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

You can call the instance method of class by creating an object via Object reference. — KV Prajapati
– KV Prajapati, Commented Aug 16, 2012 at 8:21
but the new problem it is that nothing happened when I call the instance method. This is because "scriepedos" it's void ? — Leonard Lepadatu
– Leonard Lepadatu, Commented Aug 16, 2012 at 9:28

Brian Agnew · Accepted Answer · 2012-08-16 08:20:55Z

2

You need an instance of option1 to call upon e.g.

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 e.g. 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:

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

answered Aug 16, 2012 at 8:20

Brian Agnew

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2 Comments

Leonard Lepadatu Over a year ago

Thank you all! About notes: 1. I realy have but I simplify the code :); 2. Thats are not my real class name :), but Thank you!

Leonard Lepadatu Over a year ago

I do it but nothing it's happened when I call the instance option1.scriepedos(). This it's because scriepedos is "void" type ?

Nandkumar Tekale · Accepted Answer · 2012-08-16 08:23:28Z

1

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();

answered Aug 16, 2012 at 8:23

Nandkumar Tekale

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