Large Class
Penjelasan Smell
Smell ini terjadi ketika ada sebuah class yang memiliki terlalu banyak method dan/atau line of code.
Code yang mengandung Large Class berpotensi melanggar Single Responsibility Principle bila terdapat terlalu banyak jenis tanggungjawab yang dilakukan oleh satu class. Bila Large Class disertai dengan pelanggaran SRP, maka terjadi juga smell Divergent Change.
Pada contoh SemesterMenu.java, class ini bukan hanya berurusan dengan menu dan input console untuk CRUD semester saja. Class ini juga pegang kendali untuk pembuatan vector semester. Class ini juga terbebani dengan banyaknya variasi cara input di method getDateInput, getIntInput, dan getStringInput.
java
package fowler.bloaters.large_class.before;
import java.util.Date;
import java.text.SimpleDateFormat;
import java.util.Scanner;
import java.util.Vector;
public class SemesterMenu {
private Vector<Semester> semesters;
private Scanner scan;
public SemesterMenu() {
semesters = new Vector<Semester>();
scan = new Scanner(System.in);
}
public void open() {
while(menu()) {}
}
private boolean menu(){
showSemesters();
int input = printAndGetMenu();
switch(input){
case 1: create(); break;
case 2: delete(); break;
case 3: return false;
}
return true;
}
private void create() {
String label;
do {
label = getStringInput("Input label", 3, 20);
} while(!isLabelUnique(label));
Date startDate, endDate;
do {
startDate = getDateInput("Input start date", "yyyy-MM-dd");
endDate = getDateInput("Input end date", "yyyy-MM-dd");
} while(startDate.after(endDate));
semesters.add(new Semester(label, startDate, endDate));
}
private boolean isLabelUnique(String label) {
for(Semester s : semesters) {
if(s.getLabel().equalsIgnoreCase(label)) return false;
}
return true;
}
private void delete() {
int input = getIntInput("Choose semester", 1, semesters.size());
semesters.removeElementAt(input-1);
}
private int printAndGetMenu() {
System.out.println("1. Create");
System.out.println("2. Delete");
System.out.println("3. Exit");
return getIntInput("input menu", 1, 3);
}
private void showSemesters() {
for(int i = 0; i < semesters.size(); i++) {
Semester s = semesters.elementAt(i);
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
System.out.print((i+1) + ". ");
showSemester(s, format);
System.out.println("");
}
System.out.println("");
}
private void showSemester(Semester s, SimpleDateFormat format) {
System.out.print(s.getLabel());
System.out.print(" - ");
System.out.print(format.format(s.getStart()));
System.out.print(" - ");
System.out.print(format.format(s.getEnd()));
}
private Date getDateInput(String message, String format) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
sdf.setLenient(false);
Date date = null;
do {
try {
System.out.print(message + " ["+format+"]: ");
String input = scan.nextLine().trim();
date = sdf.parse(input);
} catch (Exception e) {
date = null;
}
} while(date == null);
return date;
}
private int getIntInput(String message, int min, int max) {
int input;
do{
System.out.print(message + " ["+min+"-"+max+"]: ");
try {
input = scan.nextInt();
} catch (Exception e) {
input = 0;
} finally {
scan.nextLine();
}
}while(input < min || input > max);
return input;
}
private String getStringInput(String message, int min, int max) {
String input;
do{
System.out.print(message + " ["+min+"-"+max+" chars]: ");
input = scan.nextLine().trim();
}while(input.length() < min || input.length() > max);
return input;
}
}package fowler.bloaters.large_class.before;
import java.util.Date;
import java.text.SimpleDateFormat;
import java.util.Scanner;
import java.util.Vector;
public class SemesterMenu {
private Vector<Semester> semesters;
private Scanner scan;
public SemesterMenu() {
semesters = new Vector<Semester>();
scan = new Scanner(System.in);
}
public void open() {
while(menu()) {}
}
private boolean menu(){
showSemesters();
int input = printAndGetMenu();
switch(input){
case 1: create(); break;
