Java -- The return type of a function is "String" but it can return both String and int data types

Issue

class Student {
    String name;
    int age;

    public void setInfo(String n, int a) {
        this.name = n;
        this.age = a;
    }

    public String getInfo() { // Notice the "String" data type in this function
        return (this.name + " " + this.age);  // "this.age" is a "int" data type but the function is supposed to be returning only "String" data type, right?
    }
}

public class OOPS {
    public static void main(String args[]) {
        Student s1 = new Student();

        s1.setInfo("John", 24);
        System.out.println(s1.getInfo());
    }
}

Here is the output: Click me to see the output

The next thing I tried to do was replace "String" with "int" in the function.

Like this:

public int getInfo() {      
     return (this.name + " " + this.age); 
}

It throws this error: Click me to see the error

The question is why is it so?

Solution

The string concatenation in your code:

return ( this.name + " " + this.age );

… implicitly generates a string from your int member field, this.age.

That is equivalent to a call to String.valueof:

return ( this.name + " " + String.valueOf( this.age ) );

See Converting Numbers to Strings in the Java Tutorials provided by Oracle free of cost.

Answered By - Basil Bourque