DEV Community: Vaniusca 23

Java methods and classes examples 2

Vaniusca 23 — Sat, 25 Jan 2025 18:03:00 +0000

What is a Class in Java? A class is a blueprint for creating objects. It defines attributes (variables) and methods (functions) that describe the behavior of an object.
Basic Syntax of a Class

`// defining a class
public class Car {
// attributes (variables)
String brand;
int speed;

// method (function)
void honk() {
System.out.println("Beep Beep!");
}
}`
📌 Explanation:

Car is a class.
brand and speed are attributes (also called instance variables).
honk() is a method (a function inside a class).

How to Create an Object? An object is an instance of a class. You create objects using the new keyword.
Creating an Object in Java

`public class Main {
public static void main(String[] args) {
// creating an object of the Car class
Car myCar = new Car();

// assigning values to attributes
myCar.brand = "Toyota";
myCar.speed = 120;

// calling a method
myCar.honk();

// printing attributes
System.out.println("Brand: " + myCar.brand);
System.out.println("Speed: " + myCar.speed + " km/h");

}
}`
🔹 Output:

makefile
Beep Beep!
Brand: Toyota
Speed: 120 km/h
📌 Explanation:

Car myCar = new Car(); → Creates an object named myCar.
myCar.brand = "Toyota"; → Assigns a value to brand.
myCar.honk(); → Calls the honk() method.

Constructors in Java A constructor is a special method that is automatically called when an object is created.
Example of a Constructor

`public class Car {
String brand;
int speed;

// constructor
public Car(String brand, int speed) {
this.brand = brand;
this.speed = speed;
}

// method to display car details
void displayCar() {
System.out.println("Brand: " + brand);
System.out.println("Speed: " + speed + " km/h");
}
}

public class Main {
public static void main(String[] args) {
// using constructor to initialize values
Car myCar = new Car("Honda", 150);
myCar.displayCar();
}
}`
🔹 Output:

Brand: Honda
Speed: 150 km/h
📌 Explanation:

The constructor Car(String brand, int speed) initializes attributes when the object is created.
The this keyword refers to the current object's instance.

Types of Methods in Java Java has two types of methods:
Instance Methods (work with object data)
Static Methods (belong to the class, not objects)
Example of Instance and Static Methods

`public class MathOperations {
// instance method
int square(int x) {
return x * x;
}

// static method
static int add(int a, int b) {
return a + b;
}
}

public class Main {
public static void main(String[] args) {
// calling an instance method
MathOperations math = new MathOperations();
int result = math.square(5);
System.out.println("Square: " + result);

// calling a static method
int sum = MathOperations.add(10, 20);
System.out.println("Sum: " + sum);

}
}`
🔹 Output:

Square: 25
Sum: 30
📌 Explanation:

square(int x) is an instance method, so we need to create an object (math.square(5);).
add(int a, int b) is a static method, so we can call it directly using the class name (MathOperations.add(10, 20);).

Method Overloading in Java Method Overloading allows multiple methods with the same name but different parameters.
Example of Method Overloading

`public class Calculator {
// method with two parameters
int add(int a, int b) {
return a + b;
}

// overloaded method with three parameters
int add(int a, int b, int c) {
return a + b + c;
}
}

public class Main {
public static void main(String[] args) {
Calculator calc = new Calculator();
System.out.println("Sum (2 numbers): " + calc.add(10, 20));
System.out.println("Sum (3 numbers): " + calc.add(10, 20, 30));
}
}`
🔹 Output:

Sum (2 numbers): 30
Sum (3 numbers): 60
📌 Explanation:

The method add() is overloaded (two versions with different numbers of parameters).
The compiler automatically selects the correct method.

Subiectul 3 - Masina

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public class Masina {
private int carId;
private String carMarca;
private int carService; // 0/1 = nu e / e în service
private double carVenit;
private double carCheltuiala;

// Constructor explicit
public Masina(int carId, String carMarca, int carService, double carVenit, double carCheltuiala) {
this.carId = carId;
this.carMarca = carMarca;
this.carService = carService;
this.carVenit = carVenit;
this.carCheltuiala = carCheltuiala;
}

// Geteri și seteri (id,marca,seevice,venit, cheltuiala)
public int getId() { return carId; }
public void setId(int carId) { this.carId = carId; }

public String getMarca() { return carMarca; }
public void setMarca(String carMarca) { this.carMarca = carMarca; }

public int getService() { return carService; }
public void setService(int carService) { this.carService = carService; }

public double getVenit() { return carVenit; }
public void addVenit(double suma) { this.carVenit += suma; }

public double getCheltuiala() { return carCheltuiala; }
public void addCheltuiala(double suma) { this.carCheltuiala += suma; }

