Strings And Arrays
Strings
Tipe data String (java.lang.String) merupakan rangkaian/gabungan dari sejumlah karakter/text yang diinisialisasikan menggunakan double quote (" ")
public class StringDemo {
public static void main (String[] args) {
String greeting = "Hello World";
System.out.println(greeting);
}
}String Length
public class StringDemo {
public static void main (String[] args) {
String greeting = "Hello World";
int len = greeting.length();
System.out.println("String length is " + len);
}
}Concatenating String
public class StringDemo {
public static void main (String[] args) {
String greeting = "Hello ";
String str1 = greeting.concat("World");
String str2 = greeting + "World";
System.out.println(str1);
System.out.println(str2);
}
}public class StringDemo {
public static void main (String[] args) {
String sentence = "Java is my favorite language programming";
// Guess which methods to solve these:
// Find out if this sentence contains the word "Java"
sentence.yourMethodHere("Java");
// Find out the index of "f" in this sentence
sentence.yourMethodHere("f");
// Find out if this sentence begins with the word "Java"
sentence.yourMethodHere("Java");
// Find out if this sentence ends with the word "programming"
sentence.yourMethodHere("programming");
// convert the sentence to lowercase
sentence.yourMethodHere();
// convert the sentence to uppercase
sentence.yourMethodHere();
}
}More String Methods (1)
public class StringDemo {
public static void main (String[] args) {
String sentence = "Java is my favorite language programming";
// Guess which methods to solve these:
// Find out if this sentence contains the word "Java"
sentence.contains("Java");
// Find out the index of "f" in this sentence
sentence.indexOf("f");
// Find out if this sentence begins with the word "Java"
sentence.startsWith("Java");
// Find out if this sentence ends with the word "programming"
sentence.endsWith("programming");
// convert the sentence to lowercase
sentence.toLowerCase();
// convert the sentence to uppercase
sentence.toUpperCase();
}
}More String Methods (2)
Converting Strings to Numbers
public class ConvertingStringToNumber {
public static void main(String[] args) {
String number = "10";
int result1 = Integer.parseInt(number);
int result2 = Integer.valueOf(number);
System.out.println(result1);
System.out.println(result2);
String anotherNumber = "10A";
int result = Integer.parseInt(anotherNumber);
System.out.println(result); // NumberFormatException
}
}Converting Numbers to Strings
public class ConvertingNumberToString {
public static void main(String[] args) {
int number = 10;
String result1 = Integer.toString(number);
String result2 = String.valueOf(number);
System.out.println(result1);
System.out.println(result2);
}
}Arrays
Arrays (java.util.Arrays) merupakan container object yang dapat menyimpan banyak data dalam satu variabel.
Pada pemrograman java, array hanya bisa menyimpan data yang bertipe sama.
Setiap item di dalam array disebut elemen dan setiap elemen memiliki index yang dimulai dari 0
Creating and Initializing (1)
public class ArrayDemo {
public static void main(String[] args) {
// declares an array of integers and
// allocates memory for 5 integers
int[] numbers = new int[5];
numbers[0] = 100; // initialize first element
numbers[1] = 200; // initialize second element
numbers[2] = 300;
numbers[3] = 400;
numbers[4] = 500;
// another declares an array of integers and initialize
int[] anotherExample = { 100, 200, 300, 400, 500 };
System.out.println("Element at index 0: " + numbers[0]);
System.out.println("Element at index 1: " + numbers[1]);
System.out.println("Element at index 2: " + numbers[2]);
System.out.println("Element at index 3: " + numbers[3]);
System.out.println("Element at index 4: " + numbers[4]);
}
}Creating and Initializing (2)
class MultiDimArrayDemo {
public static void main(String[] args) {
String[][] contats = {
{"Nur","08111"},
{"Ratna","08522"},
{"Sari","08122"}
};
}
}| "Nur" | "08111" |
|---|---|
| "Ratna" | "08522" |
| "Sari" | "08122" |
| 0 | 1 |
|---|
| 0 |
|---|
| 1 |
| 2 |
contats[0][0]
contats[2][1]
Exercise (1)
Pisahkan kalimat ini menjadi beberapa kata
public class Exercise1 {
public static void main (String[] args) {
String sentence = "Java is my favorite language programming";
// Word-1: Java
// Word-2: is
// Word-3: my
// Word-4: favorite
// Word-5: language
// Word-6: programming
// clue: pisahkan berdasarkan spasi
}
}Exercise (2)
Ganti setiap huruf "a" menjadi "i"
public class Exercise2 {
public static void main (String[] args) {
String sentence = "Java is my favorite language programming";
// Original: Java is my favorite language programming
// Modified: Jivi is my fivorite linguige progrimming
}
}Exercise (3)
Ubahlah String berikut menjadi kumpulan karakter yang disimpan di Array
public class Exercise {
public static void main (String[] args) {
String sentence = "java programming";
char[] letters;
// Letter-1: j == letters[0]
// Letter-2: a == letters[1]
// ....
