1 The copy constructor in the - PowerPoint Presentation

Slide1

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The copy constructor in the BankAccounts class.Two alternatives here:

/** copy constructor */public BankAccounts(BankAccounts L){ theAccounts = L.theAccounts.clone(); size=L.size;}

/** alternative copy constructor */public BankAccounts(BankAccounts L){ theAccounts = L.theAccounts; size = L.size;}

or

Will examine their effects using TestBankAccounts programme:

ADS2 Lecture 2

(a)

(b)

Handout for Lecture 2.

SLIDE 10Slide2

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public class TestBankAccounts {

public static void main(String[] args) { // Test BankAccount Class BankAccount bankAccount1=new BankAccount("1456","Michael Smith",300); BankAccount bankAccount2=new BankAccount

("1457","Jane Edwards",1000); BankAccount bankAccount3=new BankAccount("1458","Sam Forge",2000); BankAccounts myAccounts1 = new BankAccounts(3); myAccounts1.setAccount(0,bankAccount1); myAccounts1.setAccount(1,bankAccount2); myAccounts1.setAccount(2,bankAccount3); BankAccounts myAccounts2=

new BankAccounts(myAccounts1); myAccounts1.withdraw(0,250.0);

myAccounts1.withdraw(1,250.0); myAccounts1.withdraw(2,250.0);

*

(ignore asterisks for now)

ADS2 Lecture 2

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System.out

.println("The final bank accounts are: ");System.out.println("myAccounts1: ");System.out.println(myAccounts1);System.

out.println("myAccounts2: ");System.out.println(myAccounts2);}}Exercise:What is the output if we use the first copy constructor on slide 10?What is the output if we use the second copy constructor on slide 10?**ADS2 Lecture 2

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As a data structure, ArrayList is a generic storage device

think of as an extendible arrayimplemented by arraysWill see later arraylist ADT – don’t assume implemented using array. ArrayList is class in standard Java – need import java.util.ArrayList; For an array, size is fixed at declaration:

theAccounts = new BankAccount[3]; Initialises an array of size 3 of BankAccounts objects For an ArrayList specify type of entry and initial size at declaration: ArrayList<String> list = new ArrayList<String>(20); If capacity exceeds 20, new array is built.

Note base type must be reference type (not primitive type). If you want to use a primitive type, must use wrapper class (e.g. Integer for

int).

ADS2 Lecture 2

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Some ArrayList methods

/** Create ArrayList of specified Base-Type and initialCapacity */public ArrayList<Base-Type>(int initialCapacity)/** Create ArrayList of specified Base-Type and init capacity 10 */public ArrayList<Base-Type

>()/** Return element at specified index */public Base-Type get(int index)/** Set the element at specified index to newElement and return * the value previously at that position; (often used as if void)*/public Base-Type set(int index,

Base-Type newElement)

/** Add newElement at position index, moves elements to make room, * and increments size;increases capacity if necessary */

public void

add(int

index, Base-Type newElement)

/** Add newElement at position size and increments size; * (increases capacity if necessary) */

public

void

add(

Base-Type

newElement)

From JP2

ADS2 Lecture 2

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/** Remove and return element at specified index; move elements

* down to close the gap */public Base-Type remove(int index)/** return the number of elements in the ArrayList*/public

int size()/** return true if the ArrayList is empty, and false otherwise*/public boolean isEmpty()/** make the ArrayList empty */public

void

clear()/** trim the capacity of the

ArrayList to its current size */

public void

trimToSize()

/**

Return the index of the first occurrence of o in the

ArrayList

, or -1 if this list does not contain the element.

*/

public

int

indexOf

(Object o)

/**

Remove the first occurrence of o from the

ArrayList

, if it is present; returns true if it was removed, false otherwise

*/

public

boolean

remove(Object o)

ADS2 Lecture 2

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Example for you:

replace code in Bank Accounts example between * and ** with code in which:ArrayList myAccounts of size 3 is initialised to take data of type BankAccountbankAccount1 .. bankAccount3 are added to the list

Set element at index 0 to bankAccount4 = (“1455”,”Edwin Moore”,600)Remove entry with index 2Contents of myAccounts printed to standard output.What is output?ADS2 Lecture 2SLIDE 19