org.limewire.collection
Class FixedSizeSortedSet<E>

java.lang.Object
  org.limewire.collection.FixedSizeSortedSet<E>

All Implemented Interfaces:

Iterable<E>

public class FixedSizeSortedSet<E>
extends Object
implements Iterable<E>

Gives a sorted Set of elements with a maximum size. Elements are sorted upon insertion to the list, but only a fixed number of unique items are kept. Therefore, a newly inserted element can push out items depending on its insertion location. All inserted elements must implement the Comparable interface. Additionally, FixedSizeSortedSet does not accept duplicate elements.

hashCode() and equals(Object) are used to determine if an existing item needs to be replaced, but compareTo is used to determine which items are ejected. compareTo CAN be different from hashCode and equals (which is explicitly against the strong suggestion of compareTo and equals, but is necessary for FixedSizeSortedSet to function).

Note: FixedSizeSortedSet can use a class that has a natural ordering that is inconsistent with equals.

FixedSizeSortedSet is not thread-safe.

    //Consistent with equals
    public class MyPersonName implements Comparable {
        private int age ;
        private String name;

        MyPersonName(String name, int age){
            this.name = name;
            this.age = age;
        }

        public int age(){
            return age;
        }

        public String name(){
            return name;
        }

        public int compareTo(Object o){
            MyPersonName p = (MyPersonName) o;
            return this.name.compareTo(p.name());
        }

        public boolean equals(Object o){
            MyPersonName p = (MyPersonName) o;
            return name.equals(p.name());
        }

        public int hashCode(){
            return 37*name.hashCode();
        }

        public String toString(){
            return name + "'s age: " + age;
        }
    }

    //Note: This class has a natural ordering that is inconsistent with equals
    public class MyPersonAge implements Comparable {
        private int age ;
        private String name;

        MyPersonAge(String name, int age){
            this.name = name;
            this.age = age;
        }
        public int age(){
            return age;
        }
        public String name(){
            return name;
        }

        public int compareTo(Object o){
            MyPersonAge p = (MyPersonAge) o;
            return this.age - p.age() ;
        }

        public boolean equals(Object o){
            MyPersonAge p = (MyPersonAge) o;
            return name.equals(p.name());
        }

        public int hashCode(){
            return 37*name.hashCode();
        }

        public String toString(){
            return name + "'s age: " + age;
        }
    }

    void sampleCodeFixedSizeSortedSet(){

        //compareTo by Age
        System.out.println("When max. size met, evict people by oldest person.");
        FixedSizeSortedSet<MyPersonAge> age = new FixedSizeSortedSet<MyPersonAge>(5);
        age.add(new MyPersonAge("Abby", 23));

        if(!age.add(new MyPersonAge("Abby", 27)))
            System.out.println("Abby already contained in the collection; 23 is replaced with 27");
        age.add(new MyPersonAge("Chris", 20));
        age.add(new MyPersonAge("Bob", 28));
        age.add(new MyPersonAge("Dan", 25));
        age.add(new MyPersonAge("Eric", 24));
        //max reached
        age.add(new MyPersonAge("Fred", 22));

        for(MyPersonAge o : age)
            System.out.println(o.toString());   

        System.out.println("");

        //compareTo by Name
        System.out.println("When max. size met, evict people by alphabetical name.");
        FixedSizeSortedSet<MyPersonName> name = new FixedSizeSortedSet<MyPersonName>(5);
        name.add(new MyPersonName("Abby", 23));

        if(!name.add(new MyPersonName("Abby", 27)))
            System.out.println("Abby already contained in the collection; 23 is replaced with 27");
        name.add(new MyPersonName("Chris", 20));
        name.add(new MyPersonName("Bob", 28));
        name.add(new MyPersonName("Dan", 25));
        name.add(new MyPersonName("Eric", 24));
        //max reached
        name.add(new MyPersonName("Fred", 22));

        for(MyPersonName o : name)
            System.out.println(o.toString());       
    }
    Output:
        When max. size met, evict people by oldest person.
        Abby already contained in the collection; 23 is replaced with 27
        Chris's age: 20
        Fred's age: 22
        Eric's age: 24
        Dan's age: 25
        Abby's age: 27

        When max. size met, evict people by alphabetical name.
        Abby already contained in the collection; 23 is replaced with 27
        Abby's age: 27
        Bob's age: 28
        Chris's age: 20
        Dan's age: 25
        Fred's age: 22
 

Constructor Summary

FixedSizeSortedSet()
Constructs a FixedSizeSortedSet with a maximum size of 50.

FixedSizeSortedSet(Comparator<? super E> c)
Constructs a FixedSizeSortedSet with the specified comparator for the SortedSet and a maximum size of 50.

FixedSizeSortedSet(Comparator<? super E> c, int maxSize)
Constructs a FixedSizeSortedSet with the specified comparator and maximum size.

FixedSizeSortedSet(int size)
Constructs a FixedSizeSortedSet with a specified maximum size.

Method Summary

boolean	add(E o) Adds the object to the set.
boolean	addAll(Collection<? extends E> c) Adds all the elements of the specified collection to this set.
void	clear() Clears this FixedSizeSortedSet.
Object	clone()
boolean	contains(Object o) Determines if this set contains the specified object.
boolean	equals(Object o)
E	first() Returns the first element in the sorted set.
E	get(E o) Retrieves the element that has an equals comparison with this object and is in this FixedSizeSortedSet.
int	hashCode()
boolean	isEmpty()
Iterator<E>	iterator()
E	last() Returns the last element in the sorted set.
boolean	remove(E o) Removes the specified object from this sorted set.
int	size()

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FixedSizeSortedSet

public FixedSizeSortedSet()

Constructs a FixedSizeSortedSet with a maximum size of 50.

FixedSizeSortedSet

public FixedSizeSortedSet(int size)

Constructs a FixedSizeSortedSet with a specified maximum size.

FixedSizeSortedSet

public FixedSizeSortedSet(Comparator<? super E> c)

Constructs a FixedSizeSortedSet with the specified comparator for the SortedSet and a maximum size of 50.

FixedSizeSortedSet

public FixedSizeSortedSet(Comparator<? super E> c,
                          int maxSize)

Constructs a FixedSizeSortedSet with the specified comparator and maximum size.

Method Detail

clone

public Object clone()
             throws CloneNotSupportedException

Overrides:

clone in class Object

Throws:

CloneNotSupportedException

add

public boolean add(E o)

Adds the object to the set. If the object is already present, (as specified by the Map's equals comparison), then it is ejected and this newer version is used.

addAll

public boolean addAll(Collection<? extends E> c)

Adds all the elements of the specified collection to this set.

get

public E get(E o)

Retrieves the element that has an equals comparison with this object and is in this FixedSizeSortedSet.

last

public E last()

Returns the last element in the sorted set.

first

public E first()

Returns the first element in the sorted set.

remove

public boolean remove(E o)

Removes the specified object from this sorted set. Equality is determined by equals, not compareTo.

clear

public void clear()

Clears this FixedSizeSortedSet.

contains

public boolean contains(Object o)

Determines if this set contains the specified object. Equality is determined by equals, not compareTo.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

isEmpty

public boolean isEmpty()

iterator

public Iterator<E> iterator()

Specified by:

iterator in interface Iterable<E>

size

public int size()