the container store

© 2001 by Ashby M. Woolf Revision 3

The Container Store

A Place for Everything and Everything in its Place


Containers

Arrays,

Collections and

Maps


Arrays of Primitivespublic class ArraysOfPrimitives { public static void main(String[] args) { int[] a; int[] b = new int[] { 1, 2, 3 }; int[] c = new int[5]; for(int i = 0; i < 5; i++) { c[i] = i * 10; }//! System.out.println("a.length = " + a.length);//! for(int i = 0; i < a.length; i++) System.out.println(a[i]); System.out.println("b.length = " + b.length); for(int i = 0; i < b.length; i++) System.out.println(b[i]); System.out.println("c.length = " + c.length); for(int i = 0; i < c.length; i++) System.out.println(c[i]);//! c.length = 3; }}

Primitive Arrays initialized to zero.



variable a might not have been initialized System.out.println("a.length = " + a.length); ^



cannot assign a value to final variable length c.length = 3; ^



b.length = 3123c.length = 5010203040


Arrays Verses the other Containers

• Most Efficient

• Type Specific

• Size Fixed at Creation

• Bounds Checking

• Other Containers Don't Hold Primitives Directly


Arrays are Objects

• An Array is an Object • An Array Identifier is a Reference to an Object

• An Array is an Object• An Array Identifier is a Reference to an Object




Arrays of Objectspublic class ArraysOfObjects { public static void main(String[] args) { String[] a; String[] b = new String[] { "one", "two", "three" }; String[] c = new String[5]; for(int i = 0; i < 5; i++) { c[i] = "Value = " + (i * 10); }//! System.out.println("a.length = " + a.length);//! for(int i = 0; i < a.length; i++) System.out.println(a[i]); System.out.println("b.length = " + b.length); for(int i = 0; i < b.length; i++) System.out.println(b[i]); System.out.println("c.length = " + c.length); for(int i = 0; i < c.length; i++) System.out.println(c[i]);//! c.length = 3; }}

Arrays of Objects initialized to null.


public class ArraysOfObjects { public static void main(String[] args) { String[] a; String[] b = new String[] { "one", "two", "three" }; String[] c = new String[5]; for(int i = 0; i < 5; i++) { c[i] = "Value = " + (i * 10); }//! System.out.println("a.length = " + a.length);//! for(int i = 0; i < a.length; i++) System.out.println(a[i]); System.out.println("b.length = " + b.length); for(int i = 0; i < b.length; i++) System.out.println(b[i]); System.out.println("c.length = " + c.length); for(int i = 0; i < c.length; i++) System.out.println(c[i]);//! c.length = 3; }}

Arrays of Objects

variable a might not have been initialized System.out.println("a.length = " + a.length); ^


Arrays of Objectspublic class ArraysOfObjects { public static void main(String[] args) { String[] a; String[] b = new String[] { "one", "two", "three" }; String[] c = new String[5]; for(int i = 0; i < 5; i++) { c[i] = "Value = " + (i * 10); }//! System.out.println("a.length = " + a.length);//! for(int i = 0; i < a.length; i++) System.out.println(a[i]); System.out.println("b.length = " + b.length); for(int i = 0; i < b.length; i++) System.out.println(b[i]); System.out.println("c.length = " + c.length); for(int i = 0; i < c.length; i++) System.out.println(c[i]);//! c.length = 3; }}

cannot assign a value to final variable length c.length = 3; ^


public class ArraysOfObjects { public static void main(String[] args) { String[] a; String[] b = new String[] { "one", "two", "three" }; String[] c = new String[5]; for(int i = 0; i < 5; i++) { c[i] = "Value = " + (i * 10); }//! System.out.println("a.length = " + a.length);//! for(int i = 0; i < a.length; i++) System.out.println(a[i]); System.out.println("b.length = " + b.length); for(int i = 0; i < b.length; i++) System.out.println(b[i]); System.out.println("c.length = " + c.length); for(int i = 0; i < c.length; i++) System.out.println(c[i]);//! c.length = 3; }}

Arrays of Objects

b.length = 3onetwothreec.length = 5Value = 0Value = 10Value = 20Value = 30Value = 40


Returning an ArrayAn Array is an Object

class A { public String[] meth() { String[] s = new String[] {"one", "two", "three"}; return s; } • • •}

class B { • • • String[] str; A a = new A() str = a.meth(); • • •}


Array Utilitiesjava.util.Arrays


Copying an Arrayjava.lang.System

public static void arraycopy(Object src,

int src_posit,

Object dst,

int dst_posit,

int length)

Parameters:

src - Source Array

src_posit - Source Array starting position

dst - Destination Array

dst_posit - Destination Array starting position

length - number of components copied.


