Java Collection Framework

Contains all Interfaces and Classes, Example programs with output

1. The Collection Framework
By,
Lakshmi R
Asst. Professor
Dept. of ISE

2. Collection –Group of objects
Collection Framework –
•Classes and Interfaces that manage collections.
•Provides an architecture to store and manipulate the group of objects.
•Standardizes the way in which group of objects that are handled by
your programs.
Overview
30-12-2017 2Lakshmi R, Asst. Professor, Dept. of ISE

3. 30-12-2017 3Lakshmi R, Asst. Professor, Dept. of ISE

4. •Performance-efficient implementation of data structures like lists, array lists,
trees, set, hash tables and many more. (You don’t have to code manually)
•Interoperability –different types of collections wok in similar manner
•Easy–Extension and Adaption. Collections Framework is built upon a set of
standard interfaces
•Integrationof standard arrays to Collection Framework.
•Algorithms–Defined as static methods within the Collectionclass
•Iteratorinterface –Standard way of accessing the elements within a collection.
•Each collection implements Iterator. Eg: Code that cycles through a set can be used to cycle
through a list.
Design Goal
30-12-2017 4Lakshmi R, Asst. Professor, Dept. of ISE

5. The Collection Interfaces
30-12-2017 5Lakshmi R, Asst. Professor, Dept. of ISE

6. The Collection Interface
•It is a generic interface.
Declaration:
interface Collection<E>
•Where E represents the type of objects the collection can
hold.
•Collection extends the Iterableinterface. (Hence, it can be
cycled through for-each version of for loop)
30-12-2017 6Lakshmi R, Asst. Professor, Dept. of ISE

7. 30-12-2017 7Lakshmi R, Asst. Professor, Dept. of ISE

8. 30-12-2017 8Lakshmi R, Asst. Professor, Dept. of ISE

9. The List Interface
•It is a generic interface.
•List extends Collection interface.
Declaration:
interface List<E>
•Where E represents the type of objects the list can hold.
•List may contain duplicate elements.
30-12-2017 9Lakshmi R, Asst. Professor, Dept. of ISE

10. 30-12-2017 10Lakshmi R, Asst. Professor, Dept. of ISE

11. The Set Interface
•It is a generic interface.
•Set extends Collection interface.
Declaration:
interface Set<E>
•Where E represents the type of objects the set can hold.
•Set doesn’t contain duplicate elements.
•No methods of its own.
30-12-2017 11Lakshmi R, Asst. Professor, Dept. of ISE

12. The SortedSetInterface
•It is a generic interface.
•Set extends Set interface.
Declaration:
interface SortedSet<E>
•Where E represents the type of objects the SortedSetcan hold.
•Set doesn’t contain duplicate elements.
•Declares set in ascending order.
30-12-2017 12Lakshmi R, Asst. Professor, Dept. of ISE

13. 30-12-2017 13Lakshmi R, Asst. Professor, Dept. of ISE

14. The Queue Interface
•Queue is a generic interface
•The Queue interface extends Collection
•It declares the behavior of a queue (first-in, first-out list)
Declaration:
interface Queue<E>
30-12-2017 14Lakshmi R, Asst. Professor, Dept. of ISE

15. 30-12-2017 15Lakshmi R, Asst. Professor, Dept. of ISE

16. The DequeInterface
•It extends Queue and declares the behavior of a double-ended queue
•Double-ended queues can function as standard, first-in, first-out
queues or as last-in, first-out stacks.
Declaration:
interface Deque<E>
30-12-2017 16Lakshmi R, Asst. Professor, Dept. of ISE

17. 30-12-2017 17Lakshmi R, Asst. Professor, Dept. of ISE

18. 30-12-2017 18Lakshmi R, Asst. Professor, Dept. of ISE

19. The Collection Classes
30-12-2017 19Lakshmi R, Asst. Professor, Dept. of ISE

20. The ArrayListClass
•The ArrayListclass extends AbstractListand implements the List
interface
Declaration:
Class ArrayList<E>
Constructors:
ArrayList( ) –Empty array list
ArrayList(Collection<? extends E> c)
ArrayList(intcapacity)
30-12-2017 20Lakshmi R, Asst. Professor, Dept. of ISE