case 2: delete(); break;
case 3: return false;
}
return true;
}
private void create() {
String label;
do {
label = getStringInput("Input label", 3, 20);
} while(!isLabelUnique(label));
Date startDate, endDate;
do {
startDate = getDateInput("Input start date", "yyyy-MM-dd");
endDate = getDateInput("Input end date", "yyyy-MM-dd");
} while(startDate.after(endDate));
semesters.add(new Semester(label, startDate, endDate));
}
private boolean isLabelUnique(String label) {
for(Semester s : semesters) {
if(s.getLabel().equalsIgnoreCase(label)) return false;
}
return true;
}
private void delete() {
int input = getIntInput("Choose semester", 1, semesters.size());
semesters.removeElementAt(input-1);
}
private int printAndGetMenu() {
System.out.println("1. Create");
System.out.println("2. Delete");
System.out.println("3. Exit");
return getIntInput("input menu", 1, 3);
}
private void showSemesters() {
for(int i = 0; i < semesters.size(); i++) {
Semester s = semesters.elementAt(i);
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
System.out.print((i+1) + ". ");
showSemester(s, format);
System.out.println("");
}
System.out.println("");
}
private void showSemester(Semester s, SimpleDateFormat format) {
System.out.print(s.getLabel());
System.out.print(" - ");
System.out.print(format.format(s.getStart()));
System.out.print(" - ");
System.out.print(format.format(s.getEnd()));
}
private Date getDateInput(String message, String format) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
sdf.setLenient(false);
Date date = null;
do {
try {
System.out.print(message + " ["+format+"]: ");
String input = scan.nextLine().trim();
date = sdf.parse(input);
} catch (Exception e) {
date = null;
}
} while(date == null);
return date;
}
private int getIntInput(String message, int min, int max) {
int input;
do{
System.out.print(message + " ["+min+"-"+max+"]: ");
try {
input = scan.nextInt();
} catch (Exception e) {
input = 0;
} finally {
scan.nextLine();
}
}while(input < min || input > max);
return input;
}
private String getStringInput(String message, int min, int max) {
String input;
do{
System.out.print(message + " ["+min+"-"+max+" chars]: ");
input = scan.nextLine().trim();
}while(input.length() < min || input.length() > max);
return input;
}
}java
package fowler.bloaters.large_class.before;
public class Main {
public static void main(String[] args) {
new Main();
}
public Main() {
SemesterMenu semesterMenu = new SemesterMenu();
semesterMenu.open();
}
}package fowler.bloaters.large_class.before;
public class Main {
public static void main(String[] args) {
new Main();
}
public Main() {
SemesterMenu semesterMenu = new SemesterMenu();
semesterMenu.open();
}
}java
package fowler.bloaters.large_class.before;
import java.util.Date;
public class Semester {
private String label;
private Date start;
private Date end;
public Semester(String label, Date start, Date end) {
super();
this.label = label;
this.start = start;
this.end = end;
}
public String getLabel() {
return label;
}
public Date getStart() {
return start;
}
public Date getEnd() {
return end;
}
}package fowler.bloaters.large_class.before;
import java.util.Date;
public class Semester {
private String label;
private Date start;
private Date end;
public Semester(String label, Date start, Date end) {
super();
this.label = label;
this.start = start;
this.end = end;
}
public String getLabel() {
return label;
}
public Date getStart() {
return start;
}
public Date getEnd() {
return end;
}
}Penyelesaian
Dilakukan Extract Class pada:
- vector Semester dan validasi-validasinya diekstrak ke class baru bernama
Semesters. - fungsi
getDateInput,getIntInput, dangetStringInputdibuat menjadi 3 class yang terpisah. Lalu Extract Superclass menjadi abstract class Console.
Dilakukan Move Method pada:
- fungsi
showSemestermenjaditoStringdi class Semester. - fungsi
showSemestersmenjadishowdi class Semesters. - fungsi
isLabelUniquepindah ke class Semesters.