// toString pentru informatii despre masina
@override
public String toString() {
return "Masina [ID=" + carId + ", Marca=" + carMarca + ", Service=" + (carService == 1 ? "DA" : "NU") +
", Venit=" + carVenit + ", Cheltuieli=" + carCheltuiala + "]";
}
}
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import java.awt.;
import java.awt.event.;
import java.util.ArrayList;

public class TihanIoan extends Frame {
private ArrayList masini = new ArrayList<>(); // Lista de masini
private List listMasini = new List(); // Listă pentru afișarea mașinilor
private Button btnAdaugaMasina = new Button("Adaugă Mașină"); // Buton pentru a deschide alt formular
public TihanIoan() {
// Setăm dereastra princ.
setTitle("Gestionare Mașini");
setSize(400, 300);
setLayout(new FlowLayout());
setVisible(true);

   //componente
   add(new Label("Lista Mașini:"));
   add(listMasini);
   add(btnAdaugaMasina);


   //deschiderea formularului
   btnAdaugaMasina.addActionListener(e -> new FormularAdaugareMasina());


   // inchidere principala
   addWindowListener(new WindowAdapter() {
       public void windowClosing(WindowEvent e) {
           dispose();
       }
   });

}

class FormularAdaugareMasina extends Frame {
private TextField txtId = new TextField(10);
private TextField txtMarca = new TextField(10);
private Button btnSalveaza = new Button("Salvează");
private Button btnAnuleaza = new Button("Anulează");

   public FormularAdaugareMasina() {
       // Setam adauga maisna
       setTitle("Adaugă Mașină");
       setSize(250, 200);
       setLayout(new FlowLayout());
       setVisible(true);


       // Adaugam componente pentru formular
       add(new Label("ID Mașină:"));
       add(txtId);
       add(new Label("Marca Mașinii:"));
       add(txtMarca);
       add(btnSalveaza);
       add(btnAnuleaza);


       // salvam masina
       btnSalveaza.addActionListener(e -> {
           try {
               int id = Integer.parseInt(txtId.getText());
               String marca = txtMarca.getText().trim();


               if (marca.isEmpty()) {
                   showMessage("Introduceți o marcă validă!");
                   return;
               }


               // adaugam maina noua
               Masina masina = new Masina(id, marca, 0, 0.0, 0.0);
               masini.add(masina);
               listMasini.add(marca); // Adăugăm marca în lista vizuală



               dispose();
           } catch (NumberFormatException ex) {
               showMessage("ID-ul trebuie să fie un număr!");
           }
       });


       // anulam
       btnAnuleaza.addActionListener(e -> dispose());


       addWindowListener(new WindowAdapter() {
           public void windowClosing(WindowEvent e) {
               dispose();
           }
       });
   }


   // mesaj de eroare
   private void showMessage(String message) {
       Dialog dialog = new Dialog(this, "Atenție", true);
       dialog.setLayout(new FlowLayout());
       dialog.add(new Label(message));
       Button btnOk = new Button("OK");
       btnOk.addActionListener(e -> dialog.setVisible(false));
       dialog.add(btnOk);
       dialog.setSize(200, 100);
       dialog.setVisible(true);
   }

}

// main-ul aplicatiei finale
public static void main(String[] args) {
new TihanIoan();
}
}
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import java.awt.;
import java.awt.event.;
import java.util.ArrayList;

public class TihanIoan extends Frame {
private ArrayList masini = new ArrayList<>();
private List listMasini = new List();

private TextField txtId = new TextField();
private TextField txtMarca = new TextField();
private TextField txtVenit = new TextField();
private TextField txtCheltuiala = new TextField();

private Button btnAdaugaMasina = new Button("Adauga o masina noua");
private Button btnAdaugaVenit = new Button("Adauga venit");
private Button btnAdaugaCheltuiala = new Button("Adauga cheltuiala");
private Button btnAfisare = new Button("Informatii actuale");

private Checkbox checkService = new Checkbox("Masina este in service");
private Label lblInfo = new Label("Informatii despre masina selectata");

public TihanIoan() {
setTitle("Gestionare Masini");
setSize(1300, 300);
setLayout(new FlowLayout());

   add(new Label("ID Masina:"));
   add(txtId);
   txtId.setColumns(10);


   add(new Label("Marca Masinii:"));
   add(txtMarca);
   txtMarca.setColumns(10);


   add(btnAdaugaMasina);
   add(listMasini);


   add(new Label("Suma Venit:"));
   add(txtVenit);
   txtVenit.setColumns(10);
   add(btnAdaugaVenit);


   add(new Label("Suma Cheltuială:"));
   add(txtCheltuiala);
   txtCheltuiala.setColumns(10);
   add(btnAdaugaCheltuiala);


   add(checkService);
   add(btnAfisare);
   add(lblInfo);