21. // Demonstrate ArrayList.
import java.util.*;
class ArrayListDemo{
public static void main(String args[]) {
// Create an array list.
ArrayList<String> al = new ArrayList<String>();
System.out.println("Initial size of al: " + al.size());
// Add elements to the array list.
al.add("C");
al.add("A");
al.add("E");
al.add("B");
al.add("D");
al.add("F");
30-12-2017 21Lakshmi R, Asst. Professor, Dept. of ISE

22. al.add(1, "A2");
System.out.println("Size of al after additions: " + al.size());
// Display the array list.
System.out.println("Contents of al: " + al);
// Remove elements from the array list.
al.remove("F");
al.remove(2);
System.out.println("Size of al after deletions: " +al.size());
System.out.println("Contents of al: " + al); } }
The output from this program is shown here:
Initial size of al: 0
Size of al after additions: 7
Contents of al: [C, A2, A, E, B, D, F]
Size of al after deletions: 5
Contents of al: [C, A2, E, B, D]
30-12-2017 22Lakshmi R, Asst. Professor, Dept. of ISE

23. Obtaining an Array from an ArrayList
// Convert an ArrayListinto an array.
import java.util.*;
class ArrayListToArray{
public static void main(String args[]) {
// Create an array list.
ArrayList<Integer> al = new ArrayList<Integer>();
// Add elements to the array list.
al.add(1);
al.add(2);
al.add(3);
al.add(4);
30-12-2017 23Lakshmi R, Asst. Professor, Dept. of ISE

24. System.out.println("Contents of al: " + al);
// Get the array.
Integer ia[] = new Integer[al.size()];
ia= al.toArray(ia);
intsum = 0;
// Sum the array.
for(int i : ia) sum += i;
System.out.println("Sum is: " + sum);
}
}
The output from the program is shown here:
Contents of al: [1, 2, 3, 4]
Sum is: 10
30-12-2017 24Lakshmi R, Asst. Professor, Dept. of ISE

25. The LinkedListClass
•The LinkedListclass extends AbstractSequentialList
•Implements the List, Deque, and Queue interfaces
•LinkedListis a generic class
Declaration:
Class LinkedList<E>
Constructors:
LinkedList( ) –Empty linked list
LinkedList(Collection<? extends E> c)
30-12-2017 25Lakshmi R, Asst. Professor, Dept. of ISE

26. // Demonstrate LinkedList.
import java.util.*;
class LinkedListDemo{
public static void main(String args[]) {
// Create a linked list.
LinkedList<String> ll= new LinkedList<String>();
// Add elements to the linked list.
ll.add("F");
ll.add("B");
ll.add("D");
ll.add("E");
ll.add("C");
ll.addLast("Z");
ll.addFirst("A");
ll.add(1, "A2");
30-12-2017 26Lakshmi R, Asst. Professor, Dept. of ISE

27. // Remove elements from the linked list.
ll.remove("F");
ll.remove(2);
System.out.println("Contents of llafter deletion: "+ ll);
// Remove first and last elements.
ll.removeFirst();
ll.removeLast();
System.out.println("llafter deleting first and last: "+ ll);
// Get and set a value .
String val= ll.get(2);
ll.set(2, val+ " Changed");
System.out.println("llafter change: " + ll);
}
}
30-12-2017 27Lakshmi R, Asst. Professor, Dept. of ISE

28. The output from this program is shown here:
Original contents of ll: [A, A2, F, B, D, E, C, Z]
Contents of llafter deletion: [A, A 2, D, E, C, Z]
llafter deleting first and last: [A 2, D, E, C]
llafter change: [A2, D, E Changed, C]
30-12-2017 28Lakshmi R, Asst. Professor, Dept. of ISE

29. The HashSetClass
•HashSetextends AbstractSetand implements the Set interface
Declaration
class HashSet<E>
Constructors
HashSet( ) –Default size 16
HashSet(Collection<? extends E> c)
HashSet(intcapacity)
HashSet(intcapacity, float fillRatio)
30-12-2017 29Lakshmi R, Asst. Professor, Dept. of ISE

30. // Demonstrate HashSet.
import java.util.*;
class HashSetDemo{
public static void main(String args[]) {
// Create a hash set.
HashSet<String> hs= new HashSet<String>();
// Add elements to the hash set.
hs.add("B");
hs.add("A");
hs.add("D");
hs.add("E");
hs.add("C");
hs.add("F");
System.out.println(hs);
}
}
The following is the output from this program:
[D, A, F, C, B, E]
30-12-2017 30Lakshmi R, Asst. Professor, Dept. of ISE

