Wetofu

Regex

• Sequence of character that forms a search pattern
• can be a single character, or a more complicated pattern
• can be used to perform all types of text search and text replace operation

package com.oop.regex;
// ebook hlm 510
public class Example1 {
public static void main(String[] args) {
String s1 = "Java";
// pattern matching : mencari ada tidaknya suatu string di dalam string lain 
System.out.println(s1+" equals Java : "+s1.equals("Java"));
System.out.println(s1+" matches Java : "+s1.matches("Java"));
// equals : parameter string
// matches : parameter regex (regular expression)
String regex1 = "J[a-z][a-z][a-z]";
String regex2 = "J[a-z]";
String regex3 = "j[a-z]";
System.out.println(s1+" matches "+regex1+": "+s1.matches(regex1));
System.out.println(s1+" matches "+regex2+": "+s1.matches(regex2));
System.out.println(s1+" matches "+regex3+": "+s1.matches(regex3));
/
        
        [a-z] : A single lowercase letter that is a, b, c, d, ... or z
        J[a-z][a-z][a-z] : A string that consists of four characters. 
        The first character is J.The second character is a, b, c, d, ... or z
        J[a-z] : Same as above, * means matches 0 or more occurrences of the preceding expression
        
        */
String s2 = "3";
String regex4 = "[0123]";
System.out.println(s2+" matches "+regex4+": "+s2.matches(regex4));
// [0123] : A single digit 0, 1, 2, or 3
}
}

• group parts of regex
• using round brackets ()
• $ you can refer to a group.
• $1 is the first group
• $2 is the second group

package com.oop.regex;
public class Example2 {
public static void main(String[] args) {
// formatting phone number
// mobile phone number, separate each 4 digits
String regex = "\b(\d{4})(\d{4})(\d{4})\b";
String replacementText = "$1-$2-$3";
System.out.println("085645123123".replaceAll(regex, replacementText));
// office phone number, separate between code area and phone number
regex = "\b(\d{1})(\d{3})(\d{6})\b";
replacementText = "(+62$2)-$3";
System.out.println("0271646999".replaceAll(regex, replacementText));
}
}

package com.oop.regex;

public class Example3 {
    public static void main(String[] args) {
        String EXAMPLE_TEST = "This is my small example "
                + "string which I'm going to " + "use for pattern matching.";
        
// matches word character [a-zA-Z_0-9]
        System.out.println(EXAMPLE_TEST.matches("\\w.*"));
        
// split based on whitespace character [ \t\n\x0b\r\f]
        String[] splitString = (EXAMPLE_TEST.split("\\s+"));
        System.out.println(splitString.length);// should be 14
        for (String string : splitString) {
            System.out.println(string);
        }

// replace all whitespace with tabs
        System.out.println(EXAMPLE_TEST.replaceAll("\\s+", "\t"));
    }
}

Pattern and Matcher :

• Advanced regular expressions
• java.util.regex
• create a pattern object which defines the regular expression
• pattern object allows to create a matcher object for a given string
• matcher object then allows to do regex operations on a string

package com.oop.regex;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Example4 {
public static void main(String[] args) {
String EXAMPLE_TEST = "This is my small example string which I'm going to use "
+ "for pattern matching.";
Pattern pattern = Pattern.compile("\w+");
// in case you would like to ignore case sensitivity,
// you could use this statement:
// Pattern pattern = Pattern.compile("\s+", Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(EXAMPLE_TEST);
// check all occurance
while (matcher.find()) {
System.out.print("Start index: " + matcher.start());
System.out.print(", End index: " + matcher.end() + " --> ");
System.out.println(matcher.group());
}
// now create a new pattern and matcher to replace whitespace with tabs
Pattern replace = Pattern.compile("\s+");
Matcher matcher2 = replace.matcher(EXAMPLE_TEST);
System.out.println(matcher2.replaceAll("\t"));
}
}

Praktikum 7 :

// Tugas praktikum 7

// Tulis sebuah program Java dengan input NIM mahasiswa FMIPA UNS
// Gunakan regular expression untuk mengekstrak asal program studi dan tahun angkatan mahasiswa berdasarkan NIM yang diinputkan!

// Misal

// M0120001 -> Matematika angkatan 2020 
// M0220001 -> Fisika angkatan 2020
// M0317001 -> Kimia angkatan 2017
// M0418001 -> Biologi angkatan 2018
// M0519001 -> Informatika angkatan 2019
// M0616001 -> Farmasi angkatan 2016
// M0719001 -> Statistika angkatan 2019
// M0819001 -> Ilmu Lingkungan angkatan 2019
// G0017075 -> Bukan mahasiswa FMIPA UNS

public class Prak7 {

	public static void cek_jurusan(String nim){
		
		if (nim.matches("M01[0-9]{6,6}")){
			System.out.println("Matematika angkatan "+ "20"+nim.substring(3,5));
		}
		else if (nim.matches("M02[0-9]{5,5}")){
			System.out.println("Fisika angkatan "+ "20"+nim.substring(3,5));
		}
		else if (nim.matches("M03[0-9]{5,5}")){
			System.out.println("Kimia angkatan "+ "20"+nim.substring(3,5));
		}
		else if (nim.matches("M04[0-9]{5,5}")){
			System.out.println("Biologi angkatan "+ "20"+nim.substring(3,5));
		}
		else if (nim.matches("M05[0-9]{5,5}")){
			System.out.println("Informatika angkatan "+ "20"+nim.substring(3,5));
		}
		else if (nim.matches("M06[0-9]{5,5}")){
			System.out.println("Farmasi angkatan "+ "20"+nim.substring(3,5));
		}
		else if (nim.matches("M07[0-9]{5,5}")){
			System.out.println("Statistika angkatan "+ "20"+nim.substring(3,5));
		}
		else if (nim.matches("M08[0-9]{5,5}")){
			System.out.println("Ilmu Lingkungan angkatan "+ "20"+nim.substring(3,5));
		}
		else {
			System.out.println("Bukan angkatan  mahasiswa FMIPA UNS");
		}
	}  
	public static void main(String[] args) {

		String nim = "M0519064";

		cek_jurusan(nim);

  }
}