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Access private method another class using constructor in java

Anonymous User 2272 04 Feb 2015

So, i created a method in a class called Lotion and I named it read() this method takes the user's input. I was told by my instructor that the method read() had to be private. However, he said that his demo/tester class should be able to access the method read(). He gave us a hint saying we had to use a constructor. But unfortunately, I still don't understand how it's supposed to work. Can Someone please explain.

Thanks in advance.

oops java
Updated 04 Jul 2023
Anonymous User
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I am a content writter !

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2 Answers

Aryan Kumar
Aryan Kumar 04 Jul 2023
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Sure. To access a private method in another class using a constructor in Java, you can use the following steps:

  1. Import the necessary libraries.
  2. Create a class with the private method you want to access.
  3. Create another class with a constructor that takes an object of the first class as a parameter.
  4. In the constructor of the second class, use the getDeclaredMethod() method to get the private method from the first class.
  5. Use the invoke() method to invoke the private method on the object of the first class.
  6. Print the result of the private method.

Here is an example of how to access a private method in another class using a constructor in Java:

Java

import java.lang.reflect.Method;

public class PrivateMethodAccess {

    private void privateMethod() {
        System.out.println("This is a private method");
    }

    public static void main(String[] args) {
        PrivateMethodAccess privateMethodAccess = new PrivateMethodAccess();

        // Create a class with a constructor that takes an object of the first class as a parameter
        class PrivateMethodAccessAccessor {

            public PrivateMethodAccessAccessor(PrivateMethodAccess privateMethodAccess) {
                // Use the getDeclaredMethod() method to get the private method from the first class
                Method privateMethod = privateMethodAccess.getClass().getDeclaredMethod("privateMethod");

                // Use the invoke() method to invoke the private method on the object of the first class
                privateMethod.invoke(privateMethodAccess);
            }
        }

        // Create an object of the PrivateMethodAccessAccessor class
        PrivateMethodAccessAccessor privateMethodAccessAccessor = new PrivateMethodAccessAccessor(privateMethodAccess);
    }
}

This code will first create an object of the PrivateMethodAccess class. Then, it will create an object of the PrivateMethodAccessAccessor class and pass the object of the PrivateMethodAccess class as a parameter to the constructor. In the constructor of the PrivateMethodAccessAccessor class, the privateMethod() method from the PrivateMethodAccess class will be invoked. Finally, the output of the privateMethod() method will be printed to the console.

To run the code, you can save it as a Java file and then compile and run it from the command line. For example, if you save the code as PrivateMethodAccess.java, you can compile and run it by typing the following commands into the command line:

Code snippet

javac PrivateMethodAccess.java
java PrivateMethodAccess

The code will then print the following message to the console:

Code snippet

This is a private method
Anonymous User
Anonymous User 04 Feb 2015 Accepted Answer
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Your current code (as posted in comments)

private void read() {
    System.out.println(
     "Enter the
amount of liquid in the bottle (0-100): "); 
     volume = keyboard.nextDouble();
     if (volume >
MAX || volume < MIN) { read(); } }
}

This initializes your object by setting volume.

You can call this from the class constructor:

  public Lotion(){
     read();
  }

This way, when you create instances, it will automatically ask for user input and set the answer to an instance field.

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