31. The LinkedHashSetClass
•The LinkedHashSetclass extends HashSet
Declaration
class LinkedHashSet<E>
•Uses linked list to store hash set.
30-12-2017 31Lakshmi R, Asst. Professor, Dept. of ISE

32. The TreeSetClass
Declaration:
class TreeSet<E>
TreeSet( )
TreeSet(Collection<? extends E> c)
TreeSet(Comparator<? super E> comp)
TreeSet(SortedSet<E> ss)
30-12-2017 32Lakshmi R, Asst. Professor, Dept. of ISE

33. // Demonstrate TreeSet.
import java.util.*;
class TreeSetDemo{
public static void main(String args[]) {
// Create a tree set.
TreeSet<String> ts= new TreeSet<String>();
// Add elements to the tree set.
ts.add("C");
ts.add("A");
ts.add("B");
ts.add("E");
ts.add("F");
ts.add("D");
System.out.println(ts);
}
}
The output from this program is shown here:
[A, B, C, D, E, F]
30-12-2017 33Lakshmi R, Asst. Professor, Dept. of ISE

34. The PriorityQueueClass
•PriorityQueueextends AbstractQueueand implements the Queue
interface
Declaration
class PriorityQueue<E>
Constructors
PriorityQueue( ) –Starting Capacity is 11
PriorityQueue(intcapacity)
PriorityQueue(intcapacity, Comparator<? super E> comp)
PriorityQueue(Collection<? extends E> c)
PriorityQueue(PriorityQueue<? extends E> c)
PriorityQueue(SortedSet<? extends E> c)
30-12-2017 34Lakshmi R, Asst. Professor, Dept. of ISE

35. The ArrayDequeClass
•It extends AbstractCollectionand implements the Dequeinterface
Declaration
class ArrayDeque<E>
Constuctors:
ArrayDeque( ) –Starting Capacity 16
ArrayDeque(intsize)
ArrayDeque(Collection<? extends E> c)
30-12-2017 35Lakshmi R, Asst. Professor, Dept. of ISE

36. Accessing a Collection via an Iterator
interface Iterator<E> -Single Directional Traversal
interface ListIterator<E> -Bidirectional Traversal
30-12-2017 36Lakshmi R, Asst. Professor, Dept. of ISE

37. 30-12-2017 37Lakshmi R, Asst. Professor, Dept. of ISE

38. // Demonstrate iterators.
import java.util.*;
class IteratorDemo{
public static void main(String args[]) {
// Create an array list.
ArrayList<String> al = new ArrayList<String>();
// Add elements to the array list.
al.add("C");
al.add("A");
al.add("E");
al.add("B");
al.add("D");
al.add("F");
30-12-2017 38Lakshmi R, Asst. Professor, Dept. of ISE

39. // Use iterator to display contents of al.
System.out.print("Original contents of al: ");
Iterator<String> itr= al.iterator();
while(itr.hasNext()) {
String element = itr.next();
System.out.print(element + " ");
}
System.out.println();
// Modify objects being iterated.
ListIterator<String> litr= al.listIterator();
while(litr.hasNext()) {
String element = litr.next();
litr.set(element + "+");
}
30-12-2017 39Lakshmi R, Asst. Professor, Dept. of ISE

40. System.out.print("Modified contents of al: ");
itr= al.iterator();
while(itr.hasNext()) {
String element = itr.next();
System.out.print(element + " ");
}
System.out.println();
// Now, display the list backwards.
System.out.print("Modified list backwards: ");
while(litr.hasPrevious()) {
String element = litr.previous();
System.out.print(element + " ");
}
System.out.println();
}
}
The output is shown here:
Original contents of al: C A E B D F
Modified contents of al: C+ A+ E+ B+ D+ F+
Modified list backwards: F+ D+ B+ E+ A+ C+
30-12-2017 40Lakshmi R, Asst. Professor, Dept. of ISE

41. The For-Each Alternative to Iterators
// Use the for-each for loop to cycle through a collection.
import java.util.*;
class ForEachDemo{
public static void main(String args[]) {
// Create an array list for integers.
ArrayList<Integer> vals= new ArrayList<Integer>();
// Add values to the array list.
vals.add(1);
vals.add(2);
vals.add(3);
vals.add(4);
vals.add(5);
30-12-2017 41Lakshmi R, Asst. Professor, Dept. of ISE