   // Eveniment adauga masina
   btnAdaugaMasina.addActionListener(e -> {
       try {
           int id = Integer.parseInt(txtId.getText());
           String marca = txtMarca.getText();
           Masina masina = new Masina(id, marca, 0, 0.0, 0.0);
           masini.add(masina);
           listMasini.add(marca);
       } catch (NumberFormatException ex) {
           showAlert("ID-ul trebuie să fie numar!!");
       }
   });


   // Eveniment adauga venit
   btnAdaugaVenit.addActionListener(e -> {
       int index = listMasini.getSelectedIndex();
       if (index != -1) {
           Masina masina = masini.get(index);
           if (masina.getService() == 0) {
               masina.addVenit(Double.parseDouble(txtVenit.getText()));
           } else {
               showAlert("Masina este in service! Nu poti adauga venituri.");
           }
       } else {
           showAlert("Selecteaza o masina!");
       }
   });


   // Eveniment adauga cheltuiala
   btnAdaugaCheltuiala.addActionListener(e -> {
       int index = listMasini.getSelectedIndex();
       if (index != -1) {
           Masina masina = masini.get(index);
           masina.addCheltuiala(Double.parseDouble(txtCheltuiala.getText()));
       } else {
           showAlert("Selecteaza o masina!");
       }
   });


   // Eveniment service
   listMasini.addItemListener(e -> {
       int index = listMasini.getSelectedIndex();
       if (index != -1) {
           Masina masina = masini.get(index);
           checkService.setState(masina.getService() == 1);
       }
   });


   checkService.addItemListener(e -> {
       int index = listMasini.getSelectedIndex();
       if (index != -1) {
           Masina masina = masini.get(index);
           masina.setService(checkService.getState() ? 1 : 0);
       }
   });


   // Buton pentru inforamtii
   btnAfisare.addActionListener(e -> {
       int index = listMasini.getSelectedIndex();
       if (index != -1) {
           Masina masina = masini.get(index);
           lblInfo.setText(masina.toString());
       } else {
           showAlert("Selecteaza o masina!");
       }
   });


   addWindowListener(new WindowAdapter() {
       public void windowClosing(WindowEvent e) {
           dispose();
       }
   });


   setVisible(true);

}

private void showAlert(String message) {
Dialog dialog = new Dialog(this, "Atentie", true);
dialog.setLayout(new FlowLayout());
dialog.add(new Label(message));
Button btnOk = new Button("OK");
btnOk.addActionListener(e -> dialog.setVisible(false));
dialog.add(btnOk);
dialog.setSize(350, 100);
dialog.setVisible(true);
}

public static void main(String[] args) {
new TihanIoan();
}
}

Java methods and classes examples 1

Vaniusca 23 — Sat, 25 Jan 2025 18:02:14 +0000

What is a Class in Java? A class is a blueprint for creating objects. It defines attributes (variables) and methods (functions) that describe the behavior of an object.
Basic Syntax of a Class

`// defining a class
public class Car {
// attributes (variables)
String brand;
int speed;

// method (function)
void honk() {
System.out.println("Beep Beep!");
}
}`
📌 Explanation:

Car is a class.
brand and speed are attributes (also called instance variables).
honk() is a method (a function inside a class).

How to Create an Object? An object is an instance of a class. You create objects using the new keyword.
Creating an Object in Java

`public class Main {
public static void main(String[] args) {
// creating an object of the Car class
Car myCar = new Car();

// assigning values to attributes
myCar.brand = "Toyota";
myCar.speed = 120;

// calling a method
myCar.honk();

// printing attributes
System.out.println("Brand: " + myCar.brand);
System.out.println("Speed: " + myCar.speed + " km/h");

}
}`
🔹 Output:

makefile
Beep Beep!
Brand: Toyota
Speed: 120 km/h
📌 Explanation:

Car myCar = new Car(); → Creates an object named myCar.
myCar.brand = "Toyota"; → Assigns a value to brand.
myCar.honk(); → Calls the honk() method.

Constructors in Java A constructor is a special method that is automatically called when an object is created.
Example of a Constructor

`public class Car {
String brand;
int speed;

// constructor
public Car(String brand, int speed) {
this.brand = brand;
this.speed = speed;
}

// method to display car details
void displayCar() {
System.out.println("Brand: " + brand);
System.out.println("Speed: " + speed + " km/h");
}
}

public class Main {
public static void main(String[] args) {
// using constructor to initialize values
Car myCar = new Car("Honda", 150);
myCar.displayCar();
}
}`
🔹 Output:

Brand: Honda
Speed: 150 km/h
📌 Explanation:

The constructor Car(String brand, int speed) initializes attributes when the object is created.
The this keyword refers to the current object's instance.

