1. Pertemuan 3
Array dkk
jual [Valdo] Lunatik Chubby Stylus

2. ARRAY Tipe data turunan. Contoh deklarasi : int x[20];
SATU variabel untuk menyimpan BANYAK data dengan TIPE data yang SAMA. Mempunyai INDEKS.
Struktur data :
Alokasi memori bersifat statis/ tetap.
Konsep : string, array multidimensi 4 3 2 1 7

3. Contoh program Program menghitung rata-rata nilai. Algoritma :
Deklarasikan variabel array untuk menyimpan data-data nilai.
Input data nilai dengan perintah looping. Akses elemen dengan operator kurung siku ([]).
Hitung penjumlahan data-data nilai.
Hitung rata-rata = jumlah total/ jumlah data.

4. STRUCT Tipe data turunan. Contoh deklarasi : struct { int jari_jari;
float luas;
float keliling;
} lingkaran;

5. STRUCT Contd.
SATU variabel bisa menyimpan BANYAK data yang BERBEDA TIPE datanya. Mempunyai ELEMEN.
Struktur data :
Konsep : struct of struct (nested struct). 10
314.0
62.8

6. Contoh program Program tentang lingkaran. Algoritma :
Inventarisasi atribut-atribut yang dimiliki oleh sebuah objek lingkaran.
Akses masing-masing elemen dengan memakai operator tanda titik (.).

7. ARRAY OF STRUCT
Struktur data berupa array yang setiap elemennya bertipe struct.
Contoh deklarasi :
struct {
int NPM;
char nama[30];
float IPK;
} mhs[100];

8. Array of Struct Contd. Struktur data :
Untuk akses elemen dimulai dari indeks array kemudian diikuti nama elemennya  mhs[3].NPM = 1234;
100
Abdullah
3.80
101
Budi
3.45
102
Candra
3.22
103
Daud
3.17

9. Contoh Program
Program data mahasiswa.
Program tabel fungsi kuadrat.

10. Tugas Kelompok - RESUME
ARRAY
Array as function parameter
String
Two dimensional array
STRUCT
Array of structure
Unions
Struct as function parameter

11. Review BP
Dari slide pak cahyo pertemuan 7 dan pertemuan 2 dengan sedikit modifikasi

12. Array
Review BP

13. Arrays
An array is a special kind of object that is used to store a collection of data.
The data stored in an array must all be of the same type, whether primitive or reference data types.
For example, we may want to store:
An array of double values
An array of int values

14. The Need for Arrays
Write a Java program that asks the user for 10 exam scores and displays the average.
What if you are also required to display all the scores which are higher than the average?
What if you are to record 100 scores?

15. The Problem:
import java.util.;
public class ExamScoresForLoop {
public static void main(String[] args)
Scanner keyboard = new Scanner (System.in);
double score;
double total = 0.0;
for(int i = 1; i <= 10; i++)
System.out.println("Enter score " + i +":");
score = keyboard.nextDouble();
total = total + score; }
System.out.println("The average score is " + total/10);
// how to display scores which are greater than average???
We need to keep track of each score that is entered by the user in an efficient manner.

16. Using Arrays
Instead of only storing one score:
score
0x0010
98.9
We need to store a collection of scores, or what is called an array.
in this case, score is considered to be a reference to the array at the memory address stored.
score
0x0010
0x0h40
98.9
50.5
75.0
59.5
65.4
0x0h40
0x0h41
0x0h42
0x0h43
0x0h44

17. Accessing Array Elements
Once an array has been declared, we can store and access data in it.
We must specify the index representing the position of the data.
The index always begins from 0.
Index representing position of the data
score
score[0]
98.9
50.5
75.0
59.5
65.4 1 2 3 4
score[3]

18. Declaring Arrays An array is declared by: Syntax: Examples
specifying the type of data it will hold
specifying the name of the array with an identifier
including square brackets [ ]
Syntax:
<data type>[] <identifier>;
Examples
int[] num; // an array of ints
double[] score; // an array of doubles
Student[] st; // an array of Student objects

19. Creating Arrays
In Java, the array is an object and must be instantiated with its size.
Syntax:
<identifier> = new <data type>[<size>];
Therefore, an array may be declared and instantiated in one statement:
int[] num = new int[10];
//creates an array to store 10 integers
It may also be instantiated in two steps:
int[] num;
num = new int[10];

20. Initializer Lists
An array can also be created by using an initializer list that fills in the values of the elements in the array in one line.
When an initializer list is used, the new operator and size of the array are not specified.
Examples:
int[] num = {3, 6, 5, 7, 2, 8, 10, 20}
char[] letterGrades = {'A', 'B', 'C', 'D', 'F'}

21. Bounds Checking An array that has been instantiated has a fixed size.
int[] num = new int[10] has array elements from num[0] to num[9] only.
The Java interpreter will indicate an out-of-bounds error at run-time if the array index is not valid.
Each array object has an attribute length that stores the size of the array, or the number of elements.
Therefore an array will have valid indices from 0 to (length-1) only.

