Receiving errors on Apex class to match fields for two different custom objects - salesforce

Question

I've been stuck for 18 hours on this apex class. I would really appreciate some help to figure out what's wrong. Basically this code should match the fields between two objects and I don't know why I'm receiving the following errors:
Missing return statement required return type: String - Line 2
Expecting '}' but was: 'for' - Line 26
The output should show that when location and position title from Candidate object matches location and title from Position object then it will just show those values that match on a data table in a lightning web component I made on Visual Studio.
I'd like some help improving this code so I can run it on the dev console.
public class Matchposition {
public static String matchPositionsWithCandidate() {
Set<String> statuses = new Set<String> {'New', 'Open'};
List<Position__c> openPositions = [SELECT Id, Name, Location__c, Status__c FROM Position__c WHERE Status__c IN :statuses];
//system.debug(openPositions);
Set<String> openPositionAndLocation = new Set<String>();
Map<String, Position__c> openPositionMap = new Map<String, Position__c>();
for (Position__c position : openPositions) {
openPositionMap.put(position.Name + '-' + position.Location__c, position);
openPositionAndLocation.add(position.Name + '-' + position.Location__c);
}
}
//for(String key : openPositionMap.keySet()) {
// system.debug('*** Start ***');
// system.debug('key :' + key);
// system.debug('value :' + openPositionMap.get(key));
// system.debug('*** End ***');
//}
Map<String, List<Candidate__c>> candidatesMap = new Map<String, List<Candidate__c>>();
List<Candidate__c> candidates = [SELECT Position__c, Location__c, Mobile__c, First_Name__c, Last_Name__c, Email__c FROM Candidate__c];
for (Candidate__c candidate : candidates) {
if(candidatesMap.containsKey(candidate.Position__c + '-' + candidate.Location__c)) {
candidatesMap.get(candidate.Position__c + '-' + candidate.Location__c).add(candidate);
} else {
candidatesMap.put(candidate.Position__c + '-' + candidate.Location__c, new List<Candidate__c> {candidate});
}
}
system.debug('*************** OPEN POSITIONS ***************');
for (String key : openPositionAndLocation) {
system.debug('====> ' + openPositionMap.get(key).Name);
if(candidatesMap.containsKey(key)) {
system.debug('***** Candidates *****');
for(Candidate__c candidate : candidatesMap.get(key)) {
system.debug('------- Name : ' + candidate.First_Name__c + ' ' + candidate.Last_Name__c);
system.debug('------- Email : ' + candidate.Email__c);
system.debug('------- Mobile : ' + candidate.Mobile__c);
}
} else {
system.debug('********* No Candidates');
}
}

Answer 1

One issue you certainly have, apropos of nothing else, is overall structure. Removing the actual lines of code, here's how your class is laid out now:
public class Matchposition {
public static String matchPositionsWithCandidate() {
// Code here
}
// more code here - problem!
}
You have much of your logic loose in the body of your class, which is not valid in Apex. Additionally, the code in the class body references variables declared inside the method matchPositionsWithCandidate(), which are scoped (visible) to that method.
matchPositionsWithCandidate() is also declared to return a string, but in fact returns nothing at all.
Since you're not returning any data anywhere, one step you can take to try to get this code running is to ensure that all of your logic is inside the scope (the curly braces) of the method matchPositionsWithCandidate(), and declare that method to return void, not String.
You may also have unbalanced braces - it looks like there is one missing after the final else - if it wasn't simply omitted in the copy and paste.
I'm not sure why this code exists. While much of the logic is correct, it makes far more sense to model your data with a relationship between Candidate__c and Position__c, rather than just storing a name in both positions. Then, you don't need any "matching" code at all - just a simple SOQL relationship query.