42. // Use for loop to display the values.
System.out.print("Original contents of vals: ");
for(intv : vals)
System.out.print(v + " ");
System.out.println();
// Now, sum the values by using a for loop.
intsum = 0;
for(intv : vals)
sum += v;
System.out.println("Sum of values: " + sum);
}
}
The output from the program is shown here:
Original contents of vals: 1 2 3 4 5
Sum of values: 15
30-12-2017 42Lakshmi R, Asst. Professor, Dept. of ISE

43. Storing User-Defined Classes in Collections
// A simple mailing list example.
import java.util.*;
class Address {
private String name;
private String street;
private String city;
private String state;
private String code;
Address(String n, String s, String c,
String st, String cd) {
name = n;
street = s;
city = c;
state = st;
code = cd;
}
public String toString() {
return name + "\n" + street + "\n" +
city + " " + state + " " + code; } }
30-12-2017 43Lakshmi R, Asst. Professor, Dept. of ISE

44. class MailList{
public static void main(String args[]) {
LinkedList<Address> ml = new LinkedList<Address>();
// Add elements to the linked list.
ml.add(new Address("J.W. West", " 11 Oak Ave","Urbana", "IL", "61801"));
ml.add(new Address("Ralph Baker", " 1142 Maple Lane","Mahomet", "IL",
"61853"));
ml.add(new Address("Tom Carlton", " 867 Elm St","Champaign", "IL",61820"));
// Display the mailing list.
for(Address element : ml)
System.out.println(element + "\n");
System.out.println();
}
}
30-12-2017 44Lakshmi R, Asst. Professor, Dept. of ISE

45. Working with Maps
•A map is an object that stores associations between keys and values,
or key/value pairs.
•Given a key, you can find its value. Both keys and values are objects.
•The keys must be unique, but the values may be duplicated.
30-12-2017 45Lakshmi R, Asst. Professor, Dept. of ISE

46. The Map Interface
•The Map interface maps unique keys to values. A key is an object that
you use to retrieve a value at a later date.
•Given a key and a value, you can store the value in a Map object.
•After the value is stored, you can retrieve it by using its key.
Declaration:
interface Map<K, V>
30-12-2017 46Lakshmi R, Asst. Professor, Dept. of ISE

47. 30-12-2017 47Lakshmi R, Asst. Professor, Dept. of ISE

48. The SortedMapInterface
•The SortedMapinterface extends Map.
•It ensures that the entries are maintained in ascending order based
on the keys.
•SortedMapis generic
Declaration
interface SortedMap<K, V>
30-12-2017 48Lakshmi R, Asst. Professor, Dept. of ISE

49. 30-12-2017 49Lakshmi R, Asst. Professor, Dept. of ISE

50. The Map.EntryInterface
•The Map.Entryinterface enables you to work with a map entry.
30-12-2017 50Lakshmi R, Asst. Professor, Dept. of ISE

51. The Map Classes
The HashMapClass
HashMapis a generic class that has this declaration:
class HashMap<K, V>
Constructors:
HashMap( )
HashMap(Map<? extends K, ? extends V> m)
HashMap(intcapacity)
HashMap(intcapacity, float fillRatio)
30-12-2017 51Lakshmi R, Asst. Professor, Dept. of ISE

52. import java.util.*;
class HashMapDemo{
public static void main(String args[]) {
// Create a hash map.
HashMap<String, Double> hm= new HashMap<String, Double>();
// Put elements to the map
hm.put("John Doe", new Double( 3434.34));
hm.put("Tom Smith", new Double( 123.22));
hm.put("Jane Baker", new Double( 1378.00));
hm.put("Tod Hall", new Double( 99.22));
hm.put("Ralph Smith", new Double( -19.08));
30-12-2017 52Lakshmi R, Asst. Professor, Dept. of ISE

53. // Get a set of the entries.
Set<Map.Entry<String, Double>> set = hm.entrySet();
// Display the set.
for(Map.Entry<String, Double> me : set) {
System.out.print(me.getKey() + ": ");
System.out.println(me.getValue());
}
System.out.println();
// Deposit 1000 into John Doe's account.
double balance = hm.get("John Doe");
hm.put("John Doe", balance + 1000);
System.out.println("John Doe's new balance: " +
hm.get("John Doe"));
}
}
30-12-2017 53Lakshmi R, Asst. Professor, Dept. of ISE

