Java中的超级构造函数 [英] Super constructor in java

问题描述

请解释

public class Contact {
    private String contactId;
   private String firstName;
    private String lastName;
    private String email;
    private String phoneNumber;

public Contact(String contactId,String firstName, String lastName,   String email,        String phoneNumber) {
    super();  //what does standalone super() define? With no args here?
    this.firstName = firstName;  
    this.lastName = lastName;     //when is this used?, when more than one args to be entered?
    this.email = email;
    this.phoneNumber = phoneNumber;
}

Super（）里面没有参数，意味着有多个参数定义的？并借助 this.xxx完成此操作吗？

Super() with no arguments inside mean there are more than one arguments to be defined? And is this done with the help of "this.xxx" ?

为什么我们在公共类联系人本身中定义了dint。为什么我们要再次定义并在此处调用其参数？

Why dint we define in the "public class Contact" itself. Why we defined again and called its arguments here?

推荐答案

Super（）不带

否， super（ ）只是调用基类的no-arg构造函数，在您的情况下是 Object 。

No, super() just calls the no-arg constructor of the base class, in your case Object.

它什么也没做。它只是在代码中明确指出，您正在使用no-arg构造函数构造基类。实际上，如果省略 super（），编译器将隐式地将其添加回去。

It does nothing really. It just makes it explicit in the code, that you're constructing the base class using the no-arg constructor. In fact, if you left super() out, it would be added back implicitly by the compiler.

因此 super（）的含义是什么？好吧，在某些情况下，类没有no-arg构造函数。此类的子类必须使用诸如 super（ hello）显式调用某些超级构造函数。

So what is the super() for if it's added implicitly anyway? Well, in some cases, a class does not have a no-arg constructor. Subclasses of this class must explicitly call some super-constructor, using for instance super("hello").

this.lastName = lastName; //何时使用此参数？何时输入多个参数？

this.lastName = lastName; //when is this used?, when more than one args to be entered?

this.lastName = lastName; 与 super（）无关。它仅说明构造函数自变量 lastName 的值应分配给成员变量 lastName 。等效于

this.lastName = lastName; has nothing to do with super(). It merely states that the value of the constructor argument lastName should be assigned to the member variable lastName. This is equivalent to

public Contact(String contactId, String firstName, String lastNameArg,
               String email, String phoneNumber) {
    // ...
    lastName = lastNameArg;
    // ...

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