The Person class's adjustAge method should increase the Person's age by 20. Why is my code not good?

Question about the task

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After three days I need to ask for help! Where am I going wrong? The error being validated tells me The Person class's adjustAge method should increase the Person's age by 20. The printed output is 40 , I think I did not understand well .. I tried with:

Person person = new Person();
this.age = age;
age = person.age + 20;

and with

this.age = age;
age = age + 20;

inside the adjustAge method, isn't the method increase +20 with my code? Thank you in advance.

Think about what the program is doing.
Fix the programming error so that person.age changes value.

Hint: carefully review the adjustAge method.

Requirements:

The program should display text on the screen.
The Person class should have a public int field called age.
The Person class's adjustAge method should display text on the screen.
The Person class's adjustAge method must have only one int parameter named age, and the method must be void.
The main method should call the adjustAge method only once.
The Person class's adjustAge method should increase the Person's age by 20.

package en.codegym.task.jdk13.task04.task0401; /* This age doesn't work for me… */ public class Solution { public static void main(String[] args) { Person person = new Person(); //System.out.println("Age: " + person.age); person.adjustAge(person.age); //System.out.println("Adjusted age: " + person.age); } public static class Person { public int age = 20; public void adjustAge(int age) { Person person = new Person(); this.age = age; age = person.age + 20; System.out.println("The age in adjustAge() is: " + age); } } }

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Sneha Kurmi Machine Learning Engineer

11 May 2024, 15:05

Since this is years old post, I understand you would have moved on from this question. But I would like to present the info that really made me understand where I was going wrong and maybe clear future newcomers doubt. At first glance at the code I thought 'nothing seems wrong with the code, it matches all the conditions' and decided 'lets just run the code without any changes and see what goes amiss. without any changes to the code - every condition was met except the last one "The Person class's adjustAge method should increase the Person's age by 20." well, then what the heck '

age = age + 20

' is actually updating? the adjustAge method was not working because it was modifying the local variable age instead of the age field of the Person object. In Java, when you pass a variable to a method, it creates a copy of that variable, so modifications made inside the method do not affect the original variable. In the original code, the adjustAge method was modifying this copy, not the actual age field of the Person object. Using this keyword refers to the current object. It is used to differentiate between instance variables and parameters with the same name. After reading this info, it made sense as to why:

this.age = age + 20;
System.out.println(".... " + this.age);

Give 'Variable shadowing in Java' a read to clear this concept more!

Artem Divertitto Senior Android Developer at United Tech

22 March 2022, 21:37

You shouldn't create Person person = new Person(); inside adjustAge, use only current instance(this)

Anonymous #10960894

Level 19 , Arnold, United Kingdom

18 March 2022, 11:33

The point of the exercise is to teach the difference between an instance variable and a class variable. Person.age refers to the default age for any instance of the Person class. person.age or this.age refers to the age of the current instance. Reset the task then change Person.age = age to person.age = age and it should work

Korlat

Level 25 , Gasteiz, Basque Country, Spain

18 March 2022, 11:32

Hello, you've don't create new object Person in the adjustAge method. Try, simply, to make the increment in the age variable that they give you. Excuse my horrible english.