Types of Methods in Java Java has two types of methods:
Instance Methods (work with object data)
Static Methods (belong to the class, not objects)
Example of Instance and Static Methods

`public class MathOperations {
// instance method
int square(int x) {
return x * x;
}

// static method
static int add(int a, int b) {
return a + b;
}
}

// calling a static method
int sum = MathOperations.add(10, 20);
System.out.println("Sum: " + sum);

}
}`
🔹 Output:

Square: 25
Sum: 30
📌 Explanation:

Method Overloading in Java Method Overloading allows multiple methods with the same name but different parameters.
Example of Method Overloading

`public class Calculator {
// method with two parameters
int add(int a, int b) {
return a + b;
}

// overloaded method with three parameters
int add(int a, int b, int c) {
return a + b + c;
}
}

Sum (2 numbers): 30
Sum (3 numbers): 60
📌 Explanation:

The method add() is overloaded (two versions with different numbers of parameters).
The compiler automatically selects the correct method.

// clasa angajati
public class Angajati {
private String angNume; // nume angajat
private double tarifOrar; // tarif orar
private int oreLucrate; // ore lucrate
private double avansSalariu; // avans salariu

// constructor
public Angajati(String angNume, double tarifOrar, int oreLucrate, double avansSalariu) {
this.angNume = angNume;
this.tarifOrar = tarifOrar;
this.oreLucrate = oreLucrate;
this.avansSalariu = avansSalariu;
}

// getter nume
public String getNume() { return angNume; }

// setter nume
public void setNume(String angNume) { this.angNume = angNume; }

// getter tarif
public double getTarif() { return tarifOrar; }

// setter tarif
public void setTarif(double tarifOrar) { this.tarifOrar = tarifOrar; }

// getter ore
public int getOre() { return oreLucrate; }

// setter ore
public void setOre(int oreLucrate) { this.oreLucrate = oreLucrate; }

// getter avans
public double getAvans() { return avansSalariu; }

// setter avans
public void setAvans(double avansSalariu) { this.avansSalariu = avansSalariu; }

// toString
@override
public String toString() {
return "angajat: " + angNume + "\n" +
"tarif orar: " + tarifOrar + " RON\n" +
"ore lucrate: " + oreLucrate + "\n" +
"avans salariu: " + avansSalariu + " RON";
}
}
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import java.awt.*;

public class TihanIoan extends Frame {
// lista angajati
private List listAngajati = new List();

// casete de introducere text
private TextField txtNume = new TextField(15);
private TextField txtTarif = new TextField(10);
private TextField txtOre = new TextField(10);
private TextField txtAvans = new TextField(10);

// butoane
private Button btnAdauga = new Button("Adauga");
private Button btnSterge = new Button("Sterge");
private Button btnSetNume = new Button("Set Nume");
private Button btnSetTarif = new Button("Set Tarif");
private Button btnSetOre = new Button("Set Ore");
private Button btnSetAvans = new Button("Set Avans");

// etichete
private Label lblNume = new Label("Nume:");
private Label lblTarif = new Label("Tarif Orar:");
private Label lblOre = new Label("Ore Lucrate:");
private Label lblAvans = new Label("Avans Salariu:");
private Label lblLista = new Label("Lista Angajati:");

public TihanIoan() {
// setari fereastra
setTitle("Formular Angajati");
setSize(400, 300);
setLayout(new FlowLayout());

   // adaugare componente
   add(lblLista);
   add(listAngajati);


   add(lblNume); add(txtNume);
   add(lblTarif); add(txtTarif);
   add(lblOre); add(txtOre);
   add(lblAvans); add(txtAvans);


   add(btnAdauga);
   add(btnSterge);
   add(btnSetNume);
   add(btnSetTarif);
   add(btnSetOre);
   add(btnSetAvans);


   // inchidere fereastra
   addWindowListener(new java.awt.event.WindowAdapter() {
       public void windowClosing(java.awt.event.WindowEvent e) {
           dispose();
       }
   });


   setVisible(true);

}

public static void main(String[] args) {
new TihanIoan();
}
}
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import java.awt.;
import java.awt.event.;
import java.util.ArrayList;

// clasa principala
public class TihanIoan extends Frame {
private List angajatiList; // lista angajati
private TextField numeField, tarifField, oreField, avansField; // casete text
private TextArea infoArea; // zona informatii
private ArrayList angajati; // lista obiecte angajati

// constructor
public TihanIoan() {
angajati = new ArrayList<>(); // initializare lista
setLayout(new FlowLayout()); // layout simplu
setSize(800, 300); // dimensiune fereastra

