[SalesForce] Simple Apex class to return a list of strings

I'm writing a simple Apex class as part of the new Salesforce Trailhead developer course. Here's what I'm trying to do:

Create an Apex class that returns an array (or list) of formatted strings ('Test 0', 'Test 1', …). The length of the array is determined by an integer parameter.

  • The Apex class must be called 'StringArrayTest' and be in the public scope.
  • The Apex class must have a public static method called 'generateStringArray'.
  • The 'generateStringArray' method must return an array (or list) of strings. Each string must have a value in the format 'Test n' where n is the index of the current string in the array. The number of returned strings is specified by the integer parameter to the 'generateStringArray' method.

Here is my code: 

public class StringArrayTest {

    //Public Method
    public static void generateStringArray(Integer length) {

        //Instantiate the list
        String[] myArray = new List<String>(length);

        //Iterate throught the list
        for(Integer i=0;i<myArray.size();i++) {

            //Populate the array
            myArray.add(myArray[i]);

            // Write value to the debug log
            System.debug(myArray[i]);

        } //end loop

    }//end method       
 }// end class

I'm sure it's something very simple I'm doing wrong. When I execute right now it's returning:

expecting a semi-colon, found ''

Best Answer

You can't instantiate a List like that using an integer. You don't need to explicitly specify how much items are going into the list when it is created. Instead, just remove the integer:

//Instantiate the list
String[] myArray = new List<String>();

You're logic in your loop seems to be incorrect as well. Specifically, myArray's size will always be 0 when you instantiate it. Change your loop logic to:

for(Integer i=0;i<length;i++) {
   // code
}

You want to generate a List of strings based on the i variable. You will want to change your internal logic to:

//Populate the array
myArray.add('Test ' + i);

// Write value to the debug log
System.debug(myArray[i]);

Finally, you want to return that Array. You need to change your method so the return type is no longer void by changing its signature:

public static String[] generateStringArray(Integer length)

then it is just a matter of returning that array at the end of your method:

return myArray;

This would bring it all together as:

public class StringArrayTest {
    //Public Method
    public static String[] generateStringArray(Integer length) {
        //Instantiate the list
        String[] myArray = new List<String>();

        //Iterate throught the list
        for(Integer i=0;i<length;i++) {
            //Populate the array
            myArray.add('Test ' + i);

            // Write value to the debug log
            System.debug(myArray[i]);
        } //end loop

        return myArray;
    }//end method       
}// end class

Some more info on Arrays and Lists, Loops, and Class methods for future reference.

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