Concrete Class in Java

In-depth understanding of specific classes in Java

In Java, the concrete class refers to a complete class implementation that contains the specific implementation of all methods, without unimplemented methods. Concrete classes can extend abstract classes or implement interfaces. We can use the new keyword to create objects of concrete classes. It is also called a 100% implemented class in Java.

Pros and cons of specific classes in Java

The specific classes in Java have many advantages and disadvantages:

Pros

• Decompose complex designs: Helps break down complex designs into smaller, easy-to-manage modules.
• Reduce object dependencies: Reduce dependencies between objects and improve code maintainability and reusability.
• Supports multiple implementations: Can easily implement a variety of different functions.
• Scalability: Can extend interfaces and abstract classes.

Disadvantages

• Poor flexibility: Compared with abstract classes and interfaces, the flexibility is lower.
• Labor polymorphism: Specific classes themselves do not directly support polymorphism, and need to be implemented through inheritance and interfaces.

Step for defining Java specific classes

The following steps describe how to declare and use specific classes in a Java environment:

1. Start: Start Java program.
2. Import package: Import the necessary Java packages.
3. Declare class: Declare a public class.
4. Declare variables: Declare the required variables.
5. Return value: Define the return value of the method.
6. Abstract method: (If inherited from an abstract class) Implement abstract method.
7. Inheritance: (If required) Inherit the parent class.
8. Main method: Declare main Method.
9. Parameters: Declare the parameters of the main method.
10. Print Output: Print the required value.
11. Get the return value: Get the return value of the method.
12. End:End Java program.

Syntax example of Java concrete class

The following code shows how to declare and use specific classes:

class ConcreteCalculator {
    static int add(int a, int b) {
        return a + b;
    }
    static int subtract(int a, int b) {
        return a - b;
    }
    static int multiply(int a, int b) {
        return a * b;
    }
    static int divide(int a, int b) {
        return a / b;
    }
    public static void main(String[] args) {
        int sum = add(10, 5); // 使用具体类方法
        int diff = subtract(10, 5);
        int prod = multiply(10, 5);
        int div = divide(10, 5);
        System.out.println("Sum: " + sum);
        System.out.println("Difference: " + diff);
        System.out.println("Product: " + prod);
        System.out.println("Division: " + div);
    }
}

abstract class Shape {
    abstract double area();
    abstract double perimeter();
}

class Circle extends Shape {
    double r = 5;
    public double area() {
        return 3.14 * r * r;
    }
    public double perimeter() {
        return 2 * 3.14 * r;
    }
}

// ... (Triangle and Square classes similar to Circle) ...

This code shows the ConcreteCalculator concrete classes and Shape abstract classes and their specific subclasses (Circle, Triangle, Square).

How to use

The following two methods of using specific classes are provided:

Method 1: Use the specific class of sum and product methods

public class ARBRDD {
    static int product(int a, int b) {
        return a * b;
    }
    static int sum(int a, int b) {
        return a + b;
    }
    public static void main(String args[]) {
        int p = product(16, 7);
        int s = sum(7, 16);
        System.out.println("Product: " + p);
        System.out.println("Sum: " + s);
    }
}

Method 2: Define an abstract class containing specific methods and use the ShapeUtil class

class ConcreteCalculator {
    static int add(int a, int b) {
        return a + b;
    }
    static int subtract(int a, int b) {
        return a - b;
    }
    static int multiply(int a, int b) {
        return a * b;
    }
    static int divide(int a, int b) {
        return a / b;
    }
    public static void main(String[] args) {
        int sum = add(10, 5); // 使用具体类方法
        int diff = subtract(10, 5);
        int prod = multiply(10, 5);
        int div = divide(10, 5);
        System.out.println("Sum: " + sum);
        System.out.println("Difference: " + diff);
        System.out.println("Product: " + prod);
        System.out.println("Division: " + div);
    }
}

abstract class Shape {
    abstract double area();
    abstract double perimeter();
}

class Circle extends Shape {
    double r = 5;
    public double area() {
        return 3.14 * r * r;
    }
    public double perimeter() {
        return 2 * 3.14 * r;
    }
}

// ... (Triangle and Square classes similar to Circle) ...

Summary

Specific classes are basic and important components in Java programming. This article explains in detail the concepts, advantages and disadvantages, definition steps and usage methods of specific classes, and explains them through code examples. Understanding specific classes is essential to writing efficient and maintainable Java programs.

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