   // lista angajati
   angajatiList = new List();
   angajatiList.addItemListener(e -> afiseazaDetalii()); // eveniment selectare
   add(angajatiList);


   // casete text
   numeField = new TextField(10);
   add(new Label("Nume:")); add(numeField);


   tarifField = new TextField(5);
   add(new Label("Tarif Orar:")); add(tarifField);


   oreField = new TextField(5);
   add(new Label("Ore Lucrate:")); add(oreField);


   avansField = new TextField(5);
   add(new Label("Avans Salariu:")); add(avansField);


   // butoane
   Button setNume = new Button("Set Nume");
   setNume.addActionListener(e -> setNume());
   add(setNume);


   Button setTarif = new Button("Set Tarif");
   setTarif.addActionListener(e -> setTarif());
   add(setTarif);


   Button setOre = new Button("Set Ore");
   setOre.addActionListener(e -> setOre());
   add(setOre);


   Button setAvans = new Button("Set Avans");
   setAvans.addActionListener(e -> setAvans());
   add(setAvans);


   Button adaugaAngajat = new Button("Adauga Angajat");
   adaugaAngajat.addActionListener(e -> adaugaAngajat());
   add(adaugaAngajat);


   Button afiseazaInfo = new Button("Afiseaza Info");
   afiseazaInfo.addActionListener(e -> afiseazaInfo());
   add(afiseazaInfo);


   // zona informatii
   infoArea = new TextArea(4, 50);
   infoArea.setEditable(false);
   add(infoArea);


   // inchidere fereastra
   addWindowListener(new WindowAdapter() {
       public void windowClosing(WindowEvent e) {
           dispose();
       }
   });

}

// setare nume
private void setNume() {
if (!angajati.isEmpty())
angajati.get(angajatiList.getSelectedIndex()).setNume(numeField.getText());
}

// setare tarif
private void setTarif() {
if (!angajati.isEmpty())
angajati.get(angajatiList.getSelectedIndex()).setTarif(Double.parseDouble(tarifField.getText()));
}

// setare ore
private void setOre() {
if (!angajati.isEmpty())
angajati.get(angajatiList.getSelectedIndex()).setOre(Integer.parseInt(oreField.getText()));
}

// setare avans
private void setAvans() {
if (!angajati.isEmpty())
angajati.get(angajatiList.getSelectedIndex()).setAvans(Double.parseDouble(avansField.getText()));
}

// adaugare angajat
private void adaugaAngajat() {
String nume = numeField.getText().isEmpty() ? "Anonim" : numeField.getText();
double tarif = tarifField.getText().isEmpty() ? 0.0 : Double.parseDouble(tarifField.getText());
int ore = oreField.getText().isEmpty() ? 0 : Integer.parseInt(oreField.getText());
double avans = avansField.getText().isEmpty() ? 0.0 : Double.parseDouble(avansField.getText());

   Angajati angajat = new Angajati(nume, tarif, ore, avans);
   angajati.add(angajat);
   angajatiList.add(nume);

}

// afisare detalii
private void afiseazaDetalii() {
if (!angajati.isEmpty() && angajatiList.getSelectedIndex() >= 0) {
Angajati angajat = angajati.get(angajatiList.getSelectedIndex());
numeField.setText(angajat.getNume());
tarifField.setText(String.valueOf(angajat.getTarif()));
oreField.setText(String.valueOf(angajat.getOre()));
avansField.setText(String.valueOf(angajat.getAvans()));
}
}

// afisare informatii
private void afiseazaInfo() {
if (!angajati.isEmpty() && angajatiList.getSelectedIndex() >= 0) {
infoArea.setText(angajati.get(angajatiList.getSelectedIndex()).toString());
}
}

// metoda principala
public static void main(String[] args) {
new TihanIoan().setVisible(true);
}
}

Java methods and classes examples

Vaniusca 23 — Sat, 25 Jan 2025 17:57:52 +0000

What is a Class in Java? A class is a blueprint for creating objects. It defines attributes (variables) and methods (functions) that describe the behavior of an object.

Basic Syntax of a Class

`// defining a class
public class Car {
// attributes (variables)
String brand;
int speed;

// method (function)
void honk() {
    System.out.println("Beep Beep!");
}

}`
📌 Explanation:

Car is a class.
brand and speed are attributes (also called instance variables).
honk() is a method (a function inside a class).

How to Create an Object? An object is an instance of a class. You create objects using the new keyword.