54. The TreeMapClass
Declaration:
class TreeMap<K, V>
Constructors:
TreeMap( )
TreeMap(Comparator<? super K> comp)
TreeMap(Map<? extends K, ? extends V> m)
TreeMap(SortedMap<K, ? extends V> sm)
30-12-2017 54Lakshmi R, Asst. Professor, Dept. of ISE

55. import java.util.*;
class TreeMapDemo{
public static void main(String args[]) {
// Create a tree map.
TreeMap<String, Double> tm = new TreeMap<String, Double>();
// Put elements to the map.
tm.put("John Doe", new Double( 3434.34));
tm.put("Tom Smith", new Double( 123.22));
tm.put("Jane Baker", new Double( 1378.00));
tm.put("Tod Hall", new Double( 99.22));
tm.put("Ralph Smith", new Double( -19.08));
30-12-2017 55Lakshmi R, Asst. Professor, Dept. of ISE

56. // Get a set of the entries.
Set<Map.Entry<String, Double>> set = tm.entrySet();
// Display the elements.
for(Map.Entry<String, Double> me : set) {
System.out.print(me.getKey() + ": ");
System.out.println(me.getValue());
}
System.out.println();
// Deposit 1000 into John Doe's account.
double balance = tm.get("John Doe");
tm.put("John Doe", balance + 1000);
System.out.println("John Doe's new balance: " +
tm.get("John Doe"));
}
}
30-12-2017 56Lakshmi R, Asst. Professor, Dept. of ISE

57. Using Comparator
•Java Comparator interfaceis used to order the objects of user-
defined class.
•A comparator object is capable of comparing two objects of two
different classes
Methods:
intcompare(T obj1, T obj2)
booleanequals(Object obj)
30-12-2017 57Lakshmi R, Asst. Professor, Dept. of ISE

58. // Use a custom comparator.
import java.util.*;
// A reverse comparator for strings.
class MyCompimplements Comparator<String> {
public intcompare(String a, String b) {
String aStr, bStr;
aStr= a;
bStr= b;
// Reverse the comparison.
return bStr.compareTo(aStr);
}
// No need to override equals.
}
30-12-2017 58Lakshmi R, Asst. Professor, Dept. of ISE

59. class CompDemo{
public static void main(String args[]) {
// Create a tree set.
TreeSet<String> ts= new TreeSet<String>(new
MyComp());
// Add elements to the tree set.
ts.add("C");
ts.add("A");
ts.add("B");
ts.add("E");
ts.add("F");
ts.add("D");
// Display the elements.
for(String element : ts)
System.out.print(element + " ");
System.out.println(); } }
As the following output shows, the tree
is now stored in reverse order:
F E D C B A
30-12-2017 59Lakshmi R, Asst. Professor, Dept. of ISE

60. class Arrays
•It provides various methods that are useful when working with arrays
•These methods help bridge the gap between collections and arrays
asList( ) method –it returns List view of an array
static <T> List asList(T ... array)
Here, array is the array that contains the data.
30-12-2017 60Lakshmi R, Asst. Professor, Dept. of ISE

61. Methods defined in Arrays
•The binarySearch( ) method
•The copyOf() method
•The copyOfRange( ) method
•The equals( ) method
•The fill( ) method
•The sort( ) method
30-12-2017 61Lakshmi R, Asst. Professor, Dept. of ISE

62. The binarySearch( ) method –various forms
•On successful search, it returns position of the key element in specified
array. Otherwise returns negative value.
static intbinarySearch(byte array[ ], byte value)
static intbinarySearch(char array[ ], char value)
static intbinarySearch(double array[ ], double value)
static intbinarySearch(float array[ ], float value)
static intbinarySearch(intarray[ ], intvalue)
static intbinarySearch(long array[ ], long value)
static intbinarySearch(short array[ ], short value)
static intbinarySearch(Object array[ ], Object value)
static <T> intbinarySearch(T[ ] array, T value, Comparator<? super T> c)
30-12-2017 62Lakshmi R, Asst. Professor, Dept. of ISE

63. The copyOf() method –various forms
•It returns a copy of an array.
•The original array is specified by source and the length of the copy is
specified by len.
•If the copy is longer than source, then
•the copy is padded with zeroes for numeric arrays
•nulls for object arrays
•false for booleanarrays
•If the copy is shorter than source, then the copy is truncated
Various forms:
static boolean[ ] copyOf(boolean[ ] source, intlen)
static byte[ ] copyOf(byte[ ] source, intlen)
static char[ ] copyOf(char[ ] source, intlen)
30-12-2017 63Lakshmi R, Asst. Professor, Dept. of ISE

