Java Generics - School4Tech

Generics in Java is a mechanism for declaring types that can be used with objects of various types. Generics allow a single implementation to be used with multiple data types, which increases the flexibility and reusability of code.

There are two types of generics in Java:

Class-level generics: These are generics that are applied to a class. For example, a generic class might be declared as class MyClass<T> { ... }, where T represents the type of object that will be used with the class.

Here’s an example of how you could use generics with a Car class:

class Car<T> {
  private T model;

  public Car(T model) {
    this.model = model;
  }

  public T getModel() {
    return model;
  }
}

class Sedan extends Car<String> {
  public Sedan(String model) {
    super(model);
  }
}

class Hatchback extends Car<Integer> {
  public Hatchback(Integer model) {
    super(model);
  }
}

public static void main(String[] args) {
  Car<String> sedan = new Sedan("Sedan");
  Car<Integer> hatchback = new Hatchback(1);

  System.out.println(sedan.getModel());
  System.out.println(hatchback.getModel());
}

class Car<T> {

private T model;

public Car(T model) {

this.model = model;

}

public T getModel() {

return model;

}

class Sedan extends Car<String> {

public Sedan(String model) {

super(model);

}

class Hatchback extends Car<Integer> {

public Hatchback(Integer model) {

super(model);

}

public static void main(String[] args) {

Car<String> sedan = new Sedan("Sedan");

Car<Integer> hatchback = new Hatchback(1);

System.out.println(sedan.getModel());

System.out.println(hatchback.getModel());

}

In this example, we have created a generic Car class that can be used with either String or Integer types, depending on the implementation. The Sedan and Hatchback classes extend the Car class and specify the type they will use (String and Integer, respectively). When creating instances of these classes, we can then access the model through the getModel method and see that it returns the correct value for each type.Regenerate response

Method-level generics: These are generics that are applied to a method. For example, a generic method might be declared as public static <T> T myMethod(T t) { ... }, where T represents the type of object that will be passed to the method as an argument.

example:

Here’s an example of how you could use method-level generics with a Car class:

class Car {
  private Object model;

  public Car(Object model) {
    this.model = model;
  }

  public <T> T getModel(Class<T> clazz) {
    return clazz.cast(model);
  }
}

public static void main(String[] args) {
  Car sedan = new Car("Sedan");
  Car hatchback = new Car(1);

  System.out.println(sedan.getModel(String.class));
  System.out.println(hatchback.getModel(Integer.class));
}

class Car {

private Object model;

public Car(Object model) {

this.model = model;

}

public <T> T getModel(Class<T> clazz) {

return clazz.cast(model);

}

public static void main(String[] args) {

Car sedan = new Car("Sedan");

Car hatchback = new Car(1);

System.out.println(sedan.getModel(String.class));

System.out.println(hatchback.getModel(Integer.class));

}

In this example, we have created a Car class with a single model property. The getModel method is a generic method that takes a Class object as an argument and returns an object of that type. When we create instances of the Car class and call the getModel method, we pass in the appropriate class for the type of object we want to retrieve (String.class or Integer.class). The method then uses the clazz.cast method to cast the model object to the correct type and return it.Regenerate response

Leave a Comment Cancel Reply