Creating an Object in Java

`public class Main {
public static void main(String[] args) {
// creating an object of the Car class
Car myCar = new Car();

    // assigning values to attributes
    myCar.brand = "Toyota";
    myCar.speed = 120;

    // calling a method
    myCar.honk();

    // printing attributes
    System.out.println("Brand: " + myCar.brand);
    System.out.println("Speed: " + myCar.speed + " km/h");
}

}`
🔹 Output:

makefile
Beep Beep!
Brand: Toyota
Speed: 120 km/h
📌 Explanation:

Car myCar = new Car(); → Creates an object named myCar.
myCar.brand = "Toyota"; → Assigns a value to brand.
myCar.honk(); → Calls the honk() method.

Constructors in Java A constructor is a special method that is automatically called when an object is created.

Example of a Constructor

`public class Car {
String brand;
int speed;

// constructor
public Car(String brand, int speed) {
    this.brand = brand;
    this.speed = speed;
}

// method to display car details
void displayCar() {
    System.out.println("Brand: " + brand);
    System.out.println("Speed: " + speed + " km/h");
}

}

public class Main {
public static void main(String[] args) {
// using constructor to initialize values
Car myCar = new Car("Honda", 150);
myCar.displayCar();
}
}`
🔹 Output:

Brand: Honda
Speed: 150 km/h
📌 Explanation:

The constructor Car(String brand, int speed) initializes attributes when the object is created.
The this keyword refers to the current object's instance.

Types of Methods in Java Java has two types of methods:

Instance Methods (work with object data)
Static Methods (belong to the class, not objects)
Example of Instance and Static Methods

`public class MathOperations {
// instance method
int square(int x) {
return x * x;
}

// static method
static int add(int a, int b) {
    return a + b;
}

}

    // calling a static method
    int sum = MathOperations.add(10, 20);
    System.out.println("Sum: " + sum);
}

}`
🔹 Output:

Square: 25
Sum: 30
📌 Explanation:

Method Overloading in Java Method Overloading allows multiple methods with the same name but different parameters.

Example of Method Overloading

`public class Calculator {
// method with two parameters
int add(int a, int b) {
return a + b;
}

// overloaded method with three parameters
int add(int a, int b, int c) {
    return a + b + c;
}

}

Sum (2 numbers): 30
Sum (3 numbers): 60
📌 Explanation:

The method add() is overloaded (two versions with different numbers of parameters).
The compiler automatically selects the correct method.

// clasa student
public class Student {
private String stdNume, denDisc1, denDisc2, denDisc3; // nume student si discipline
private int note1, note2, note3; // note pentru discipline

// constructor
public Student(String stdNume, String denDisc1, String denDisc2, String denDisc3) {
this.stdNume = stdNume;
this.denDisc1 = denDisc1;
this.denDisc2 = denDisc2;
this.denDisc3 = denDisc3;
this.note1 = 0;
this.note2 = 0;
this.note3 = 0;
}

// get/set nume
public String getNume() { return stdNume; }
public void setNume(String stdNume) { this.stdNume = stdNume; }

// get/set disciplina 1
public String getDisc1() { return denDisc1; }
public void setDisc1(String denDisc1) { this.denDisc1 = denDisc1; }

// get/set disciplina 2
public String getDisc2() { return denDisc2; }
public void setDisc2(String denDisc2) { this.denDisc2 = denDisc2; }

// get/set disciplina 3
public String getDisc3() { return denDisc3; }
public void setDisc3(String denDisc3) { this.denDisc3 = denDisc3; }

// get/set nota 1
public int getNota1() { return note1; }
public void setNota1(int note1) { this.note1 = note1; }

// get/set nota 2
public int getNota2() { return note2; }
public void setNota2(int note2) { this.note2 = note2; }

// get/set nota 3
public int getNota3() { return note3; }
public void setNota3(int note3) { this.note3 = note3; }

// toString
@override
public String toString() {
return "student: " + stdNume + "\n" +
"disciplina 1: " + denDisc1 + " nota: " + note1 + "\n" +
"disciplina 2: " + denDisc2 + " nota: " + note2 + "\n" +
"disciplina 3: " + denDisc3 + " nota: " + note3;
}
}
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
import java.awt.*;

// clasa principala
public class TihanIoan extends Frame {
private Choice cmbDiscipline; // combobox
private List listaNote; // lista note
private TextField txtNota; // caseta text
private Label lblInfo; // eticheta
private Button btnSetNota, btnAdauga, btnAfisare; // butoane
private Student student; // obiect student

public TihanIoan() {
// initializare student
student = new Student("Ioan Tihan", "Matematica", "Informatica", "Fizica");

   // setari fereastra
   setTitle("formular student");
   setSize(400, 300);
   setLayout(new FlowLayout());


   // combobox discipline
   cmbDiscipline = new Choice();
   cmbDiscipline.add(student.getDisc1());
   cmbDiscipline.add(student.getDisc2());
   cmbDiscipline.add(student.getDisc3());
   add(cmbDiscipline);


