构造函数和方法之间的差异 [英] Difference between constructors and methods

问题描述

Bellow是我在Tutorials Points上发现的一个例子，它是一个构造函数的例子。我得到了大多数，但我只是不知道为什么你需要一个构造函数和一个方法。

Bellow is an example I found on Tutorials Points, an example of a constructor. I got most of them, but I just don't get why you need a constructor and a method.

public Puppy(String name){
    System.out.println("Passed Name is :" + name ); 
}

我的问题是，什么阻止你这样做？

My question is, what stops you from doing this instead?

public static void Puppy(String name){
    System.out.println("Passed Name is: "+name);
}

这两个不一样吗？

这是完整的程序参考：

public class Puppy {
    int puppyAge;

    public Puppy(String name) {
        System.out.println("Passed Name is :" + name); 
    }

    public void setAge(int age) {
        puppyAge = age;
    }

    public int getAge() {
        System.out.println("Puppy's age is :" + puppyAge); 
        //what does this return do? since the puppyAge is already printed above.
        return puppyAge;
    }

    public static void main(String []args){
        Puppy myPuppy = new Puppy("tommy");

        myPuppy.setAge(2);
        myPuppy.getAge();

        System.out.println("Variable Value :" + myPuppy.puppyAge); 
    }
}

推荐答案

没有得到一个实例的基本概念，这是OOP的根本。如果你想要一个比喻，让我们谈谈汽车。

You did not get the basic concept of an instance, which is fundamental in OOP. If you want a metaphor, let's talk about cars.

我很确定你知道一辆汽车是什么;你知道它使你能够从一个地方移动到另一个地方，它有4个轮子等。这是一个概念，您在车库中的实际汽车是此概念的实例（< = class ）。

I'm pretty sure you know what a car is; you know that it enables you to move from one place to another, that it has 4 wheels and so on. It is a concept, and the actual car you have in your garage is an instance of this concept (<=> class).

构造函数的目标是创建一个实例，而不是打印一些文本。没有构造函数，你永远不能调用你的类的非静态方法。你不能驾驶汽车的概念，你将需要先建造一辆汽车。

A constructor's goal is to create an instance, not to print some text. Without a constructor, you will never be able to call a non-static method of your class. You won't be able to drive the concept of a car, you will need to build a car first.

只需查看那些概念;你将无处没有它。

Just review those notions; you will get nowhere without it.

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