// Letter-16: g == letters[15]
}
}Exercise (4)
Cetak kata berikut berdasarkan kalimat
"Java Programming"
a. ava c. program
b. va pro d. va programming
public class Exercise4 {
public static void main (String[] args) {
String sentence = "Java Programming";
// clue: gunakan method substring
}
}Exercise (5)
Carilah nilai minimum dan maksimum dari deretan bilangan berikut:
7, 23, 4, 67, -4, 4, 0, 100, 39, 42, 5, -2
public class Exercise5 {
public static void main (String[] args) {
int[] numbers = { 7, 23, 4, 67, -4,
4, 0, 100, 39, 42,
5, -2
};
// min: -4
// max: 100
}
}Solution
Exercise (1)
Pisahkan kalimat ini menjadi beberapa kata
public class Exercise1 {
public static void main (String[] args) {
String sentence = "Java is my favorite language programming";
String[] words;
words = sentence.split(" ");
for(int i = 0; i < words.length; i++) {
System.out.println("Word-" + (i + 1) + ": " + words[i]);
}
}
}Exercise (2)
Pisahkan kalimat ini menjadi beberapa kata
public class Exercise2 {
public static void main (String[] args) {
String sentence = "Java is my favorite language programming";
String modified;
String modified = sentence.replace("a", "i");
System.out.println("Original: " + sentence);
System.out.println("Modified: " + modified);
}
}Exercise (3)
Ubahlah String berikut menjadi kumpulan karakter yang disimpan di Array
public class Exercise3 {
public static void main (String[] args) {
Strings sentence = "java programming";
char[] letters;
letters = sentence.toCharArray();
System.out.println("Letter-1: " letters[0]);
System.out.println("Letter-2: " letters[1]);
System.out.println("Letter-3: " letters[2]);
System.out.println("Letter-16: " letters[15]);
for(int i = 0; i < letters.length; i++) {
System.out.println("Letter-" + (i + 1) + ": " letters[i]);
}
}
}Exercise (4)
Cetak kata berikut berdasarkan kalimat
"Java Programming"
a. ava c. program
b. va pro d. va programming
public class Exercise4 {
public static void main (String[] args) {
String sentence = "Java Programming";
sentence = sentence.toLowerCase();
System.out.println(sentence.substring(1, 4));
System.out.println(sentence.substring(2, 8));
System.out.println(sentence.substring(5, 12));
System.out.println(sentence.substring(2));
}
}Exercise (5)
Carilah nilai minimum dan maksimum dari deretan bilangan berikut:
import java.util.Arrays;
public class Exercise {
public static void main (String[] args) {
int[] numbers = { 7, 23, 4, 67, -4, 4, 0,
100, 39, 42, 5, -2
};
Arrays.sort(numbers);
int min = numbers[0];
int max = numbers[numbers.length-1];
System.out.println("Min: " + min);
System.out.println("Max: " + max);
}
}String And Array
By Nur Ratna Sari
