Khalid Mughal Chapter 1

Page 1 of 17

Chapter 1. Basics of Java Programming Supplementary Objectives

! "

!

1.1 Introduction #

! ! "

! !

( )

"

#

$ %%&' ! ! #

!

(

! #

" !

1.2 Classes %

"

"

"

(

*

! %%& ! *

* ! *

(

! ! *

!

"

!

! ! +

# " ! *

" !

! !

!

,

$

'

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

# "

6/16/2006

Page 2 of 17

!

!

-

! *

(

" "

!

#

#" #.

$ ./ '

"

.

/ 00 "

+ 00

CharStack +

Declaring Members: Fields and Methods 1(

00

"

+

CharStack !

00 !

# *

CharStack " stackArray "

#$

topOfStack "

#$

' (

' CharStack

!

# #

push() pop()

!

# #

peek() isEmpty() isFull()

" "

# #

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006

Page 3 of 17

# * "

"

$ 2' 3 (

4" !

"

(

// Source Filename: CharStack.java public class CharStack { // Class name // Class Declarations: // (1) Fields: private char[] stackArray; private int topOfStack;

// The array implementing the stack. // The top of the stack.

// (2) Constructor: public CharStack(int n) { stackArray = new char[n]; topOfStack = -1; } // (3) public public public public public

Methods: void push(char element) char pop() char peek() boolean isEmpty() boolean isFull()

{ { { { {

stackArray[++topOfStack] = element; } return stackArray[topOfStack--]; } return stackArray[topOfStack]; } return topOfStack < 0; } return topOfStack == stackArray.length - 1; }

}

1.3 Objects Class Instantiation * * !

$ '

5

! !

"

! ! !

// Declaration of two reference variables that will denote // two distinct objects, namely two stacks of characters, respectively. CharStack stack1, stack2; , ! !

new

"

// Create two distinct stacks of chars. stack1 = new CharStack(10); // Stack length: 10 chars

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006

Page 4 of 17 stack2 = new CharStack(5);

// Stack length: 5 chars "

new

CharStack

! 1

) " topOfStack

" #

stack1

stack2 "

!

" stackArray

6

new " CharStack

" new ! ! topOfStack

6

CharStack stack1 = new CharStack(10), stack2 = new CharStack(5); +

02

"

./

! +

! ! ! +

02 ( +

"

" "

':'

02

3

! 02 "

CharStack

(

" CharStack

"

Object References

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006

Page 5 of 17

*

!

! !

"

!

* !

!

!

// Create two distinct stacks of chars. CharStack stackA = new CharStack(12); // Stack length: 12 chars CharStack stackB = new CharStack(6); // Stack length: 6 chars stackB = stackA; // (1) aliases after assignment // Stack previously referenced by stackB can now be garbage collected. "

#

! +

07 * #

+

"

!

$ 0' 07 8

! ! 9

$ 0' stackA stackA

stackB " stackB #

:9

stackB

;

!

#

! "

1.4 Instance Members 1

"

"

!

" !

!

!

!

!

!

! "

"

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006

Page 6 of 17

!

"

! "

3

3

0<

Invoking Methods %

( !

!#

! (

*

'.'

!

!# !#

#

!

!

!

CharStack stack = new CharStack(5); // Create a stack stack.push('J'); // (1) Character 'J' pushed char c = stack.pop(); // (2) One character popped and returned: 'J' stack.printStackElements(); // (3) Compile time error: No such method in CharStack ! $ 0' #

!#

stack ! $ 2' CharStack

# push()

pop()

pop() ! printStackElements() CharStack

push() !#

#

"

'.' !

!

CharStack

private stack.topOfStack++;

// Compile time error: topOfStack is a private field.

1.5 Static Members *

"

!

( !

# "

+

0=

"

"

# !

! 9 static 3 * !

3 3

" 5

#

"

1 :

!

!

6

"

!

# " # "

"

CharStack "

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

static

CharStack

!

6/16/2006

Page 7 of 17

1(

02

counter 0" !

6

!

!

$ 2' ( getInstanceCount() "

#

+

0<

$% &

"

" CharStack (

$ 7'

$

"

CharStack !

00

!

$ 0' 1

$ // Source Filename CharStack.java public class CharStack { // Instance variables private char[] stackArray; // The array implementing the stack. private int topOfStack; // The top of the stack. // Static variable private static int counter;

// (1)

// Constructor now increments the counter for each object created. public CharStack(int capacity) { // (2) stackArray = new char[capacity]; topOfStack = -1; counter++; } // Instance methods public void push(char element) public char pop() public char peek() public boolean isEmpty() public boolean isFull()

{ { { { {

stackArray[++topOfStack] = element; } return stackArray[topOfStack--]; } return stackArray[topOfStack]; } return topOfStack < 0; } return topOfStack == stackArray.length - 1; }

// Static method public static int getInstanceCount() { return counter; }

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

(3)

6/16/2006

Page 8 of 17 }

'

,

" getInstanceCount()

!#

CharStack

int count = CharStack.getInstanceCount(); // Class name to invoke static method 3

!

CharStack stack1 = new CharStack(10); int count1 = stack1.getInstanceCount();

// Reference invokes static method

3

!

(

(

)

! /

!# *

"

>

*

"

'

non-static field

*

%

/ 3 /

! !#

3 >

*

3 /

* " class method

" *

static field

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

class variable *

6/16/2006

Page 9 of 17

1.6 Inheritance "

" # !

