拷贝构造函数示例_带有示例的Java构造函数

灰太狼 2023-03-05 12:38 1阅读 0赞

拷贝构造函数 示例

## Java构造函数 **(**Java Constructor**)** ##

*  A **constructor** is a special function or method to initialize an object when it is created.
    
    **构造函数**是一种特殊的函数或方法，用于在创建对象时对其进行初始化。
 *  **Constructor** name must be the same as the class name.
    
    **构造函数**名称必须与类名称相同。
 *  The syntax of the **constructor** is similar as method except constructors have no explicit return type.
    
    **构造函数**的语法与方法相似，只是构造函数没有显式的返回类型。

### 构造目的 **(**Purpose of Constructor**)** ###

The purpose of a constructor is to assign initial values to the instance variables at runtime.

构造函数的目的是在运行时将初始值分配给实例变量。

### 构造函数的类型 **(**Types of Constructors**)** ###

There are two types of constructor in java and the name of those constructors given below:

Java中有两种类型的构造函数，下面给出了这些构造函数的名称：

1.  Default Constructor or No argument Constructor
    
    默认构造函数或无参数构造函数
2.  Parameterized Constructor
    
    参数化构造函数

### 1)默认构造函数或无参数构造函数 **(**1) Default Constructor or No argument Constructor**)** ###

Here we will discuss in detail...

在这里，我们将详细讨论...

*  Default Constructor or No argument constructor is that constructor which takes no argument.
    
    默认构造函数或无参数构造函数是不带参数的构造函数。
 *  In this constructor, we don’t pass any argument or parameter.
    
    在此构造函数中，我们不传递任何参数或参数。
 *  When we don’t include any constructor in the class so java compiler calls this constructor by default that is the name of this constructor is default constructor.
    
    当我们在类中不包含任何构造函数时，java编译器会默认调用该构造函数，即该构造函数的名称为默认构造函数。

**Syntax:**

**句法：**

class Classname{
            Classname(){
                // initialization of instance variable
            }
        }

**Example:**

**例：**

import java.util.*;
    
    // Class Declaration
    class Constr {
        
        // Declaring str instance variable of String type
        String str;
        // Constructor Definition
        Constr() {
        
            str = "Hello World!!";
        }
    }
    
    public class Main {
        
        public static void main(String[] args) {
        
            // Constructor Calling
            Constr con = new Constr();
            System.out.println(con.str);
        }
    
    }

**Output**

**输出量**

D:\Programs>javac Main.java
    D:\Programs>java Main
    Hello World !!

### 2)参数化构造函数 **(**2) Parameterized Constructor**)** ###

Here we will discuss in detail...

在这里，我们将详细讨论...

*  Parameterized Constructor are those constructor which takes argument explicitly.
    
    参数化构造函数是显式接受参数的那些构造函数。
 *  In this constructor we must pass argument or parameter.
    
    在此构造函数中，我们必须传递参数或参数。
 *  When we include both constructor (Default and Parameterized) in the class so java compiler does not call this constructor bydefault (i.e. this constructor will be called explicitly).
    
    当我们在类中同时包含构造函数(Default和Parameterized)时，java编译器不会默认调用该构造函数(即，将显式调用此构造函数)。

**Syntax:**

**句法：**

class Classname{
            Classname(datatype arg1, datatype arg2, ...){
                // initialization of instance variable
            }
        }

**Example:**

**例：**

import java.util.*;
    
    // Class Declaration
    class ParamConstr {
        
        // Instance Variable
        String str;
        // Constructor Definition
        ParamConstr(String stri) {
        
            str = stri;
        }
    }
    
    public class Main {
        
        public static void main(String[] args) {
        
            // Calling Parameterized Constructor
            ParamConstr pcon = new ParamConstr("Hi, Welcome in parametrized constructor");
            System.out.println(pcon.str);
        }
    }

**Output**

**输出量**

D:\Programs>javac Main.java
    
    D:\Programs>java Main
    Hi, Welcome in parameterized constructor

> 翻译自: [https://www.includehelp.com/java/java-constructors-with-examples.aspx][https_www.includehelp.com_java_java-constructors-with-examples.aspx]

拷贝构造函数 示例

[https_www.includehelp.com_java_java-constructors-with-examples.aspx]: https://www.includehelp.com/java/java-constructors-with-examples.aspx