Having trouble calling a method to edit a string from another class in java

Question

I've got a simple java program that is supposed to take the specified characters in a string and print them back out to the user by doing everything within a secondary method in a secondary class while taking input from the user in the first class.

The problem that I'm having is that when I try to invoke the secondary method in my main method, I get an error that says "The method copy(String) is unidentified for my main method.

My code for the main method is:

    System.out.println("Copying - Enter a string");
            String currentString = input.next();
            System.out.println("The current string is: " + currentString);
            System.out.println("Enter the starting position");
            int startPosition = input.nextInt();
            System.out.println("Enter one past the ending position");
            int onePastLastPosition = input.nextInt();
            System.out.println("The new string is: " + copy(currentString));

And for the copy method is:

public static String copy(String currentString, int startPosition, int onePastLastPosition) { 
        currentString = currentString.substring(startPosition, onePastLastPosition); 
        return currentString;
    }

So for example, what the code is supposed to do, is if I input a string "abcd", it returns back to me "bc", but the system gets hung up on the last line in the first method. Any help with understanding where I went wrong, and how to fix it in the future would be much appreciated.

Answer 1

You didn't provide the method the necessary parameters for it to execute properly.

Method copy is accepting three parameters: currentString , startPosition , onePastLastPosition as per the parameters specified:

public static String copy(String currentString, int startPosition, int onePastLastPosition) {

So you should be calling the method like so:

System.out.println("The new string is: " + copy(currentString, startPosition, onePastLastPosition));

Test Run

Copying - Enter a string
spectric
The current string is: spectric
Enter the starting position
1
Enter one past the ending position
2
The new string is: p

Answer 2

Your copy method is in different class.You have to create the second class instance in first class to call the second class function.

First class

System.out.println("Copying - Enter a string");
        ....   
System.out.println("The new string is: " + 
SecondClass.copy(currentString));

P/S : Make sure the number of the parameters are correct.

Answer 3

您的copy方法是static ，因此您应该使用类前缀调用该方法，并传递您声明的其他参数（ startPosition 、 onePastLastPosition ）。

System.out.println("The new string is: " + YourClassName::copy(currentString, startPosition, onePastLastPosition))

Answer 4

Two things.

• your parameters to copy are different than the method signature shows.
• you should be calling Copy as a static by prefixing the name of the containing class.

Answer 5

The copy method requires 3 parameters, but you have only provided 1. Add the other two:

copy(currentString, startPosition, onePastLastPosition)

---

Add an import statement for the copy method:

import static SecondClass.copy;

Or qualify the method:

SecondClass.copy(currentString, startPosition, onePastLastPosition)