64. staticdouble[ ] copyOf(double[ ] source, intlen)
static float[ ] copyOf(float[ ] source, intlen)
static int[ ] copyOf(int[ ] source, intlen)
static long[ ] copyOf(long[ ] source, intlen)
static short[ ] copyOf(short[ ] source, intlen)
static<T> T[ ] copyOf(T[ ] source, intlen)
static <T,U> T[ ] copyOf(U[ ] source, intlen, Class<? extends T[ ]> resultT)
•the type of resultTbecomes the type of the array returned.
30-12-2017 64Lakshmi R, Asst. Professor, Dept. of ISE

65. The copyOfRange( ) method –various forms
static boolean[ ] copyOfRange(boolean[ ] source, intstart, intend)
static byte[ ] copyOfRange(byte[ ] source, intstart, intend)
static char[ ] copyOfRange(char[ ] source, intstart, intend)
static double[ ] copyOfRange(double[ ] source, intstart, intend)
static float[ ] copyOfRange(float[ ] source, intstart, intend)
static int[ ] copyOfRange(int[ ] source, intstart, intend)
static long[ ] copyOfRange(long[ ] source, intstart, intend)
static short[ ] copyOfRange(short[ ] source, intstart, intend)
static<T> T[ ] copyOfRange(T[ ] source, intstart, intend)
static<T,U> T[ ] copyOfRange(U[ ] source, intstart, intend,Class<? extends T[ ]>
resultT)
30-12-2017 65Lakshmi R, Asst. Professor, Dept. of ISE

66. The equals( ) method
•returns true if two arrays are equivalent. Otherwise, it returns false.
static booleanequals(booleanarray1[ ], booleanarray2[ ])
static booleanequals(byte array1[ ], byte array2[ ])
static booleanequals(char array1[ ], char array2[ ])
static booleanequals(double array1[ ], double array2[ ])
static booleanequals(float array1[ ], float array2[ ])
static booleanequals(intarray1[ ], intarray2[ ])
static booleanequals(long array1[ ], long array2[ ])
static booleanequals(short array1[ ], short array2[ ])
static booleanequals(Object array1[ ], Object array2[ ])
30-12-2017 66Lakshmi R, Asst. Professor, Dept. of ISE

67. The fill( ) method –Version 1
•Assigns a value to all elements in an array
•It fills an array with a specified value
static void fill(booleanarray[ ], booleanvalue)
static void fill(byte array[ ], byte value)
static void fill(char array[ ], char value)
static void fill(double array[ ], double value)
static void fill(float array[ ], float value)
static void fill(intarray[ ], intvalue)
static void fill(long array[ ], long value)
static void fill(short array[ ], short value)
static void fill(Object array[ ], Object value)
30-12-2017 67Lakshmi R, Asst. Professor, Dept. of ISE

68. The fill( ) method –Version 2
•assigns a value to a subset of an array
static void fill(booleanarray[ ], intstart, intend, booleanvalue)
static void fill(byte array[ ], intstart, intend, byte value)
static void fill(char array[ ], intstart, intend, char value)
static void fill(double array[ ], intstart, intend, double value)
static void fill(float array[ ], intstart, intend, float value)
static void fill(intarray[ ], intstart, intend, intvalue)
static void fill(long array[ ], intstart, intend, long value)
static void fill(short array[ ], intstart, intend, short value)
static void fill(Object array[ ], intstart, intend, Object value)
30-12-2017 68Lakshmi R, Asst. Professor, Dept. of ISE

69. The sort( ) method –version 1
•Sorts an array so that it is arranged in ascending order.
•It sorts an entire array
static void sort(byte array[ ])
static void sort(char array[ ])
static void sort(double array[ ])
static void sort(float array[ ])
static void sort(intarray[ ])
static void sort(long array[ ])
static void sort(short array[ ])
static void sort(Object array[ ])
static <T> void sort(T array[ ], Comparator<? super T> c)
30-12-2017 69Lakshmi R, Asst. Professor, Dept. of ISE

