How to represent a value using object (Not representing the object as a whole)

Question

How can I represent a value via an object(A custom value)

Hello, I would like to ask how to represent a value using object (I am not talking about referring the the object itself, but represent a custom value.)

This is one of the class that I found having a custom value

It is wrapper class. When I try to print a wrapper class object (Integer for example),it prints out the value that I stored in it.

package Testing;
public class test {
    static Integer one = 1;
    public static void main(String[] args) {
    System.out.println(one);
}
}

So, I create an Integer object, and when I print it, it prints the value that I stored in it.

So,

I wanted to understand how it work. Sorry if it is a build in feature (that can't be coded in regular java)
Thank you :)

Answer 1

I will tell you the internal logic about System.out.println().

this is println(Object o) method.

public void println(Object x) {
        String s = String.valueOf(x); // In summary, the output string in this line is determined.
        synchronized (this) {
            print(s);
            newLine();
    }
}

this is valueOf(Object o) method.

public static String valueOf(Object obj) {
        return (obj == null) ? "null" : obj.toString(); // Here you can see that obj's toString() method is called.
}

In summary, when you println() with an object, it prints according to the return value of the toString() method in the object.

---

Now, let's see your case about Integer class.

private final int value;

public String toString() {
        return toString(value);
}

public static String toString(int i) {
        if (i == Integer.MIN_VALUE)
            return "-2147483648"; // If integer is MinValue, the minimum value is returned as a string.
        int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
        char[] buf = new char[size];
        getChars(i, size, buf);
        return new String(buf, true); // Creates a char array, assembles numbers, converts them to strings, and returns them.
}