Kilka dodatkowych przykładów

PC22-ZaawansowaneElementyJavy/src/main/java/emps/comparable/Employee.java

+package emps.comparable;
+
+import java.time.LocalDate;
+import java.util.Objects;
+
+public class Employee implements Comparable<Employee> {
+	private int id;
+	private String firstName;
+	private String lastName;
+	private String jobTitle;
+	private double salary;
+	private LocalDate hireDate;
+	private String departmentName;
+	private String streetAddress;
+	private String postalCode;
+	private String city;
+	private String country;
+
+	public Employee(int id, String firstName, String lastName, String jobTitle, double salary, LocalDate hireDate,
+			String departmentName, String streetAddress, String postalCode, String city, String country) {
+		this.id = id;
+		this.firstName = firstName;
+		this.lastName = lastName;
+		this.jobTitle = jobTitle;
+		this.salary = salary;
+		this.hireDate = hireDate;
+		this.departmentName = departmentName;
+		this.streetAddress = streetAddress;
+		this.postalCode = postalCode;
+		this.city = city;
+		this.country = country;
+	}
+
+	public int getId() {
+		return id;
+	}
+
+	public void setId(int id) {
+		this.id = id;
+	}
+
+	public String getFirstName() {
+		return firstName;
+	}
+
+	public void setFirstName(String firstName) {
+		this.firstName = firstName;
+	}
+
+	public String getLastName() {
+		return lastName;
+	}
+
+	public void setLastName(String lastName) {
+		this.lastName = lastName;
+	}
+
+	public String getJobTitle() {
+		return jobTitle;
+	}
+
+	public void setJobTitle(String jobTitle) {
+		this.jobTitle = jobTitle;
+	}
+
+	public double getSalary() {
+		return salary;
+	}
+
+	public void setSalary(double salary) {
+		this.salary = salary;
+	}
+
+	public LocalDate getHireDate() {
+		return hireDate;
+	}
+
+	public void setHireDate(LocalDate hireDate) {
+		this.hireDate = hireDate;
+	}
+
+	public String getDepartmentName() {
+		return departmentName;
+	}
+
+	public void setDepartmentName(String departmentName) {
+		this.departmentName = departmentName;
+	}
+
+	public String getStreetAddress() {
+		return streetAddress;
+	}
+
+	public void setStreetAddress(String streetAddress) {
+		this.streetAddress = streetAddress;
+	}
+
+	public String getPostalCode() {
+		return postalCode;
+	}
+
+	public void setPostalCode(String postalCode) {
+		this.postalCode = postalCode;
+	}
+
+	public String getCity() {
+		return city;
+	}
+
+	public void setCity(String city) {
+		this.city = city;
+	}
+
+	public String getCountry() {
+		return country;
+	}
+
+	public void setCountry(String country) {
+		this.country = country;
+	}
+
+	@Override
+	public String toString() {
+		return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", jobTitle=" + jobTitle
+				+ ", salary=" + salary + ", hireDate=" + hireDate + ", departmentName=" + departmentName
+				+ ", streetAddress=" + streetAddress + ", postalCode=" + postalCode + ", city=" + city + ", country="
+				+ country + "]";
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(city, country, departmentName, firstName, hireDate, id, jobTitle, lastName, postalCode,
+				salary, streetAddress);
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj)
+			return true;
+		if (obj == null)
+			return false;
+		if (getClass() != obj.getClass())
+			return false;
+		Employee other = (Employee) obj;
+		return Objects.equals(city, other.city) && Objects.equals(country, other.country)
+				&& Objects.equals(departmentName, other.departmentName) && Objects.equals(firstName, other.firstName)
+				&& Objects.equals(hireDate, other.hireDate) && id == other.id
+				&& Objects.equals(jobTitle, other.jobTitle) && Objects.equals(lastName, other.lastName)
+				&& Objects.equals(postalCode, other.postalCode)
+				&& Double.doubleToLongBits(salary) == Double.doubleToLongBits(other.salary)
+				&& Objects.equals(streetAddress, other.streetAddress);
+	}
+
+	@Override
+	public int compareTo(Employee other) {
+		// Metoda compareTo (i analogicznie compare w interfejsice Comparator)
+		// ma zwrócić wartość ujemną, jeśli lewy obiekt (tutaj this) jest mniejszy od prawego
+		// ma zwrócić wartość dodatnią, jeśli lewy obiekt jest większy od prawego
+		// ma zwrócić 0, jeśli oba obiekty są równe.
+		
+		// To my, jako autorzy, decydujemy co to znaczy mniejszy/większy.
+		// W tej wersji porównujemy pensje pracowników. Aby było łatwo i poprawnie, korzystamy z gotowej metody
+		return Double.compare(this.salary, other.salary);
+	}
+	
+	// Interfejs Comparable i metoda compareTo → domyślny sposób porównywania wpisany w definicję klasy, tzw. "natural order"
+	// Interfejs Comparator i metoda compare → dodatkowy, alternatywny sposób porównywania tworzony poza klasą, której dotyczy.
+	// "Maszykna porównująca obiekty", czyli taka "waga".
+}

