在Java中使用参数化构造函数创建对象时出错

Question

I'm getting below error when creating object along with parameterized constructor.

Main.java:6: error: constructor Cipher in class Cipher cannot be applied to given types

Cipher cy = new Cipher(k);              ^

required: no arguments

found: int

reason: actual and formal argument lists differ in length

Here is my files looks like

<b>Main.java</b>

public class Main {
    public static void main(String []args){
   int k=8;
      Cipher cy = new Cipher(k);
      String encrypted_msg = cy.encrypt(message);
      String decrypted_msg = cy.decrypt(encrypted_msg);
      view1.displayResult("Decrypted message: "+decrypted_msg);
        }
    }

<b>Cipher.java</b>

import java.util.*;
public class Cipher
    {
    private int key;
    // Constructor 
    public void Cipher(int k)
        {
        key = k; 
        }// end Constructor 

    } // end class 

Answer 1

Change

public void Cipher(int k)

to

public Cipher(int k)

With a return type of void , that is not a constructor. In Java, a constructor does not specify a return type. The return type is simply the name of the class.

So in your example, because you have not defined a constructor, Java will provide a default no-argument constructor of the following format:

public Cipher() {}

thus the error message is telling you that only a no-argument constructor exists, but you are calling a constructor that expects an int argument.

Answer 2

<b>Cipher.java</b>

import java.util.*;
public class Cipher
    {
    private int key;
    public Cipher(int k) //remove the void
        {
        this.key = k; //use this for object level reference
        } 

    }