Referensi Bahasa Pemrograman Java

Referensi Bahasa Pemrograman Java Tipe Data Primitif Type

Bits

Bytes

Minimum Range

Maximum Range

byte short int long float double char boolean

8 16 32 64 32 64 16 8

1 2 4 8 4 8 2 1

-128 or -27 -32,768 or -215 -2,147,483,648 or -231 -263 -3.4E38 -1.7E308 n/a n/a

127 or 27-1 32,767 or 215-1 2,147,483,647 or 231-1 263-1 3.4E38 1.7E308 n/a n/a

Operator Aritmatika Operator

Name

# Operands

Description

+ * / %

Addition Subtraction Multiplication Division Modulus

2 2 2 2 2

++ -+ -

Increment Decrement Positive Sign Negative Sign

1 1 1 1

Add two operands Subtract the right operand from the left Multiplies the right operand and left operand Divides the right operand into the left operand Returns the value that is left over after dividing the right operand into the left operand Adds 1 to the operand (x = x + 1) Subtracts 1 from the operand (x = x -1) Promotes byte, short, and char types to the int type Changes a positive value to negative, and vice versa

Karakter Khusus Sequence

Character

\n \t \r \” \\

New line Tab Return Quotation Mark Backslash

Assignment Operators Operator

Name

Description

= +=

Assignment Addition

-=

Subtraction

*=

Multiplication

/=

Division

%=

Modulus

Assigns a new value to the variable Adds the operand to the starting variable value of the variable and assigns the result to the variable Subtracts the operand from the starting value of the variable and assigns the result to the variable Multiplies the operand by the starting value of the variable and assigns the result to the variable Divides the operand by the starting value of the variable and assigns the result to the variable Derives the value that is left over after dividing the right operand by the value in the variable, and then assigns this value to the variable

Ekspresi Boolean Operator

Name

Description

== != >

Equality Inequality Greater Than

<

Less Than

>=

Greater Than Or Equal

<=

Less Than or Equal

Returns a true value if both operands are equals Returns a true value if the left and right operands are not equal Returns a true value if the left operand is greater than the right operand Return a true value if the left operand is less than the right operand Returns a true value if the left operand is greater than or equal to the right operand Return a true value if the left operand is less than or equal to the right operand

Operator AND dan OR Operator

Name

Example

Description

&& || ^ !

AND OR XOR NOT

a && b a || b a^b !a

true if both a and b are true true if either a or b (or both) is true true if only a or b is true true if a is not true

String  String bukan merupakan tipe data primitif melainkan tipe data reference  Contoh: String message1 = "Invalid data entry";  Untuk menyambung (concat) dua/lebih string, gunakan operator +  Untuk membandingkan 2 buah String, kita harus menggunakan method “equals” atau

“equalgnoreCase” yang dimiliki oleh kelas String.

Variabel & Assignment  Sintaks: tipeData namaVariabel  Contoh:  int counter = 1;  boolean valid = false;  char letter = ‘A’;  char letter = 65;  double distance = 3.65e+9;

Method print, println,dan printf  print  posisi akhir kursor berada di garis yang sama o

Contoh: System.out.print ("Hello World");

 println  posisi akhir kursor berada di garis yang baru (seolah menekan enter) o

Contoh: System.out.println("Hello World");

 printf  print dalam bentuk format tertentu (f = formatted) o

Contoh: System.out.printf("%s\n %s\n", "Hello", "World");

Using Console for Input & Output  Dengan java versi 5, cara paling mudah untuk mendapatkan input dari console adalah dengan menggunakan Scanner class  Untuk menampilkan output ke console adalah menggunakan method (fungsi) System.out.println  Sebelum menggunakan Scanner class, kita harus melakukan proses import sbb: import java.util.Scanner;  Untuk membaca input dari console, kita buat objek scanner dengan cara menuliskannya sbb: Scanner sc = new Scanner(System.in);  Ada 4 buah methods dari objek Scanner (yaitu sc) yang dapat kita gunakan sesuai kebutuhan: Method