Filling an Arrayjava.util.Arrays

public static void fill(long[] a,

int fromIndex,

int toIndex,

long val)

Parameters:a - the array to be filled.

fromIndex - index of first element (inclusive) to be filled

toIndex - index of last element (exclusive) to be filled

val - the value to be stored


Comparing Arraysjava.util.Arrays

public static boolean equals(int[] a1,

int[] a2) • • •public static boolean equals(Object[] a1,

Object[] a2)

Parameters:

a1 - one array to be tested for equality.

a2 - the other array to be tested for equality.

Returns:

true if the two arrays are equal. For Objects: (e1==null ? e2==null : e1.equals(e2))


Sorting Arraysjava.util.Arrays

public static void sort(int[] a)

public static void sort(int[] a, int from, int to)

• • •public static void sort(Object[] a)

public static void sort(Object[] a, int from, int to)

Parameters:

a - array to be sorted.

from - first element to be sorted (inclusive).

to - index of end of range to be sorted (exclusive).


How do we compare Arrays of Objects

• Two ways to provide compare functionality

• Array Objects Implement Comparable– "The natural ordering of elements"

– public int compareTo(Object o)

– public static void sort(Object[] a)

• Provide a Class that Implements Comparator– public int compare(Object o1, Object o2)

– public static void sort(Object[] a, Comparator c)


Searching an Arrayjava.util.Arrays

int binarySearch(int[] a, int key) • • •int binarySearch(Object[] a, Object key)

int binarySearch(Object[] a, Object key,Comparator c)

Parameters:a - the array to be searched (must be sorted).

key - the value being searched for

c - the Comparator by which the array is sorted


Array Summary

• Size determined at creation

• Type specific

• Uses TypeName[ ] syntax

• Fast


Arrays

A Change of Topic

Introductionto

Containers


A Review - Interfaces, Abstract Classes, and Classes

class Bird extends Pet { void speak(int i) { for(int k=0; k<i; k++) { System.out.println("Tweet"); } }}

class Dog extends Pet { void speak(int i) { for(int k=0; k<i; k++) { System.out.println("Woof"); } }}

interface Pet { String name; void speak(int i); void setName(String s) { name = s; } String getName() { return name; }}


A Review - Interfaces, Abstract Classes, and Classes

class Bird extends Pet { void speak(int i) { for(int k=0; k<i; k++) { System.out.println("Tweet"); } }}

class Dog extends Pet { void speak(int i) { for(int k=0; k<i; k++) { System.out.println("Woof"); } }}

interface Pet { String name; void speak(int i); void setName(String s) { name = s; } String getName() { return name; }}

abstract class APet implements Pet{

}

abstract class APet implements Pet{ String name;

}

interface Pet { void speak(int i); void setName(String s) { name = s; } String getName() { return name; }}

abstract class APet implements Pet{ String name; public void setName(String s) { name = s; }

}

interface Pet { void speak(int i); void setName(String s); String getName() { return name; }}

abstract class APet implements Pet{ String name; public void setName(String s) { name = s; } public String getName() { return name; }}

interface Pet { void speak(int i); void setName(String s); String getName();}

abstract class APet implements Pet{ String name; public void setName(String s) { name = s; } public String getName() { return name; }}

class Bird extends APet { void speak(int i) { for(int k=0; k<i; k++) { System.out.println("Tweet"); } }}

class Dog extends APet { void speak(int i) { for(int k=0; k<i; k++) { System.out.println("Woof"); } }}

class Bird extends APet { public void speak(int i) { for(int k=0; k<i; k++) { System.out.println("Tweet"); } }}

class Dog extends APet { public void speak(int i) { for(int k=0; k<i; k++) { System.out.println("Woof"); } }}

class Bird extends APet { public void speak(int i) { for(int k=0; k<i; k++) { System.out.println("Tweet"); } }}

class Dog extends APet { public void speak(int i) { for(int k=0; k<i; k++) { System.out.println("Woof"); } }}