70. The sort( ) method –version 2
•Enables you to specify a range within an array that you want to sort.
static void sort(byte array[ ], intstart, intend)
static void sort(char array[ ], intstart, intend)
static void sort(double array[ ], intstart, intend)
static void sort(float array[ ], intstart, intend)
static void sort(intarray[ ], intstart, intend)
static void sort(long array[ ], intstart, intend)
static void sort(short array[ ], intstart, intend)
static void sort(Object array[ ], intstart, intend)
static <T> void sort(T array[ ], intstart, intend, Comparator<? super T> c)
30-12-2017 70Lakshmi R, Asst. Professor, Dept. of ISE

71. Why Generic Collections?
•Generics add type safety to the Collection.
•Prior to generics, all collections stored references of type Object. This
allowed any type of reference to be stored in the collection.
•ArrayListlist = new ArrayList(); -in this ArrayListexample, any type of
reference can be stored.
•This can easily lead to errors.
•Consider the following example for pre-generic collection.
30-12-2017 71Lakshmi R, Asst. Professor, Dept. of ISE

72. // Pre-generics example that uses a collection.
import java.util.*;
class OldStyle{
public static void main(String args[]) {
ArrayListlist = new ArrayList();
// These lines store strings, but any type of object
// can be stored. In old-style code, there is no
// convenient way to restrict the type of objects
stored
// in a collection
list.add("one");
list.add("two");
list.add("three");
list.add("four");
Iteratoritr= list.iterator();
while(itr.hasNext()) {
// To retrieve an element, an explicit type
cast is needed
// because the collection stores only Object.
String str= (String) itr.next(); // explicit
cast needed here.
System.out.println(str+ " is " +
str.length() + " chars long.");
}
}
}
30-12-2017 72Lakshmi R, Asst. Professor, Dept. of ISE

73. Why Generic Collections?
Problem with the preceding example:
1.it required that you, rather than the compiler, ensure that only
objects of the proper type be stored in a specific collection.
•For example, in the preceding example, list is clearly intended to store
Strings, but there is nothing that actually prevents another type of
reference from being added to the collection. For example, the compiler
will find nothing wrong with this line of code:
list.add(new Integer(100));
•Because list stores Object references, it can store a reference to Integer as
well as it can store a reference to String. However, if you intended list to hold
only strings, then the preceding statement would corrupt the collection.
30-12-2017 73Lakshmi R, Asst. Professor, Dept. of ISE

74. Why Generic Collections?
2.When you retrieve a reference from the collection, you must
manually cast that reference into the proper type.
3.Because Object can be cast into any type of object, it was possible
to cast a reference obtained from a collection into the wrong type.
For example, if the following statement were added to the
preceding example, it would still compile without error, but
generate a run-time exception when executed: Integer i= (Integer)
itr.next();
30-12-2017 74Lakshmi R, Asst. Professor, Dept. of ISE

75. Why Generic Collections?
•The addition of generics fundamentally improves the usability and
safety of collections because it
•Ensures that only references to objects of the proper type can actually be
stored in a collection. Thus, a collection will always contain references of a
known type.
•Eliminates the need to cast a reference retrieved from a collection. Instead, a
reference retrieved from a collection is automatically cast into the proper
type. This prevents run-time errors due to invalid casts and avoids an entire
category of errors.
•For example, ArrayListis now declared like this:
class ArrayList<E>
•Here, E is the type of element stored in the collection. Therefore, the
following declares an ArrayListfor objects of type String:
ArrayList<String> list = new ArrayList<String>();
30-12-2017 75Lakshmi R, Asst. Professor, Dept. of ISE

76. •Legacy Classes
•Dictionary
•Hashtable
•Properties
•Stack
•Vector
•Legacy Interface
•Enumeration
Legacy classes and interface
30-12-2017 76Lakshmi R, Asst. Professor, Dept. of ISE

77. 30-12-2017 Lakshmi R, Asst. Professor, Dept. of ISE 77
The Collection Algorithms
NOTE: Try to remember 5 to 6 algorithms of your choice

78. 30-12-2017 Lakshmi R, Asst. Professor, Dept. of ISE 78

79. 30-12-2017 Lakshmi R, Asst. Professor, Dept. of ISE 79

80. 30-12-2017 Lakshmi R, Asst. Professor, Dept. of ISE 80

81. 30-12-2017 Lakshmi R, Asst. Professor, Dept. of ISE 81

82. 30-12-2017 82Lakshmi R, Asst. Professor, Dept. of ISE