Referensi Bahasa Pemrograman Java
Tipe Data Primitif
Type Bits Bytes Minimum Range Maximum Range
byte 8 1 -128 or -27 127 or 27-1
short 16 2 -32,768 or -215 32,767 or 215-1
int 32 4 -2,147,483,648 or -231 2,147,483,647 or 231-1
long 64 8 -263 263-1
float 32 4 -3.4E38 3.4E38
double 64 8 -1.7E308 1.7E308
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 \\ BackslashAssignment 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 +
“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() Reads a String value from the user
nextInt() Reads an integer value from the user
nextDouble() Reads a double 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
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 }