Collection

Set

List

AbstractCollection

AbstractListAbstractSet

SortedSet

AbstractSequentialList

HashMapTreeSetHashSetLinkedListArrayList TreeMapWeakHashMap

SortedMap

Map

AbstractMap

Collection

Set

ListSortedSet SortedMap

Map

AbstractCollection



AbstractMap


The Containers


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The Containers

TreeSetHashSetLinkedListArrayList


Introductionto

Containers

A Change of Topic

Collections


Object Object Object Object Object Object • • •

Object F B

Object F BObject nu

ll

B

Object F null

Object L R

Object L RObject L R

Object

Object

ObjectObjectObject

Object

0123456•••n

ArrayList

TreeSet

LinkedList

HashSet

The Collections

1

0

1

0

0

1

1

1

0

1

0

Object null

null Object null

null

Object null

null

Object null

null


Data Structure Reference

http://swww.ee.uwa.edu.au/~plsd210/ds/


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The Containers

boolean add(Object o);boolean remove(Object o);void clear();boolean isEmpty();boolean contains(Object o);boolean containsAll(Collection c);boolean addAll(Collection c);boolean removeAll(Collection c);boolean retainAll(Collection c);Iterator iterator();


A Utility for Filling Collectionsclass Builder {

static void stuffItA(Collection c) {c.add("alpha");c.add("gamma");c.add("delta");c.add("beta");return;

}

static void stuffItB(Collection c) {c.add("beta");c.add("four");c.add("five");c.add("delta");return;

}}


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The ContainersCollection



A Utility for Filling Collectionsclass Builder {


}


}}


Demonstrating the Collectionspublic class DoArrayList { public static void main(String[] args) { Collection a; Collection b; boolean bool; Iterator it; ListIterator lit; Object obj = new String("delta");

System.out.println("\nContainer a is an ArrayList"); a = new ArrayList(); Builder.stuffItA(a); System.out.println("Container b is a ArrayList\n"); b = new ArrayList(); Builder.stuffItB(b); System.out.println("a = " + a); System.out.println("b = " + b);// Demo Operations Here * * * * * }}

Container a is an ArrayListContainer b is a ArrayList

a = [alpha, gamma, delta, beta]b = [beta, four, five, delta]

Hiding the declarationsto make space.


Demonstrating the Collectionspublic class DoArrayList { public static void main(String[] args) { Collection a; Collection b; boolean bool; Iterator it; ListIterator lit;


public class DoArrayList { public static void main(String[] args) { Collection a; Collection b; boolean bool; Iterator it;


public class DoArrayList { public static void main(String[] args) { Collection a; Collection b; boolean bool;


public class DoArrayList { public static void main(String[] args) { Collection a; Collection b;


public class DoArrayList { public static void main(String[] args) { Collection a;


public class DoArrayList { public static void main(String[] args) { // Hidden Declarations


Container a is an ArrayListContainer b is a ArrayList

a = [alpha, gamma, delta, beta]b = [beta, four, five, delta]


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap


addAll()defined in theCollections interface.



Demonstrating addAll() with ArrayListpublic class DoArrayList { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an ArrayList"); a = new ArrayList(); Builder.stuffItA(a); System.out.println("Container b is a ArrayList\n"); b = new ArrayList(); Builder.stuffItB(b); System.out.println("a = " + a); System.out.println("b = " + b);

}}



a.addAll( b ); System.out.println("a = " + a); }} Container a is an ArrayList

Container b is a ArrayList

a = [alpha, gamma, delta, beta]b = [beta, four, five, delta]a = [alpha, gamma, delta, beta, beta, four, five, delta]

Object Object Object • • •

ArrayList


Demonstrating addAll() with LinkedListpublic class DoArrayList { public static void main(String[] args) { // Hidden Declarations


a.addAll( b ); System.out.println("a = " + a); }}

public class DoLinkedList { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an LinkedList"); a = new LinkedList(); Builder.stuffItA(a); System.out.println("Container b is a LinkedList \n"); b = new LinkedList(); Builder.stuffItB(b); System.out.println("a = " + a); System.out.println("b = " + b);


