Instance variables in Java - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an instance variable named age of type int.

Java

public class Person {
    [1] age;
}

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Astatic

Bint

Cvoid

Dfinal

Attempts:

3 left

💡 Hint

Common Mistakes

Using static makes the variable shared by all objects, not an instance variable.

Using void is only for methods, not variables.

The keyword int declares the variable age as an integer instance variable.

2fill in blank

medium

Complete the code to assign the value 25 to the instance variable age inside the constructor.

Java

public class Person {
    int age;
    public Person() {
        [1] = 25;
    }
}

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Athis.age

Bage()

CPerson.age

Dstatic age

Attempts:

3 left

💡 Hint

Common Mistakes

Using age() which looks like a method call.

Using Person.age which is for static variables.

Use this.age to refer to the instance variable age inside the constructor.

3fill in blank

hard

Fix the error in the code by completing the declaration of the instance variable name of type String.

Java

public class Person {
    [1] name;
}

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Afinal int

Bstatic String

Cvoid String

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using static String makes it a class variable, not an instance variable.

Using void String is invalid syntax.

The correct way to declare an instance variable of type String is simply String name;.

4fill in blank

hard

Fill both blanks to complete the constructor that sets the instance variables name and age.

Java

public class Person {
    String name;
    int age;

    public Person(String name, int age) {
        this.name = [1];
        this.age = [2];
    }
}

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Aname

Bage

C"name"

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning string literals like "name" instead of the parameter name.

Assigning zero 0 instead of the parameter age.

The constructor parameters name and age are assigned to the instance variables using this.name = name; and this.age = age;.

5fill in blank

hard

Fill all three blanks to complete the method that returns a description using instance variables name and age.

Java

public class Person {
    String name;
    int age;

    public String getDescription() {
        return [1] + " is " + [2] + [3];
    }
}

Drag options to blanks, or click blank then click option'

Aname

Bage

C " years old"

D"Hello"

Attempts:

3 left

💡 Hint

Common Mistakes

Using string literals instead of variables for name or age.

Forgetting to add the descriptive text like " years old".

The method returns a string combining the instance variable name, the integer age, and the string literal " years old".