java
public class SemesterMenu {
private Semesters semesters;
public SemesterMenu(Semesters s) {
semesters = s;
}
public void open() {
while(menu()) {}
}
private boolean menu(){
semesters.show();
int input = printAndGetMenu();
switch(input){
case 1: create(); break;
case 2: delete(); break;
case 3: return false;
}
return true;
}
private int printAndGetMenu() {
System.out.println("1. Create");
System.out.println("2. Delete");
System.out.println("3. Exit");
return new IntInputter("input menu", 1, 3).get();
}
private void create() {
String label;
do {
label = new StringInputter("Input label", 3, 20).get();
} while(!semesters.isLabelUnique(label));
Date startDate, endDate;
do {
startDate = new DateInputter("Input start date", "yyyy-MM-dd").get();
endDate = new DateInputter("Input end date", "yyyy-MM-dd").get();
} while(startDate.after(endDate));
semesters.add(new Semester(label, startDate, endDate));
}
private void delete() {
int input = new IntInputter("Choose semester", 1, semesters.size()).get();
semesters.removeAtIndex(input-1);
}
}public class SemesterMenu {
private Semesters semesters;
public SemesterMenu(Semesters s) {
semesters = s;
}
public void open() {
while(menu()) {}
}
private boolean menu(){
semesters.show();
int input = printAndGetMenu();
switch(input){
case 1: create(); break;
case 2: delete(); break;
case 3: return false;
}
return true;
}
private int printAndGetMenu() {
System.out.println("1. Create");
System.out.println("2. Delete");
System.out.println("3. Exit");
return new IntInputter("input menu", 1, 3).get();
}
private void create() {
String label;
do {
label = new StringInputter("Input label", 3, 20).get();
} while(!semesters.isLabelUnique(label));
Date startDate, endDate;
do {
startDate = new DateInputter("Input start date", "yyyy-MM-dd").get();
endDate = new DateInputter("Input end date", "yyyy-MM-dd").get();
} while(startDate.after(endDate));
semesters.add(new Semester(label, startDate, endDate));
}
private void delete() {
int input = new IntInputter("Choose semester", 1, semesters.size()).get();
semesters.removeAtIndex(input-1);
}
}java
public class Main {
public static void main(String[] args) {
Semesters s = new Semesters();
new Main(s);
}
public Main(Semesters s) {
SemesterMenu semesterMenu = new SemesterMenu(s);
semesterMenu.open();
}
}public class Main {
public static void main(String[] args) {
Semesters s = new Semesters();
new Main(s);
}
public Main(Semesters s) {
SemesterMenu semesterMenu = new SemesterMenu(s);
semesterMenu.open();
}
}java
public class Semester {
private String label;
private Date start;
private Date end;
public Semester(String label, Date start, Date end) {
if(start.after(end)) {
throw new IllegalArgumentException("start date must before end date");
}
this.label = label;
this.start = start;
this.end = end;
}
public String getLabel() {
return label;
}
public Date getStart() {
return start;
}
public Date getEnd() {
return end;
}
@Override
public String toString() {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
return label + " - " + format.format(start) + " - " + format.format(end);
}
}public class Semester {
private String label;
private Date start;
private Date end;
public Semester(String label, Date start, Date end) {
if(start.after(end)) {
throw new IllegalArgumentException("start date must before end date");
}
this.label = label;
this.start = start;
this.end = end;
}
public String getLabel() {
return label;
}
public Date getStart() {
return start;
}
public Date getEnd() {
return end;
}
@Override
public String toString() {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
return label + " - " + format.format(start) + " - " + format.format(end);
}
}java
public class Semesters {
private Vector<Semester> semesters;
public Semesters() {
this.semesters = new Vector<Semester>();
}
public boolean add(Semester s) {
if(!isLabelUnique(s.getLabel())) {
throw new IllegalArgumentException("label must be unique");
}
return semesters.add(s);
}
public int size() {
return semesters.size();
}
public void removeAtIndex(int idx) {
semesters.removeElementAt(idx);
}
public void show() {
for(int i = 0; i < semesters.size(); i++) {
Semester s = semesters.elementAt(i);
System.out.println((i+1) + ". " + s.toString());
}
System.out.println("");
}
public boolean isLabelUnique(String label) {
for(Semester s : semesters) {
if(s.getLabel().equalsIgnoreCase(label)) return false;
}
return true;
}
}public class Semesters {
private Vector<Semester> semesters;
public Semesters() {
this.semesters = new Vector<Semester>();
}
public boolean add(Semester s) {
if(!isLabelUnique(s.getLabel())) {
throw new IllegalArgumentException("label must be unique");
}
return semesters.add(s);
}
public int size() {
return semesters.size();
}
public void removeAtIndex(int idx) {
semesters.removeElementAt(idx);
}
public void show() {
for(int i = 0; i < semesters.size(); i++) {
Semester s = semesters.elementAt(i);
System.out.println((i+1) + ". " + s.toString());
}
System.out.println("");
}
public boolean isLabelUnique(String label) {
for(Semester s : semesters) {
if(s.getLabel().equalsIgnoreCase(label)) return false;
}
return true;
}
}Lihat hasilnya di package after.