Container a is an LinkedListContainer b is a LinkedList

a = [alpha, gamma, delta, beta]b = [beta, four, five, delta]a = [alpha, gamma, delta, beta, beta, four, five, delta]

Object F B

Object nu

ll

B

Object F nu

ll

LinkedList


Demonstrating addAll() with TreeSetpublic class DoLinkedList { public static void main(String[] args) { // Hidden Declarations



public class DoTreeSet { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an TreeSet"); a = new TreeSet (); Builder.stuffItA(a); System.out.println("Container b is a TreeSet \n"); b = new TreeSet (); Builder.stuffItB(b); System.out.println("a = " + a); System.out.println("b = " + b);


Container a is an TreeSetContainer b is a TreeSet

a = [alpha, beta, delta, gamma]b = [beta, delta, five, four]a = [alpha, beta, delta, five, four, gamma]

Sorted and No Duplicates.

Object L RTreeSet

Object nu

lln

ull

Object nu

lln

ull


Demonstrating addAll() with HashSetpublic class DoTreeSet { public static void main(String[] args) { // Hidden Declarations



public class DoHashSet { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an HashSet"); a = new HashSet (); Builder.stuffItA(a); System.out.println("Container b is a HashSet \n"); b = new HashSet (); Builder.stuffItB(b); System.out.println("a = " + a); System.out.println("b = " + b);


Container a is an HashSetContainer b is a HashSet

a = [gamma, beta, alpha, delta]b = [five, four, beta, delta]a = [gamma, five, four, beta, alpha, delta]

No Duplicates.

HashSet0

1

2

•

•

•

n

Object

Object

Object

Object

1

0

1

1

0

1

0


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap


removeAll()in theCollections interface.



Demonstrating removeAll() with ArrayListpublic class DoArrayList { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an ArrayList"); a = new ArrayList(); Builder.stuffItA(a); System.out.println("Container b is a ArrayList\n"); b = new ArrayList(); Builder.stuffItB(b); System.out.println("a = " + a); System.out.println("b = " + b); a.addAll(b); System.out.println("a = " + a); }}



a.removeAll( b ); System.out.println("a = " + a); }} Container a is an ArrayList

Container b is an ArrayList

a = [alpha, gamma, delta, beta]b = [beta, four, five, delta]a = [alpha, gamma]


ArrayList


Demonstrating removeAll() with LinkedListpublic class DoArrayList { public static void main(String[] args) { // Hidden Declarations


a.removeAll( b ); System.out.println("a = " + a); }}




Container a is an LinkedListContainer b is an LinkedList

a = [alpha, gamma, delta, beta]b = [beta, four, five, delta]a = [alpha, gamma]

Object F B

Object nu

ll

B

Object F nu

ll

LinkedList


Demonstrating removeAll() with TreeSetpublic class DoLinkedList { public static void main(String[] args) { // Hidden Declarations






Container a is an TreeSetContainer b is an TreeSet

a = [alpha, beta, delta, gamma]b = [beta, delta, five, four]a = [alpha, gamma]


Object L RTreeSet

Object nu

lln

ull

Object nu

lln

ull


Demonstrating removeAll() with HashSetpublic class DoTreeSet { public static void main(String[] args) { // Hidden Declarations






Container a is an HashSetContainer b is an HashSet

a = [gamma, beta, alpha, delta]b = [five, four, beta, delta]a = [gamma, alpha]

No Duplicates.

HashSet0

1

2

•

•

•

n

Object

Object

Object

Object

1

0

1

1

0

1

0


Demonstrating retainAll() with ArrayListpublic class DoArrayList { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an ArrayList"); a = new ArrayList(); Builder.stuffItA(a); System.out.println("Container b is a ArrayList\n"); b = new ArrayList(); Builder.stuffItB(b); System.out.println("a = " + a); System.out.println("b = " + b); a.removeAll(b); System.out.println("a = " + a); }}



a.retainAll( b ); System.out.println("a = " + a); }} Container a is an ArrayList

Container b is an ArrayList

a = [alpha, gamma, delta, beta]b = [beta, four, five, delta]a = [delta, beta]