GearBox "

Vehicle Vehicle !

#

( " # " + CharStack

#

!

?

0@

#

# #

! ;!

# #

+%

"

(

CharStack

CharStack

*

!

Car Motor Axle

! PrintableCharStack CharStack PrintableCharStack

"

!

( Vehicle

(

,

)

extends

* "

PrintableCharStack

class PrintableCharStack extends CharStack { // Instance method public void printStackElements() { // ... implementation of the method... }

// (1) // (2)

// The constructor calls the constructor of the superclass explicitly. public PrintableCharStack(int capacity) { super(capacity); } // (3) } PrintableCharStack printStackElements() stackArray

(

CharStack PrintableCharStack CharStack 4 " ! CharStack

"

1(

07

$ 0' )

CharStack ! printStackElements()

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006

Page 10 of 17

"

$ 2' CharStack

!

$ 7'

PrintableCharStack 6 #

$

// Source Filename: CharStack.java public class CharStack { // Instance variables protected char[] stackArray; // The array that implements the stack. protected int topOfStack; // The top of the stack. // The rest of the definition is the same as in Example 1.2. } // Source Filename: PrintableCharStack.java public class PrintableCharStack extends CharStack { // (1) // Instance method public void printStackElements() { // (2) for (int i = 0; i <= topOfStack; i++) System.out.print(stackArray[i]); // print each char on terminal System.out.println(); } // Constructor calls the constructor of the superclass explicitly. PrintableCharStack(int capacity) { super(capacity); } // (3) } % "

"

PrintableCharStack !

#

CharStack

PrintableCharStack aPrintableCharStack = new PrintableCharStack(3); aPrintableCharStack.push('H'); aPrintableCharStack.push('i'); aPrintableCharStack.push('!'); aPrintableCharStack.printStackElements(); // Prints "Hi!" on the terminal

1.7 Aggregation 9

"

! ( 1

(

!

!

CharStack 1 # # !

!

int CharStack

" !

! ./

"

(! "

CharStack

"

!

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

+ char

0A "

6/16/2006

Page 11 of 17

-

"

1.8 Tenets of Java ,

! " #

!

!

!

!

8 %

!

%

!

?

!

5

Review Questions

9

:

3

" *

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006

Page 12 of 17

* * . *

!

*

#

9

:

3

" *

"

* *

6

. * *

!

! 9

:

public class Counter { int current, step;

// (1)

public Counter(int startValue, int stepValue) { set(startValue); setStepValue(stepValue); }

// (2)

public int get() { return current; }

// (3)

public void set(int value) { current = value; }

// (4)

public void setStepValue(int stepValue) { step = stepValue; }

// (5)

} 3

" ,

#

"

$ 0'

,

#

"

$ 2'

,

#

"

$ 7'

. ,

#

"

$ ='

,

#

"

$ <'

# ;!

Thing

"

"

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

!

6/16/2006

Page 13 of 17

"

:

Thing item, stuff; item = new Thing(); Thing entity = new Thing(); 3

"

"

% "

. %

!

"

! !

' 9

:

3

" * *

"

*

!

. *

"

*

"

* 4"

!:

3

" !

-

. - ;!

"

"

:

class A { int value1; }

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006

Page 14 of 17

class B extends A { int value2; } 3

"

"

,

A (

,

B

,

A

. ,

B

B A B A

%

A

!

value2

%

B

!

value1

1.9 Java Programs * ! ( 35B

" *

! 2

! " " .class ! 235B !

(

00C3

public .java

(

(

1

*

! *

1.10 Sample Java Application * (

" ! main

! (

main()

Essential Elements of a Java Application 1(

0=

(

"

CharStack

!

#" "

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006

Page 15 of 17 // Source Filename: Client.java public class Client { public static void main(String[] args) { // Create a stack CharStack stack = new CharStack(40); // Create a string to push on the stack String str = "!no tis ot nuf era skcatS"; int length = str.length(); System.out.println("Original string: " + str); // Push the string char by char onto the stack for (int i = 0; i
Client !# $>/'

main

main()

!

! >

/

"

main()

public static void main(String[] args) { // ... } main() static !

# "

public # " String[] args main()

void

"

Compiling and Running an Application ! 35B

!

Client.java

javac "

! 2

Client

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006

Page 16 of 17

!

"

>javac Client.java Client.class CharStack

Client " , 35B 1(

! CharStack.class CharStack.java

( 0=

! !

Client (

java "

! 2

"

>java Client D 1(

0=

( "

main() (

main()

Review Questions

/ 9

! 235B SmallProg.java:

"

public class SmallProg { public static void main(String[] args) { System.out.println("Good luck!"); } } 3

" java SmallProg javac SmallProg java SmallProg.java . javac SmallProg.java java SmallProg main

0 9

! 235B

(

main()

SmallProg: 3

"

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006

Page 17 of 17

java SmallProg javac SmallProg java SmallProg.java . java SmallProg.class java SmallProg.main()

Chapter Summary

"

" %%&

"

!

! !

Programming Exercises

/

1( CharStack . 6 PrintableCharStack 1( 0=:

PrintableCharStack 0= printStackElements() " ! "

file://C:\Documents and Settings\cdot\Local Settings\Temp\~hh82B4.htm

6/16/2006