Description

next() or nextLine() nextInt() nextDouble() nextBoolean()

Reads a String value from the user Reads an integer value from the user Reads a double value from the user Reads a boolean value from the user

Struktur Kontrol Selection Java memiliki 5 conditional statements yaitu: if, else, switch, case, dan break. 1. IF

2. IF-ELSE

3. SWITCH-CASE switch (expr) { //note: expr hanya boleh berupa int atau char case value1: statement_1a; statement_1b; break; case value2: statement_2; break; default: statement_da; statement_db; break; }

Struktur Kontrol Loop 1. While Loop while (true){ // statements } 2. Do-While Loop do { //statements (body) } while (expression); 3. For Loop

Note: 

Init: statement untuk menginisialisasi variabel loop, dieksekusi sekali



Cont: Ekspresi Boolean untuk keberlanjutan loop, dieksekusi sebelum pengulangan



Adj: statement untuk meng-adjust variabel loop, dieksekusi setelah pengulangan

Array Array adalah variabel yang yang dikelompokkan bersama dalam suatu nama. Ada 4 Tahap Manipulasi Array: 1. Array declaration 2. Array creation 3. Array initialization 4. Array processing Contoh Deklarasi Array:  String[] students;

// An array of String variables

 int[] values;

// An array of integer variables

 boolean[] truthTable; // An array of boolean variables  char[] grades;

// An array of character variables

Contoh Pembuatan Array:  String[] names = new String[10];  Int[] numbers = new int[20]; Contoh Inisialisasi Array:  Cara 1: assign satu per satu: String[] days = new String[7]; days[0] = "Sunday"; days[1] = "Monday"; days[2] = "Tuesday"; days[3] = "Wednesday"; days[4] = "Thursday"; days[5] = "Friday"; days[6] = "Saturday";  Cara 2: shorthand way menggunakan { }: String[] days = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };

Contoh Pemrosesan & Menampilkan Isi Array Menggunakan FOR-LOOP: String[] days = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday","Friday", "Saturday" }; for (int i = 0; i < days.length; i++{ System.out.println(days[i]); }

Contoh Pemrosesan & Menampilkan Array Menggunakan: Enhanced FOR-LOOP (FOREACH): String[] days = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday","Friday", "Saturday" }; for (String dayElement: days){ System.out.println(dayElement); }

Exception Handling  Exceptional adalah kesalahan (error) yang disebabkan oleh situasi yang TIDAK DAPAT DIGARANSI 100% OKE ketika program dijalankan (saat runtime)  An exception is an object that’s created when an error occurs in a Java program and Java can’t automatically fix the error.  The exception object contains information about the type of error that occurred.  Java Exception Hierarchy:

Handling Exception: Try-Catch We catch an exception by using a try-catch statement, which has this general form: try { // statements that can throw exceptions } catch (exception-type identifier) { // statements executed when exception is thrown }

Contoh Penanganan Exception pada kasus “Divide-by-Zero”: public class DivideByZero { public static void main(String[] args){ int a = 5; int b = 0;

// you know this won’t work

try { int c = a / b; // but you try it anyway } catch (ArithmeticException e){ System.out.println("Oops, you can’t divide by zero."); } } }

Catching All Exceptions If we have some code that might throw several different types of exceptions, and we want to provide specific processing for some but general processing for all the others, we can code the try statement as following: try { // statements that might throw several types of exceptions } catch (InputMismatchException e) { // statements that process InputMismatchException } catch (IOException e) { // statements that process IOException } catch (Exception e) { // statements that process all other exception types }

Finally  A finally block is a block that appears after all of the catch blocks for a statement.  It’s executed whether or not any exceptions are thrown by the try block or caught by any catch blocks.  The basic framework for a try statement with a finally block is this: try { // statements that can throw exceptions } catch (exception-type identifier){ // statements executed when exception is thrown } finally{ // statements that are executed // whether or not exceptions occur }

© Niko Ibrahim, S.Kom, MIT