ArrayList


Demonstrating retainAll() with LinkedListpublic class DoArrayList { public static void main(String[] args) { // Hidden Declarations


a.retainAll( b ); System.out.println("a = " + a); }}




Container a is an LinkedListContainer b is an LinkedList

a = [alpha, gamma, delta, beta]b = [beta, four, five, delta]a = [delta, beta]

Object F B

Object nu

ll

B

Object F nu

ll

LinkedList


Demonstrating retainAll() with TreeSetpublic class DoLinkedList { public static void main(String[] args) { // Hidden Declarations






Container a is an TreeSetContainer b is an TreeSet

a = [alpha, beta, delta, gamma]b = [beta, delta, five, four]a = [beta, delta]


Object L RTreeSet

Object nu

lln

ull

Object nu

lln

ull


Demonstrating retainAll() with HashSetpublic class DoTreeSet { public static void main(String[] args) { // Hidden Declarations






Container a is an HashSetContainer b is an HashSet

a = [gamma, beta, alpha, delta]b = [five, four, beta, delta]a = [beta, delta]

No Duplicates.

HashSet0

1

2

•

•

•

n

Object

Object

Object

Object

1

0

1

1

0

1

0





Working with a Single Containerpublic class DoArrayList { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an ArrayList"); a = new ArrayList(); Builder.stuffItA(a); System.out.println("a = " + a); }}

Container a is an ArrayLista = [alpha, gamma, delta, beta]

Demo stuff goes here


interface ListReader ( int read();}class List { private int[] list = new int[100]; private int addPoint = 0; public void add(int i) { list[addPoint++] = i; } public ListReader getReader() { return new Reader(); } private class Reader implements ListReader { private int readPoint = 0; public int read() { return list[readPoint++]; } }}public class DoList { public static void main(String[] args) { List l = new List(); ListReader r1 = l.getReader(); ListReader r2 = l.getReader(); int k; for( k = 0; k < 5; k++ ) { l.add( k * 10 ); } for( k = 0; k < 5; k++ ) { System.out.println(r1.read()); } for( k = 0; k < 5; k++ ) { System.out.println(r2.read()); } }}

010203040010203040

A Simple Containerfrom the Past


Your Classes

Library Classes

Using Class

• Make a Outer Class• Get an inner class and reference made for you• Apply the Inner class methods

The Closure

The Outer Classwith A Method

to return an object reference to an

inner class

An Interface

specifies the inner class method interface

"List"with A Method

to return an object "getReader()"

"DoList"

• Make a Outer Class• Get an inner class and reference made for you• Apply the Inner class methods

r

Inner Classprovides controlled

access to outerclass information

"Reader"provides controlled

access to outerclass information

"ListReader"

specifies the inner class method interface





Working with a Single Containerpublic class DoArrayList { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an ArrayList"); a = new ArrayList(); Builder.stuffItA(a); System.out.println("a = " + a); }}

Container a is an ArrayLista = [alpha, gamma, delta, beta]


iterator(), hasNext(), next() with ArrayListpublic class DoArrayList { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an ArrayList"); a = new ArrayList(); Builder.stuffItA(a); System.out.println("a = " + a); System.out.println("Iterate through an Iterator"); it = a.iterator(); while(it.hasNext()) { System.out.println(" " + it.next()); } }}

Container a is an ArrayLista = [alpha, gamma, delta, beta]Iterate through an Iterator alpha gamma delta beta


The Iterator Interface

• boolean hasNext() – Returns true if the iteration has more elements.

• Object next() – Returns the next element in the interation.

• void remove() – Removes from the underlying collection the last element

returned by the iterator (optional operation).


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The Containers

Iterator iterator();

Collection



Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The Containers

ListIterator listIterator();

List

LinkedListArrayList


ListIterators• void add(Object o)

– Inserts the specified element into the list (optional operation).

• boolean hasNext() – Returns true if this list iterator has more elements when traversing

the list in the forward direction.

• Object next() – Returns the next element in the list.

• int nextIndex() – Returns the index of the element that would be returned by a

subsequent call to next.

• void remove() – Removes from the list the last element that was returned by next

or previous (optional operation).

• void set(Object o) – Replaces the last element returned by next or previous with the

specified element (optional operation).


ListIterators (Cont.)

• boolean hasPrevious() – Returns true if this list iterator has more elements when

traversing the list in the reverse direction.

• Object previous() – Returns the previous element in the list.