PC22-ZaawansowaneElementyJavy/src/main/java/emps/comparable/ObslugaCSV.java

+package emps.comparable;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.time.LocalDate;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Scanner;
+
+// To jest przykład tzw. klasy narzędziowej (utility class),
+// w której są zdefiniowane różne funkcje - w formie metod statycznych.
+
+public class ObslugaCSV {
+
+	public static List<Employee> wczytaj(File plik) {
+		List<Employee> lista = Collections.synchronizedList(new ArrayList<>());
+		try (Scanner scanner = new Scanner(plik)) {
+			scanner.nextLine();
+			while(scanner.hasNextLine()) {
+				String linia = scanner.nextLine();
+				String[] t = linia.split(";", 11);
+				
+				Employee emp = new Employee(Integer.parseInt(t[0]),
+						t[1], t[2], t[3], Double.parseDouble(t[4]), LocalDate.parse(t[5]),
+						t[6], t[7], t[8], t[9], t[10]);
+				lista.add(emp);
+			}
+		} catch (FileNotFoundException e) {
+			e.printStackTrace();
+		}
+		
+		return lista;
+	}
+	
+	public static List<Employee> wczytaj(String sciezka) {
+		return wczytaj(new File(sciezka));
+	}
+}

PC22-ZaawansowaneElementyJavy/src/main/java/emps/comparable/Porownywanie.java

+package emps.comparable;
+
+import java.text.Collator;
+import java.util.List;
+
+public class Porownywanie {
+
+	public static void main(String[] args) {
+		List<Employee> emps = ObslugaCSV.wczytaj("emps.csv");
+		
+		Employee emp110 = emps.get(10);
+		Employee emp120 = emps.get(20);
+		
+		System.out.println(emp110);
+		System.out.println(emp120);
+		System.out.println();
+		
+		// w Javie nie działa porównywanie za pomocą < > rzeczy innych niż liczby
+//		if(emp110 < emp120) {
+//			System.out.println("110 zarabia mniej");
+//		} else if(emp110 > emp120) {
+//			System.out.println("110 zarabia więcej");
+//		} else {
+//			System.out.println("zarabiają tyle samo");
+//		}
+		
+		// zamiast tego, jeśli klasa jest Comparable, to wynik operacji compareTo porównujemy z zerem
+		
+		if(emp110.compareTo(emp120) < 0) {
+			System.out.println("110 zarabia mniej");
+		} else if(emp110.compareTo(emp120) > 0) {
+			System.out.println("110 zarabia więcej");
+		} else {
+			System.out.println("zarabiają tyle samo");
+		}
+		// to samo dla klas takich jak String, BigDecimal, LocalDate
+		
+		String ala = "Ala";
+		String ola = "Ola";
+		System.out.println(ala.compareTo(ola));
+		if(ala.compareTo(ola) < 0) {
+			System.out.println("Ala < Ola");
+		}
+		System.out.println();
+		
+		System.out.println("Łukasz".compareTo("Marek")); // >
+		
+		Collator collator = Collator.getInstance();
+		System.out.println(collator.compare("Łukasz", "Marek")); // <
+	}
+
+}

PC22-ZaawansowaneElementyJavy/src/main/java/emps/comparable/Sortowanie_Lista.java

+package emps.comparable;
+
+import java.util.List;
+
+public class Sortowanie_Lista {
+	public static void main(String[] args) {
+		List<Employee> emps = ObslugaCSV.wczytaj("emps.csv");
+		
+		emps.sort(null);
+		
+		for (Employee emp : emps) {
+			System.out.println(emp);
+		}
+		
+	}
+}
\ No newline at end of file

PC22-ZaawansowaneElementyJavy/src/main/java/emps/comparable/Sortowanie_Stream.java

+package emps.comparable;
+
+import java.util.List;
+
+public class Sortowanie_Stream {
+	public static void main(String[] args) {
+		List<Employee> emps = ObslugaCSV.wczytaj("emps.csv");
+		
+		emps.stream()
+				.sorted()
+				.forEachOrdered(emp -> System.out.printf("%s %s (%s) zarabia %.2f\n",
+						emp.getFirstName(), emp.getLastName(), emp.getJobTitle(), emp.getSalary()));
+		
+	}
+}
\ No newline at end of file

PC22-ZaawansowaneElementyJavy/src/main/java/emps/strumieniowo/P2_FiltrowanieDoListyEmp.java

+package emps.strumieniowo;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class P2_FiltrowanieDoListyEmp {
+
+	public static void main(String[] args) {
+		List<Employee> emps = ObslugaCSV.wczytaj("emps.csv");
+
+		List<Employee> wyniki = emps.stream()
+				.filter(emp -> emp.getSalary() >= 10_000)
+				.collect(Collectors.toList());
+		
+		wyniki.forEach(System.out::println);
+	}
+
+}

PC22-ZaawansowaneElementyJavy/src/main/java/emps/strumieniowo/P2_FiltrowanieDoListyString.java

+package emps.strumieniowo;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class P2_FiltrowanieDoListyString {
+
+	public static void main(String[] args) {
+		List<Employee> emps = ObslugaCSV.wczytaj("emps.csv");
+
+		List<String> wyniki = emps.stream()
+				.filter(emp -> emp.getSalary() >= 10_000)
+				.map(emp -> String.format("Pracownik %s %s (%s) zarabia %.2f USD",
+						emp.getFirstName(), emp.getLastName(), emp.getJobTitle(), emp.getSalary()))
+				.collect(Collectors.toList());
+		
+		wyniki.forEach(System.out::println);
+	}
+
+}

PC22-ZaawansowaneElementyJavy/src/main/java/emps/strumieniowo/P6_UnikalneMiasta_Set.java

+package emps.strumieniowo;
+
+import java.util.List;
+
+public class P6_UnikalneMiasta_Set {
+
+	public static void main(String[] args) {
+		List<Employee> emps = ObslugaCSV.wczytaj("emps.csv");
+		
+		emps.stream()
+				.map(Employee::getCity)
+				.distinct()
+				.forEach(System.out::println);
+	}
+
+}