22. Traversing Arrays We can use a for loop to traverse the array
For example, we may display each element of the array:
for (int i = 0; i < maks; i++) {
System.out.println(data[i]); }
We may even use a for loop to allow the user to enter the elements of the array via interactive input.

23. Searching an Array We may need to check if an element is in the array:
We can use the following logic to check whether a name that the user enters is in the array of names declared and filled earlier:
ask user for the required name
Start from i = 0
assume that it is not found
While the required name is not found and i < length of array
if the value at position i corresponds to the required name
then the name is found
otherwise,
check the next element (i = i + 1)

24. Calculations
We often need to perform calculations using some or all of the elements of the array:
total of all elements
the average
the element with the largest or smallest value
Assume that an array of double values has been declared and filled:
double[] score = new double[10];

25. Finding the Total and Average
In order to find the total, we must initialize and keep track of the running total.
The total is then used to calculate the average.
double total = 0.0;
for (int i = 0; i < score.length; i++) {
total = total + score[i]; }
System.out.println("The total is " + total);
double avg = total / score.length;
System.out.println("The average is " + avg);

26. Arrays and Methods
Arrays can be used as parameters in methods: the entire array is passed to the method.
For example, write a method findEmp that receives two parameters:
the first parameter is an array of Strings representing names of employees
the second parameter is a String representing the name of the employee required
The method should return the position of the employee whose name is found based on the second parameter.

27. Arrays as Parameters The method can be defined as follows:
public static int findEmp(String[] name, String wanted) {
for(int i = 0; i < name.length; i++)
if (wanted.equalsIgnoreCase(name[i]))
return i; // found at pos i
return -1; // not found }

28. Arrays as Returned Objects
Arrays can also be returned by methods, as long as the array type is specified as the return type.
The following method takes as input an array of Strings and returns another array with the lengths of each of the Strings in the array.
public static int[] findLengths(String[] strArray)
{ int[] strLength = new int[strArray.length];
for (int i = 0; i < strArray.length; i++)
strLength[i] = strArray[i].length();
return strLength; }

29. Initial Values of Array Elements
All elements in an array are automatically initialised with default values.
An array of numeric data has default elements with value double[] score = new double[10]; all elements in score will have value 0.0
Arrays of boolean will be initialized to false.
Arrays of reference data types will be initialized to null.

30. CLASS
Review BP

31. Class adalah template untuk pembuatan obyek Class memiliki anggota :
Atribut
Method

32. Anatomy of a Java Class
A Java console application must consist of one class that has the following structure:
/* This is a sample program only.
Written by:
Date: */
public class SampleProgram {
public static void main(String [] args)
int num1 = 5; // num stores 5
System.out.print("num1 has value ");
System.out.println(num1); }
multi-line comments
name of the class
in-line comments
statements to be executed

33. Anatomy of a Java Class
A Java console application must consist of one class that has the following structure:
/* This is a sample program only.
Written by:
Date: */
public class SampleProgram {
public static void main(String [] args)
int num1 = 5; // num stores 5
System.out.print("num1 has value ");
System.out.println(num1); }
class header
main method

34. Contoh class tabungan class BankAccount {
private double balance; // account balance
public BankAccount(double openingBalance) { // constructor
balance = openingBalance; }
public void deposit(double amount) { // makes deposit
balance = balance + amount;
public void withdraw(double amount) { // makes withdrawal
balance = balance – amount;
public void display(){ // displays balance
System.out.println("balance=" + balance);
} // end class BankAccount

35. Contoh penggunaan class tabungan
class BankApp {
public static void main(String[] args)
// create acct
BankAccount ba1 = new BankAccount(100.00);
System.out.print("Before transactions, ");
// output : Before transactions, balance=100
ba1.display(); // display balance
ba1.deposit(74.35); // make deposit
ba1.withdraw(20.00); // make withdrawal
System.out.print("After transactions, ");
// output : After transactions, balance=154.35
} // end main()
} // end class BankApp