Java. Execute a class from other class?

Question

I'm very new in Java and I have a small question. I believe it is due to some misunderstanding of the concepts.

So, I have main class menu:

/**
 * menu.java
*/
public class menu {
    public void run() {
        println ("1. Option#1.");
        println ("2. Option#2.");
        println ("============");

        int choose = readInt("Enter a choice:");
        if (choose == 1) {
        // QUESTION>>>>>   // ### how can I call class option1.java here?

    }
}


/**
 * option1.java
*/
public class option1 { 
   public void scriepedos () { 
        setFont("Times New Roman-24");
        while (true) {
                String str = readLine("Please enter a string: "); 
                if (str.equals("")) break; 
                String rev = reverseString(str); 
                println(rev);
        }
    }

    private String reverseString(String str) {
        String result = "";
        for (int i=0; i<str.length();i++){
            result=str.charAt(i)+result;
        }
        return result.toLowerCase();
    }
}

Many thanks in advance. Leo

Answer 1

You need an instance of option1 to call upon eg

option1 o1 = new option1();
o1.scriepedos();

Alternatively you can make the method static . That means that you don't need the corresponding instance of the object eg in option1.java

public static void scriepedos () { ...

then in main.java

option1.scriepedos();

The above isn't very OO. You're now making use of the fact that you can have an object encapsulating state etc. and is a much more procedural style.

Notes:

1. I suspect you need a public static void main() method to invoke the above
2. Java style would require class names to be camel-cased. eg Option1 , Main

Answer 2

You can not call to class. You have to create new object of class and call it's methods like below :

Option1 op1 = new Option1();
// call any Option1 method
op1.scriepedos();