in the order they are returned by the collection’s iterator.
`ArrayList(int initialCapacity)`	Constructs an empty list with the specified initial capacity.

Most important methods, with brief description

`boolean`	`add(E e)`	Appends the specified element to the end of this list.
`void`	`add(int index, E element)`	Inserts the specified element at the specified position in this list. Shifts the element currently at that position (if any) and any subsequent elements to the right (adds one to their indices). throws `IndexOutOfBoundsException` if `(index < 0 \|\| index > size())`
`void`	`clear()`	Removes all of the elements from this list.
`E`	`get(int index)`	Returns the element at the specified position in this list.
`int`	`indexOf(Object o)`	Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
`boolean`	`isEmpty()`	Returns true if this list contains no elements.
`int`	`lastIndexOf(Object o)`	Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
`E`	`remove(int index)`	Removes the element at the specified position in this list.
`boolean`	`remove(Object o)`	Removes the first occurrence of the specified element from this list, if it is present.
`E`	`set(int index, E element)`	Replaces the element at the specified position in this list with the specified element. Returns the element previously at the specified position throws `IndexOutOfBoundsException` if `(index < 0 \|\| index >= size())`
`int`	`size()`	Returns the number of elements in this list.
`void`	`sort(Comparator<? super E> c)`	Sorts this list according to the order induced by the specified `Comparator`.

Additional methods, listed by method signature only.

`boolean addAll(Collection<? extends E> c)`	`boolean addAll(int index, Collection<? extends E> c)`
`Object clone()`	`boolean contains(Object o)`
`void ensureCapacity(int minCapacity)`	`void forEach(Consumer<? super E> action)`
`Iterator<E> iterator()`	`ListIterator<E> listIterator()`
`ListIterator<E> listIterator(int index)`	`boolean removeAll(Collection<?> c)`
`boolean removeIf(Predicate<? super E> filter)`	`protected void removeRange(int fromIndex, int toIndex)`
`void replaceAll(UnaryOperator<E> operator)`	`boolean retainAll(Collection<?> c)`
`Spliterator<E> spliterator()`	`List<E> subList(int fromIndex, int toIndex)`
`Object[] toArray()`	`<T> T[] toArray(T[] a)`
`void trimToSize()`

Methods inherited from:

`class java.util.AbstractList`	`equals, hashCode`
`class java.util.AbstractCollection`	`containsAll, toString`
`class java.lang.Object`	`finalize, getClass, notify, notifyAll, wait, wait, wait`
`interface java.util.List`	`containsAll, equals, hashCode`
`interface java.util.Collection`	`parallelStream, stream`

End of Handout