• int previousIndex() – Returns the index of the element that would be returned by a

subsequent call to previous.


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The Containers

HashMap TreeMap


Collections

A Change of Topic

Maps


TreeMap

HashMapKey

Key

KeyKeyKey

Key

0123456•••n

Data

Data

DataDataData

Data

DataL RKey

DataL RKeyDataL RKey

The Maps

DataKey null

null

DataKey null

null

DataKey null

null

DataKey null

null


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The Containers

void clear() boolean containsKey(Object key) boolean containsValue(Object value) Set entrySet() boolean equals(Object o) Object get(Object key) int hashCode() boolean isEmpty() Set keySet() Object put(Object key, Object value) void putAll(Map t) Object remove(Object key) int size() Collection values()

Map

HashMap TreeMapWeakHashMap



A Utility for Filling Mapsclass Builder {


}


}}

class Builder {static void stuffItA(Collection c) {

c.put("a", "alpha");c.put("g", "gamma");c.put("d", "delta");c.put("b", "beta");return;

}

static void stuffItB(Collection c) {c.put("b", "beta");c.put("4", "four");c.put("5", "five");c.put("d", "delta");return;

}}

class Builder {static void stuffItA(Map c) {

c.put("a", "alpha");c.put("g", "gamma");c.put("d", "delta");c.put("b", "beta");return;

}

static void stuffItB(Map c) {c.put("b", "beta");c.put("4", "four");c.put("5", "five");c.put("d", "delta");return;

}}


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The ContainersMap



Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The Containers


Map




Demonstrating putAll() with TreeMappublic class DoTreeMap { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an TreeMap"); a = new TreeMap(); Builder.stuffItA(a); System.out.println("Container b is a TreeMap\n"); b = new TreeMap(); Builder.stuffItB(b); System.out.println("a = " + a); System.out.println("b = " + b);

}}

public class DoTreeMap { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an TreeMap"); a = new TreeMap(); Builder.stuffItA(a); System.out.println("Container b is a TreeMap\n"); b = new TreeMap(); Builder.stuffItB(b); System.out.println("a = " + a); System.out.println("b = " + b);

a.putAll( b ); System.out.println("a = " + a); }}

Container a is an TreeMapContainer b is a TreeMap

a = {a=alpha, b=beta, d=delta, g=gamma}b = {4=four, 5=five, b=beta, d=delta}a = {4=four, 5=five, a=alpha, b=beta, d=delta, g=gamma}

TreeMap

DataL RKey

DataKey nu

lln

ull

DataKey nu

lln

ull


Demonstrating putAll() with HashMappublic class DoHashMap { public static void main(String[] args) { // Hidden Declarations

System.out.println("\nContainer a is an HashMap"); a = new HashMap(); Builder.stuffItA(a); System.out.println("Container b is a HashMap\n"); b = new HashMap(); Builder.stuffItB(b); System.out.println("a = " + a); System.out.println("b = " + b);

a.putAll( b ); System.out.println("a = " + a); }}

Container a is an HashMapContainer b is a HashMap

a = {b=beta, a=alpha, g=gamma, d=delta}b = {b=beta, 5=five, 4=four, d=delta}a = {b=beta, 5=five, a=alpha, 4=four, g=gamma, d=delta}

0

1

2

•

•

•

n

HashMapKey

Key

Key

Key

Data

Data

Data

Data


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The Containers


Map




System.out.println("Container a is an HashMap");a = new HashMap(); Builder.stuffItA(a);System.out.println("ksa is a Collection a.keySet()");Collection ksa = a.keySet();System.out.println("b is an HashMap");b = new HashMap(); Builder.stuffItB(b);System.out.println("ksb is a Collection b.keySet()");Collection ksb = b.keySet();System.out.println("a = " + a);System.out.println("ksa = " + ksa);System.out.println("b = " + b);System.out.println("ksb = " + ksb);System.out.println("ksa.removeAll(ksb);");ksa.removeAll( ksb );System.out.println("ksa = " + ksa);System.out.println("a = " + a);

Container a is an HashMapksa is a Collection a.keySet()Container b is an HashMapksb is a Collection b.keySet()a = {b=beta, a=alpha, g=gamma, d=delta}ksa = [b, a, g, d]b = {b=beta, 5=five, 4=four, d=delta}ksb = [b, 5, 4, d]ksa.removeAll(ksb);ksa = [a, g]a = {a=alpha, g=gamma}

keySet()