   // caseta text pentru nota
   txtNota = new TextField(10);
   add(new Label("Introdu nota:"));
   add(txtNota);


   // lista note
   listaNote = new List();
   add(listaNote);


   // butoane
   btnSetNota = new Button("Set Nota");
   btnAdauga = new Button("Adauga Nota");
   btnAfisare = new Button("Afiseaza Info");


   add(btnSetNota);
   add(btnAdauga);
   add(btnAfisare);


   // eticheta informatii
   lblInfo = new Label("detalii student");
   add(lblInfo);


   // inchidere fereastra
   addWindowListener(new java.awt.event.WindowAdapter() {
       public void windowClosing(java.awt.event.WindowEvent e) {
           dispose();
       }
   });


   setVisible(true);

}

public static void main(String[] args) {
new TihanIoan();
}
}
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
import java.awt.;
import java.awt.event.;
import java.util.ArrayList;

public class TihanIoan extends Frame {
private Choice discipline;
private List noteList;
private TextField notaField;
private TextArea infoArea;
private Student student;
private ArrayList noteDisc1, noteDisc2, noteDisc3;

public TihanIoan() {
student = new Student("Ioan Tihan", "Matematica", "Informatica", "Fizica");
noteDisc1 = new ArrayList<>();
noteDisc2 = new ArrayList<>();
noteDisc3 = new ArrayList<>();

   setLayout(new FlowLayout());
   setSize(500, 350);




   discipline = new Choice();
   discipline.add(student.getDisc1());
   discipline.add(student.getDisc2());
   discipline.add(student.getDisc3());
   add(discipline);




   noteList = new List();
   add(noteList);




   notaField = new TextField(5);
   add(notaField);




   Button afisareNote = new Button("Afisare Note");
   afisareNote.addActionListener(e -> afiseazaNote());
   add(afisareNote);




   Button adaugaNota = new Button("Adauga Nota");
   adaugaNota.addActionListener(e -> adaugaNota());
   add(adaugaNota);




   Button afisareInfo = new Button("Afisare Info");
   afisareInfo.addActionListener(e -> afiseazaInfo());
   add(afisareInfo);




   infoArea = new TextArea(7, 50);
   infoArea.setEditable(false);
   add(infoArea);




   addWindowListener(new WindowAdapter() {
       public void windowClosing(WindowEvent e) {
           dispose();
       }
   });

}

private void afiseazaNote() {
noteList.removeAll();
ArrayList note = getNoteList();
for (int nota : note) {
noteList.add(String.valueOf(nota));
}
}

private void adaugaNota() {
try {
int nota = Integer.parseInt(notaField.getText());
if (nota < 1 || nota > 10) {
infoArea.setText("Introduceți o notă între 1 și 10.");
return;
}

       ArrayList<Integer> note = getNoteList();
       if (!note.isEmpty() && note.get(note.size() - 1) >= 5) {
           infoArea.setText("Studentul a promovat disciplina și nu mai poate adăuga note.");
           return;
       }




       note.add(nota);
       afiseazaNote();
       afiseazaInfo();
   } catch (NumberFormatException e) {
       infoArea.setText("Introduceți o notă validă.");
   }

}

private void afiseazaInfo() {
StringBuilder info = new StringBuilder("Student: " + student.getNume() + "\nNote:\n");
info.append(student.getDisc1()).append(" ").append(noteDisc1).append("\n");
info.append(student.getDisc2()).append(" ").append(noteDisc2).append("\n");
info.append(student.getDisc3()).append(" ").append(noteDisc3);
infoArea.setText(info.toString());
}

private ArrayList getNoteList() {
String disciplina = discipline.getSelectedItem();
if (disciplina.equals(student.getDisc1())) return noteDisc1;
if (disciplina.equals(student.getDisc2())) return noteDisc2;
return noteDisc3;
}

public static void main(String[] args) {
new TihanIoan().setVisible(true);
}
}

How to make use of outer joins and rollup in oracle sql

Vaniusca 23 — Fri, 24 Jan 2025 17:52:55 +0000

--1.Sa se afiseze first_name managerului, department_name si city pentru toate departamentele din baza de date. In cazul in care un departament nu are manager, se va afisa "Fara manager" in campul first_name

select coalesce (e.first_name, 'Fara manager') as manager_name, d.department_name, l.city
from hr.departments d
left join  hr.employees e on d.manager_id = e.employee_id
join hr.locations  on d.location_id = l.location_id;

--2.Folosind “joncțiunea externă” sa se afișeze numele departamentelor care nu au angajați.

select department_name from hr.departments d full outer join hr.employees e on d.department_id = e.department_id where e.employee_id is null;

–2’.(extra)8.Folosind "jonctiunea externa" (1pct) sa se afiseze numele departamentelor care nu au angajati in "JOB_HISTORY". (5)
select d.department_name from hr.departments d left outer join hr.job_history jh on d.department_id = jh.department_id where jh.department_id is null -- Nu a avut niciun angajat care să fi părăsit departamentul and d.department_id in (select distinct department_id from hr.employees);

--3.Folosind ROLLUP(1pct), reuniuni(2pct) sa se afiseze departamentele, managerii și numarul de angajati afisandu-se subtotaluri la nivel de manageri, departamente și total general.

