Referensi Bahasa Pemrograman Java

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Yulia Hermanto
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1 Referensi Bahasa Pemrograman Java Tipe Data Primitif Type Bits Bytes Minimum Range Maximum Range byte or or short ,768 or ,767 or int ,147,483,648 or ,147,483,647 or long float E38 3.4E38 double E E308 char 16 2 n/a n/a boolean 8 1 n/a n/a Operator Aritmatika Operator Name # Operands Description + Addition 2 Add two operands - Subtraction 2 Subtract the right operand from the left * Multiplication 2 Multiplies the right operand and left operand / Division 2 Divides the right operand into the left operand % Modulus 2 Returns the value that is left over after dividing the right operand into the left operand ++ Increment 1 Adds 1 to the operand (x = x + 1) -- Decrement 1 Subtracts 1 from the operand (x = x -1) + Positive Sign 1 Promotes byte, short, and char types to the int type - Negative Sign 1 Changes a positive value to negative, and vice versa Karakter Khusus Sequence Character \n New line \t Tab \r Return \ Quotation Mark \\ Backslash

2 Assignment Operators Operator Name Description = Assignment Assigns a new value to the variable += Addition Adds the operand to the starting variable value of the variable and assigns the result to the variable -= Subtraction Subtracts the operand from the starting value of the variable and assigns the result to the variable *= Multiplication Multiplies the operand by the starting value of the variable and assigns the result to the variable /= Division Divides the operand by the starting value of the variable and assigns the result to the variable %= Modulus 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 Returns a true value if both operands are equals!= Inequality Returns a true value if the left and right operands are not equal > Greater Than Returns a true value if the left operand is greater than the right operand < Less Than Return a true value if the left operand is less than the right operand >= Greater Than Or Equal Returns a true value if the left operand is greater than or equal to the right operand <= Less Than or Equal 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 a && b true if both a and b are true OR a b true if either a or b (or both) is true ^ XOR a ^ b true if only a or b is true! NOT!a 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

3 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 next() or nextline() nextint() nextdouble() nextboolean() Description 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

4 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;

5 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

6 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);

7 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

8 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

9 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

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