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The Containers


Map




System.out.println("Container a is an HashMap");a = new HashMap(); Builder.stuffItA(a);System.out.println("ksa is a Collection a.keySet()");Collection ksa = a.keySet();System.out.println("b is an HashMap");b = new HashMap(); Builder.stuffItB(b);System.out.println("ksb is a Collection b.keySet()");Collection ksb = b.keySet();System.out.println("a = " + a);System.out.println("ksa = " + ksa);System.out.println("b = " + b);System.out.println("ksb = " + ksb);System.out.println("ksa.removeAll(ksb);");ksa.removeAll( ksb );System.out.println("ksa = " + ksa);System.out.println("a = " + a);

System.out.println("Container a is an HashMap");a = new HashMap(); Builder.stuffItA(a);System.out.println("vca is a Collection a.values()");Collection vca = a.values();System.out.println("b is an HashMap");b = new HashMap(); Builder.stuffItB(b);System.out.println("vca is a Collection b.values()");Collection vca = b.values();System.out.println("a = " + a);System.out.println("vca = " + vca);System.out.println("b = " + b);System.out.println("vcb = " + vcb);System.out.println("vca.removeAll(vcb);");vca.removeAll(vcb);System.out.println("vca = " + vca);System.out.println("a = " + a);

Container a is an HashMapvca is a Collection a.values()Container b is an HashMapvcb is a Collection b.values()a = {b=beta, a=alpha, g=gamma, d=delta}vca = [beta, alpha, gamma, delta]b = {b=beta, 5=five, 4=four, d=delta}vcb = [beta, five, four, delta]vca.removeAll(vcb);vca = [alpha, gamma]a = {a=alpha, g=gamma}

value()


Collection

Set

List

AbstractCollection


SortedSet



SortedMap

Map

AbstractMap

The Containers


Map




System.out.println("Container a is an HashMap");a = new HashMap(); Builder.stuffItA(a);System.out.println("vca is a Collection a.values()");Collection vca = a.values();System.out.println("b is an HashMap");b = new HashMap(); Builder.stuffItB(b);System.out.println("vca is a Collection b.values()");Collection vca = b.values();System.out.println("a = " + a);System.out.println("vca = " + vca);System.out.println("b = " + b);System.out.println("vcb = " + vcb);System.out.println("vca.removeAll(vcb);");vca.removeAll(vcb);System.out.println("vca = " + vca);System.out.println("a = " + a);

System.out.println("Container a is an HashMap");a = new HashMap(); Builder.stuffItA(a);System.out.println("esa is a Collection a.entrySet()");Collection esa = a.entrySet();System.out.println("b is an HashMap");b = new HashMap(); Builder.stuffItB(b);System.out.println("esa is a Collection b.entrySet()");Collection esa = b.entrySet();System.out.println("a = " + a);System.out.println("esa = " + esa);System.out.println("b = " + b);System.out.println("esb = " + esb);System.out.println("esa.removeAll(esb);");esa.removeAll(esb);System.out.println("esa = " + esa);System.out.println("a = " + a);

Container a is an HashMapContainer esa is a Collection a.entrySet()Container b is an HashMapContainer esb is a Collection b.entrySet()a = {b=beta, a=alpha, g=gamma, d=delta}esa = [b=beta, a=alpha, g=gamma, d=delta]b = {b=beta, 5=five, 4=four, d=delta}esb = [b=beta, 5=five, 4=four, d=delta]esa.removeAll(esb);esa = [a=alpha, g=gamma]a = {a=alpha, g=gamma}

entrySet()


The WeakHashMap

• Key in a HashMap are Objects

• If the only reference to a key Object is

from a WeakHashMap the Object can

be Garbage Collected

• The WeakHashMap entry for that key

will be removed.


Summary

• Arrays– Fast Simple– Type Specific

• Collections– Lists– Sets

• Maps– Key-Data Pairs


Stuff to Add Next Time

• Multidimensional Arrays

• Cross Collection Operations

• ListIterator Example

• Iterate with a collection view of a Map

• Include examples of Class specific operations


End of Content

the container store

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