`–rollup
select
decode (grouping(d.department_id),
1, 'total department',
nvl(to_char(d.department_id), ‘fara departament’)) as department_id,
decode(grouping(e.manager_id),
1, 'subtotal manager',
to_char(e.manager_id)) as manager_id,
count (*) as nr_angajati
from hr.employees e
left join hr.departments d on e.department_id = d.department_id
group by rollup (d.department_id, e.manager_id)
order by department_id nulls last, manager_id nulls last;

–reuniuni
select nvl(to_char(d.department_id), 'fara departament') as department_id,
to_char(e.manager_id) as manager_id,
count (*) as nr_angajati
from hr.employees e
left join hr.departments d on e.department_id = d.department_id
group by d.department_id, e.manager_id

union all

select nvl (to_char(d.department_id), 'fara departament') as department_id,
null as manager_id,
count (*) as nr_angajati
from hr.employees e
left join hr.departments d on e.department_id = d.department_id
group by d.department_id

union all

select'total departament' as department_id,
null as manager_id,
count (*) as nr_angajati
from hr.employees
order by department_id nulls last, manager_id nulls last;

–combinat
select
decode(grouping_id(d.department_id, e.manager_id), 0, nvl(to_char(d.department_id), 'fara departament'),
1, 'subtotal manager',

2, 'total departament',
3, 'total general' )
as department_id, decode(grouping_id(d.department_id, e.manager_id), 0,
to_char (e.manager_id), 1, null, 2, null, 3, null ) as manager_id, count (*) as nr_angajati
from hr.employees e
left join hr.departments d on e.department_id = d.department_id
group by grouping sets ((d.department_id, e.manager_id), (d.department_id), ())
order by department_id nulls last, manager_id nulls last;`

--4.Folosind “start with” sa se afiseze subordonatii subordonatilor angajatului 109.

select employee_id, first_name, last_name from hr.employees where level = 2 start with manager_id = 109 connect by prior employee_id = manager_id;
--5.Sa se creeze o procedura denumita SUMA, care sa afiseze suma salariilor tuturor angajatilor.

create or replace PROCEDURE SUMA AS v_total_salary NUMBER; BEGIN SELECT SUM(salary) INTO v_total_salary FROM hr.employees; DBMS_OUTPUT.PUT_LINE('Suma salariilor tuturor angajatilor este: ' || v_total_salary); END SUMA;

--6.Sa se creeze o procedura care sa afiseze cati angajati sunt intr-un departament. Departamentul va fi introdus la executie ca și parametru al procedurii.

`create or replace PROCEDURE numar_angajati_departament (
p_department_name IN hr.departments.department_name%TYPE
) IS
v_numar_angajati NUMBER;
BEGIN
-- Selectăm numărul de angajați din departamentul specificat
SELECT COUNT(employee_id)
INTO v_numar_angajati
FROM hr.employees e
JOIN hr.departments d ON e.department_id = d.department_id
WHERE d.department_name = p_department_name;

-- Afișăm rezultatul
DBMS_OUTPUT.PUT_LINE('Numarul de angajati in departamentul ' || p_department_name || ' este: ' || v_numar_angajati);

END;`

--7.Sa se creeze o functie ca un parametru care sa returneze cate orase din bază de date sunt din US. Acest numar va fi afisat după linia cu apelul functiei.

`--functia propriu zisa
create or replace FUNCTION numar_orase_sua
RETURN NUMBER IS
v_numar_orase NUMBER;
BEGIN
-- Selectăm numărul de orașe unde country_id este 'US'
SELECT COUNT(DISTINCT city)
INTO v_numar_orase
FROM hr.locations
WHERE country_id = 'US';

-- Returnăm valoarea
RETURN v_numar_orase;

END;

--rezultat
SET SERVEROUTPUT ON;
DECLARE
v_total_orase NUMBER;
BEGIN
-- Apelăm funcția și stocăm rezultatul
v_total_orase := numar_orase_sua;

-- Afișăm rezultatul
DBMS_OUTPUT.PUT_LINE('Numarul de orase din SUA este: ' || v_total_orase);

END;`